Hard Polymer Research Articles

Superior damage tolerance observed in interpenetrating phase composites composed of aperiodic lattice structures

Interpenetrating Phase Composite (IPC) metamaterials, based on lattice topologies, have garnered significant attention as advanced materials for structural applications. However, conventional IPCs, which rely on periodic lattice unit cells, are prone to catastrophic failure due to their global deformation modes. To overcome this limitation, we present a novel IPC design utilizing aperiodic truss unit cells, inspired by the elusive “Einstein” monotile pattern. Our concept is demonstrated through IPC 3D printed via polymer jetting, using a hard polymer as the lattice filler and a soft polymer as the matrix. The distinctive mechanical properties of IPCs are characterized through single and cyclic quasi-static compression testing. Our findings demonstrate that aperiodic IPCs enable progressive deformation with gradual compression stress plateaus. Additionally, aperiodic IPCs exhibit remarkable damage tolerance, retaining 67.59 % of residual energy absorption and 73.83 % of ultimate strength after multiple cyclic compressions up to 30 % strain. These mechanisms are attributed to the synergistic deformation of interconnected unit cells, which lead to self-adjusting plastic collapse, progressive displacement evolution and delocalized deformation. This aperiodic concept paves the way for developing high-performance cushioning protection materials.

Random close packing of semi-flexible polymers in two dimensions: Emergence of local and global order.

Through extensive Monte Carlo simulations, we systematically study the effect of chain stiffness on the packing ability of linear polymers composed of hard spheres in extremely confined monolayers, corresponding effectively to 2D films. First, we explore the limit of random close packing as a function of the equilibrium bending angle and then quantify the local and global order by the degree of crystallinity and the nematic or tetratic orientational order parameter, respectively. A multi-scale wealth of structural behavior is observed, which is inherently absent in the case of athermal individual monomers and is surprisingly richer than its 3D counterpart under bulk conditions. As a general trend, an isotropic to nematic transition is observed at sufficiently high surface coverages, which is followed by the establishment of the tetratic state, which in turn marks the onset of the random close packing. For chains with right-angle bonds, the incompatibility of the imposed bending angle with the neighbor geometry of the triangular crystal leads to a singular intra- and inter-polymer tiling pattern made of squares and triangles with optimal local filling at high surface concentrations. The present study could serve as a first step toward the design of hard colloidal polymers with a tunable structural behavior for 2D applications.

Fabricating Multiphasic Angiogenic Scaffolds Using Amyloid/Roxadustat-Assisted High-Temperature Protein Printing.

Repairing multiphasic defects is cumbersome. This study presents new soft and hard scaffold designs aimed at facilitating the regeneration of multiphasic defects by enhancing angiogenesis and improving cell attachment. Here, the nonimmunogenic, nontoxic, and cost-effective human serum albumin (HSA) fibril (HSA-F) was used to fabricate thermostable (up to 90 °C) and hard printable polymers. Additionally, using a 10.0 mg/mL HSA-F, an innovative hydrogel was synthesized in a mixture with 2.0% chitosan-conjugated arginine, which can gel in a cell-friendly and pH physiological environment (pH 7.4). The presence of HSA-F in both hard and soft scaffolds led to an increase in significant attachment of the scaffolds to the human periodontal ligament fibroblast (PDLF), human umbilical vein endothelial cell (HUVEC), and human osteoblast. Further studies showed that migration (up to 157%), proliferation (up to 400%), and metabolism (up to 210%) of these cells have also improved in the direction of tissue repair. By examining different in vitro and ex ovo experiments, we observed that the final multiphasic scaffold can increase blood vessel density in the process of per-vascularization as well as angiogenesis. By providing a coculture environment including PDLF and HUVEC, important cross-talk between these two cells prevails in the presence of roxadustat drug, a proangiogenic in this study. In vitro and ex ovo results demonstrated significant enhancements in the angiogenic response and cell attachment, indicating the effectiveness of the proposed design. This approach holds promise for the regeneration of complex tissue defects by providing a conducive environment for vascularization and cellular integration, thus promoting tissue healing.

Bioinspired soft-hard interfaces fabricated by multi-material additive manufacturing: A fracture mechanics investigation using essential work of fracture

This study employs the Essential Work of Fracture (EWF) concept to evaluate the interfacial fracture toughness of bioinspired interfaces between soft and hard polymer phases. The experimental framework utilizes a model material system with Polylactic Acid (PLA) as the hard phase and Thermoplastic Polyurethane (TPU) as the soft phase. Employing the Fused Filament Fabrication (FFF) technique, bioinspired sutural interfaces are created, characterized by interpenetrating soft and hard protrusions. The modulation of a critical parameter in the FFF process enables the variation of interpenetration length of protrusions at the interface, thereby achieving a spectrum of interfacial strength and toughness. The determination of essential work of fracture from double edge notch tension samples, with varied ligament sizes, allows for the specific EWF measurement. This specific EWF is found to align with the initiation value of plane strain interfacial fracture toughness obtained through the Double Cantilever Beam (DCB) test. Therefore, the proposed approach asserts the elimination of the need for complex interfacial fracture tests, such as DCB. A noteworthy discovery is the establishment of a correlation between specific plastic energy dissipation and protrusion length. This correlation suggests an increased plastic dissipation with longer protrusions within the investigated bioinspired interface. Due to this heightened plastic energy dissipation, the shape of the interfacial nominal stress-displacement curves demonstrates substantial dependence on interface morphology, shifting from a triangular to a trapezoidal shape as protrusion length increases. These findings offer valuable insights into the mechanics of bioinspired interfaces, presenting a more efficient and nuanced approach to characterizing their fracture properties.

Multiscale Computational and Artificial Intelligence Models of Linear and Nonlinear Composites: A Review

Herein, state‐of‐the‐art multiscale modeling methods have been described. This research includes notable molecular, micro‐, meso‐, and macroscale models for hard (polymer, metal, yarn, fiber, fiber‐reinforced polymer, and polymer matrix composites) and soft (biological tissues such as brain white matter [BWM]) composite materials. These numerical models vary from molecular dynamics simulations to finite‐element (FE) analyses and machine learning/deep learning surrogate models. Constitutive material models are summarized, such as viscoelastic hyperelastic, and emerging models like fractional viscoelastic. Key challenges such as meshing, data variability and material nonlinearity‐driven uncertainty, limitations in terms of computational resources availability, model fidelity, and repeatability are outlined with state‐of‐the‐art models. Latest advancements in FE modeling involving meshless methods, hybrid ML and FE models, and nonlinear constitutive material (linear and nonlinear) models aim to provide readers with a clear outlook on futuristic trends in composite multiscale modeling research and development. The data‐driven models presented here are of varying length and time scales, developed using advanced mathematical, numerical, and huge volumes of experimental results as data for digital models. An in‐depth discussion on data‐driven models would provide researchers with the necessary tools to build real‐time composite structure monitoring and lifecycle prediction models.

Light-driven soft microrobots based on hydrogels and LCEs: development and prospects.

In the daily life of mankind, microrobots can respond to stimulations received and perform different functions, which can be used to complete repetitive or dangerous tasks. Magnetic driving works well in robots that are tens or hundreds of microns in size, but there are big challenges in driving microrobots that are just a few microns in size. Therefore, it is impossible to guarantee the precise drive of microrobots to perform tasks. Acoustic driven micro-nano robot can achieve non-invasive and on-demand movement, and the drive has good biological compatibility, but the drive mode has low resolution and requires expensive experimental equipment. Light-driven robots move by converting light energy into other forms of energy. Light is a renewable, powerful energy source that can be used to transmit energy. Due to the gradual maturity of beam modulation and optical microscope technology, the application of light-driven microrobots has gradually become widespread. Light as a kind of electromagnetic wave, we can change the energy of light by controlling the wavelength and intensity of light. Therefore, the light-driven robot has the advantages of programmable, wireless, high resolution and accurate spatio-temporal control. According to the types of robots, light-driven robots are subdivided into three categories, namely light-driven soft microrobots, photochemical microrobots and 3D printed hard polymer microrobots. In this paper, the driving materials, driving mechanisms and application scenarios of light-driven soft microrobots are reviewed, and their advantages and limitations are discussed. Finally, we prospected the field, pointed out the challenges faced by light-driven soft micro robots and proposed corresponding solutions.

Combined effect of acetoacetoxy - Amine interparticle crosslinking and different TG polymer phases to obtain high performance waterborne wood coatings

Two strategies to overcome the film formation dilemma of waterborne binders are combined to produce hard coatings at low temperature without the need of high amounts of coalescing agents, namely crosslinking during film formation and the mixture of soft and hard polymer phases. The crosslinking chemistry used is the one between acetoacetoxy functionalized latexes and amine functionalized ones. Crosslinked and non-crosslinked binder films are investigated by DMTA analysis to study the crosslinking degree and the degree of interdiffusion between polymeric phases in each case. TEM and AFM analysis are also used to support the results obtained by DMTA. The prepared binders are then incorporated in a pigmented coating formulation and tested for wood coating applications such as hardness development, blocking resistance, water resistance and wet adhesion. The relative effect of crosslinking and the presence of different TG phases are investigated by making a comparative study with non-crosslinked paints.

The influence of phenolic resin modified by cardanol on improving the processability of PVC

Polyvinyl chloride (PVC) is a kind of plastic widely used in different industries, and it is a hard and brittle polymer that requires the use of plasticizers to improve processability. Phthalates are small molecule plasticizers of PVC, which are easy to volatilize and migrate while improving the processing properties of PVC. We propose alternatives based on phenolic resin prepolymer modified by cardanol (CPF), which were added to PVC as reactive plasticizer and can improve the processability of PVC. The effects of CPF on the rheological properties and migration resistance of plasticized PVC were studied, and the changes in the physical properties of blends were also discussed. The results showed that the viscosity of PVC melt can be reduced by two orders of magnitude by adding 30 wt% prepolymers at 180°C compared with PVC without CPF, which indicated that CPF can be used to reduce the processing temperature of PVC. The test results of migration resistance showed that the mass loss rate of the blend with 30 wt% prepolymers was less than 1 wt% after curing, however, the mass loss rate of the blend with 30 wt% dioctyl phthalate (DOP) was more than 12% after 5 days of testing. When the PVC/CPF mass ratio was between 60/40-70/30, the maximum values of tensile strength and elastic modulus are 64.4 MPa and 3.2 GPa, respectively, which showed the addition of CPF could significantly improve the tensile strength and elastic modulus of the blend system compared with PVC without CPF. Especially, the thermal stability of CPF is better than that of DOP, CPF exhibits the maximum thermal decomposition temperature (410°C), higher than that of DOP (170°C), which can adapt to higher processing temperature.

A Polytetrafluoroethylene@Polyacrylonitrile core-shell composite with high tribological performance

As a lubricating additive, polytetrafluoroethylene (PTFE) exhibited poor wear resistance, high wear rate and weak adhesion strength, which restricted its application in the area of lubrication and wear protection. In this paper, we prepared a PTFE-based core-shell composite (PTFE@PAN) composed of PTFE core and polyacrylonitrile (PAN) shell through an emulsion polymerization method. The PTFE core with diameter of about 80–100 nm was wrapped by the PAN shell with the thickness of about 50–60 nm. The PTFE@PAN core-shell composite present better dispersion stability in lubricating oil (poly-α-olefin 6, PAO6) than PTFE. Additionally, the PTFE@PAN composite dispersed in PAO6 exhibited significantly reduction in friction coefficient and wear scar width up to 50 % and 25 % compared to PTFE, respectively. Meanwhile, the wear volume of PTFE@PAN composite under a load of 200 N was 4.855 × 104 μm3, was merely one twenty-seventh of that of PTFE (130.6 × 104 μm3). In comparison to conventional oil lubricants, this enhanced tribological properties of PTFE@PAN composite were conducive to a homogeneous transfer film composed of the dual-phase hard polymer (PAN) and soft PTFE polymer (PTFE). Compared with PTFE, the lower surface hardness and better flexibility of PAN shell led to deformation and gap filling with the entanglement and motion of the molecular chains, which could reduce the scratches and decline the abrasive wear of the rubbing surface significantly in the course of the friction process on a rough surface under the high load. That results also suggested that the PTFE@PAN core-shell composite will be a potential lubricating and wear-resistant additive.

Mechanically strong, soft yet tough, tear-resistant and room-temperature healable elastomers via dynamic biphasic hard segment strategy for flame retardant application

Due to the inherent weak molecular chain migration ability of hard polymer materials, leads to their inability to recover after damage. Hence, a novel approach as the “dynamic biphasic hard segment” strategy is proposed. This strategy involves introducing hard segments with both hard and soft phase structures into the molecular chain to balance high mechanical strength with self-healing properties. The essential features of dynamic biphasic hard segments include: (Ⅰ) asymmetric continuous loose structure, (Ⅱ) controllable binding energy strength, (III) sequential dissociation and recombination of multiple hydrogen bonds. To synthesize supramolecular polyurethane elastomers (PUMI-A3D7) based on this dynamic biphasic hard segment strategy. PUMI-A3D7 exhibits high mechanical strength, toughness, notch insensitivity and room temperature self-healing ability. Specifically, the mechanical tensile strength of PUMI-A3D7 is 26.59 MPa, and 96.54% of its original mechanical properties can be restored within 24 h after a fracture. Using the superior properties of PUMI-A3D7 as the matrix, a flexible room temperature repairable flame-retardant composite (PUMI-A3D7/Al(OH)3/GP) is developed. PUMI-A3D7/Al(OH)3/GP possesses both room temperature self-healing function and flame-retardant properties. Notably, few studies have been conducted on repairable flexible flame-retardant materials. The combination of self-healing and flame-retardant properties provides valuable guidance for the development of multi-functional materials in the future.

(Invited) Hard Polymers: Irreversible Synthetic Routes to Ultra-Strong Two-Dimensional Polymers in Bulk

Polymers that extend covalently in two dimensions have attracted recent attention as a means of combining the mechanical strength and in-plane energy conduction of conventional two-dimensional (2D) materials with the low densities, synthetic processability, and organic composition of their one-dimensional counterparts. Efforts to date have proven successful in forms that do not allow full realization of these properties, such as polymerization at flat interfaces or fixation of monomers in immobilized lattices. A frequently employed synthetic approach is to introduce microscopic reversibility, at the cost of bond stability, to achieve 2D crystals after extensive error correction. Herein we demonstrate a synthetic route to 2D irreversible polycondensation directly in the solution phase, resulting in a covalently bonded 2D polymer that is chemically stable and highly processable. Further fabrication offers highly oriented, free-standing films which exhibit exceptional 2D elastic modulus and yield strength at 12.7 ± 3.8 GPa and 488 ± 57 MPa, respectively. The highly planar asymmetry of 2D molecules is evidenced by chemical atomic force microscopy, and molecular alignment in nanofilms is supported by a polarized photoluminescence centered at 580 and 680 nm from different dipole transitions. We have also made substantial progresses in the theory of 2D chain growth. We performed a chemical kinetic simulation study to understand 2D polymerization in homogeneous solution with irreversible chemical steps. We show that reaction sites for polymerization in 2D always scale unfavourably compared to 3D, growing as molecular weight to the 1/2 power versus 2/3 power for 3D. However, certain mechanisms can effectively suppress out-of-plane defect formation and subsequent 3D growth. We consider two such mechanisms, which we call bond-planarity and templated autocatalysis. In the first, although single bonds can easily rotate out-of-plane to render polymerization in 3D, some double-bond linkages prefer a planar configuration. In the second mechanism, stacked 2D plates may act as van der Waals templates for each other to enhance growth, which leads to an autocatalysis. When linkage reactions possess a 1000:1 selectivity (γ) for staying in plane versus rotating, solution-synthesized 2D polymers can have comparable size and yield with those synthesized from confined polymerization on a surface. Autocatalysis could achieve similar effects when self-templating accelerates 2D growth by a factor β of 106. A combined strategy relaxes the requirement of both mechanisms by over one order of magnitude. We map the dependence of molecular weight and yield for 2D polymer on the reaction parameters, allowing experimental results to be used to estimate β and γ. Our calculations show for the first time from theory, the feasibility of producing two-dimensional polymers from irreversible polymerization in solution. These new synthetic routes, now experimentally validated, provides exciting, new opportunities for 2D polymers in applications ranging from composite structures to barrier coating materials.

Modelling cracking during film formation of soft core/hard shell latexes

Waterborne dispersions of hybrid polymer particles consisting of a soft core covered by patches of hard polymer (soft core-hard “shell”) are very promising to overcome the film formation paradox (formation of mechanically strong films at low temperature). However, the presence of hard phase at the exterior of the particles creates stresses during film formation that often results in cracking of the films. Due to the technological importance, mathematical modelling of cracking during drying of waterborne dispersions is an active area of research. These models developed analytical expressions that predict cracking for homogeneous and hard core-soft shell dispersions. However, they cannot justify the experimental results obtained with soft core-hard “shell” dispersions. As the development of analytical equations for film formation from soft core-hard “shell” dispersions looks an insurmountable challenge, in this work, a different strategy was used and particle deformation and stress generation were calculated by numerically solving a modified Navier-Stokes equation. A good agreement between experimental results and model predictions was achieved.

Research on Waste Combustion in the Aspect of Mercury Emissions.

The topic of waste combustion/co-combustion is critical, given the increasingly restrictive legal regulations regarding its environmental aspects. In this paper, the authors present the test results of selected fuels of different compositions: hard coal, coal sludge, coke waste, sewage sludge, paper waste, biomass waste and polymer waste. The authors conducted a proximate and ultimate analysis of the materials and mercury content in them and their ashes. An interesting element of the paper was the chemical analysis of the XRF of the fuels. The authors conducted the preliminary combustion research using a new research bench. The authors provide a comparative analysis of pollutant emissions-especially mercury emission-during the combustion of the material; this is an innovative element of this paper. The authors state that coke waste and sewage sludge are distinguished by their high mercury content. The value of Hg emission during the combustion depends on the initial mercury content in the waste. The results of the combustion tests showed the adequacy of mercury release compared to the emissions of other compounds considered. Small amounts of mercury were found in waste ashes. The addition of a polymer to 10% of coal fuels leads to a reduction in mercury emissions in exhaust gases.

Synthesis of network polymers by means of ring-opening addition reaction of a tri-aziridine and dicarboxylic acid compounds

Polyethylenimine (PEI) is widely used in various products. Development of PEI network polymers would expand the application of the PEI. Ring-opening homo-polymerization of tri-aziridine compounds yielded the PEI-based hard network polymers derived from high dense crosslinking structure. Introduction of the flexible unit in the polymer network should be effective to control the mechanical properties of the resulting network polymers. In the present study, ring-opening addition reactions between a tri-aziridine, 2,2-bishydroxymethylbutanol-tris[3-(1-aziridinyl)propionate] (3AZ), and α,ω-dicarboxylic acid, RCAn (HOOC-(CH2)n-COOH): succinic acid (RCA2), adipic acid (RCA4), dodecanedioic acid (RCA10), or α,ω-dicarboxylic acid with ether linkage, ECAm (HOOC-(CH2OCH2)m-COOH); diglycolic acid (ECA1), 3,6,9-triocaundecanedionic acid (ECA3), poly(ethylene glycol) bis(carboxymethyl) ether (ECA4) were conducted to yield the polymers with controlled network structure. The reactions at room temperature in N,N-dimethylformamide successfully yielded gels. Young's modulus of the gel decreased with increasing in the chain length of the dicarboxylic acid used. The reaction of 3AZ with RCA4 in acetone or ethanol (EtOH) induced phase separation and produced porous polymers. The reactions with oxalic acid (RCA0), glutaric acid (RCA3), suberic acid (RCA6), ECA1, ECA3, or ECA4 in EtOH also yielded the porous polymers. The morphology in the porous polymers was formed by connected particles. The Young's modulus of the porous polymer also decreased with increasing in the chain length of the dicarboxylic acid used. The resulting porous polymers absorbed various solvents, such as acetone, water, dichloromethane, and chloroform. Hydrophobicity and hydrophilicity of the porous polymers can be controlled by the molecular structure of the dicarboxylic acid in the polymer networks.

MP68-20 RELIABLE INSTRUMENT COUNTER (RIC) FOR UROLOGIC PROCEDURES

You have accessJournal of UrologyCME1 Apr 2023MP68-20 RELIABLE INSTRUMENT COUNTER (RIC) FOR UROLOGIC PROCEDURES Catherine Nguyen, Michael Fink, Cayman Myers, Kayla Dunch, Daniel Aguilar, Jack Gibbs, Shelby McCoy, Hannah Bachtel, Chester Koh, and Charles Peak Catherine NguyenCatherine Nguyen More articles by this author , Michael FinkMichael Fink More articles by this author , Cayman MyersCayman Myers More articles by this author , Kayla DunchKayla Dunch More articles by this author , Daniel AguilarDaniel Aguilar More articles by this author , Jack GibbsJack Gibbs More articles by this author , Shelby McCoyShelby McCoy More articles by this author , Hannah BachtelHannah Bachtel More articles by this author , Chester KohChester Koh More articles by this author , and Charles PeakCharles Peak More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003331.20AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Retained sponges and surgical instruments with urologic procedures can have significant consequences on patient outcomes such as increased morbidity, long term disabilities, as well as medicolegal ramifications. The traditional method of ensuring accurate counts for sponges and surgical instruments is manual counting by surgical assistants (i.e. nurses and surgical technicians). However, this method is time-consuming and prone to systemic and human errors which can lead to unidentified retention of instruments. Current technologies for sponge and instrument tracking are limited by cost and accuracy issues. In collaboration with the engineering teams at local engineering schools, we sought to develop an automated surgical instrument counter to increase the accuracy of surgical equipment counts. METHODS: We developed a prototype for the Reliable Instrument Counter (RIC) which performs continuous and automatic counting of surgical instruments using RFID technology. The device consists of a hard polymer tabletop for RFID transparency with three RFID antennas and one multichannel RFID reader. RFID tags were placed on each surgical instrument (7.8mm x 6.8mm x 2.7mm) that were compatible with all methods of instrument sterilization Figure 1). Java-based software was used to automate the count of surgical instruments with a user-friendly interface. Benchtop testing was performed to identify the number of tags needed per instrument and the accuracy of the RIC to count the instruments. RESULTS: The prototype table was developed with the surface divided into zones. The accuracy of detecting tagged instruments averaged 99.03% readability across all zones with only three small areas on the edges of the table that had less than 100% accuracy. Further modifications will involve adjust the mounted location of the RFID reader for improved accuracy. CONCLUSIONS: The RIC can accurately track surgical instruments in real time for urologic procedures, thereby reducing overall OR time and risk of miscounts which translates into reducing overall cost and increasing the safety of patients undergoing urologic surgeries. Source of Funding: FDA grant #1p50FD006428 © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e961 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information Catherine Nguyen More articles by this author Michael Fink More articles by this author Cayman Myers More articles by this author Kayla Dunch More articles by this author Daniel Aguilar More articles by this author Jack Gibbs More articles by this author Shelby McCoy More articles by this author Hannah Bachtel More articles by this author Chester Koh More articles by this author Charles Peak More articles by this author Expand All Advertisement PDF downloadLoading ...

Use of consumer polymer С-РET containers in food production technologies

Different types of consumer containers are used for food packaging: glass, metal, polymer. Polymer containers are in the greatest demand among consumers, due to such advantages as cheapness, small weight, unlimited range of products and volume, pleasant, bright appearance. In the food industry, hard, semi-hard, soft and other consumer polymer containers are used. To use such packaging in technology with high-temperature heat treatment of food products, it must have a heat-resistant barrier layer. Therefore, the object of research is a polymer combined C-PET container, which consists of a semi-rigid container-tray and a heat-resistant multi-layer polymer soft film for its closure. C-PET packaging is made of barrier polymer materials that ensure its mechanical resistance to high temperatures. Therefore, such containers can withstand high-temperature processing and guarantee the tightness of the package and the microbiological stability of the product during storage. Each polymer material has its own specific indicators of heat resistance. The work solves the problem of using the latest polymeric C-PET containers for long-term storage food products, investigates the conditions for preserving the tightness of the containers during heat treatment, which are ensured by the clogging strength parameter. Different types of polymer films for sealing C-PET packaging with the product are also investigated and their mechanical characteristics are compared. In the course of the study, a standard membrane-compensation method was used to measure the clogging strength or depressurization pressure of the package. The essence of the obtained results: the parameters of the use of different types of polymer films of different types were experimentally determined, on the basis of which the type of film was chosen, which ensures the clogging strength of C-PET containers. The results are explained by the fact that the depressurization pressure value obtained will allow to develop scientifically based thermal modes of sterilization and pasteurization for food products in C-PET containers. This will make it possible in practice for enterprises to apply the same regimes and produce high-quality, biologically stable, safe food products with a long shelf life.

4D Biofabrication of Mechanically Stable Tubular Constructs Using Shape Morphing Porous Bilayers for Vascularization Application.

This study reports the fabrication of highly porous electrospun self-folding bilayers, which fold into tubular structures with excellent mechanical stability, allowing them to be easily manipulated and handled. Two kinds of bilayers based on biocompatible and biodegradable soft (PCL, polycaprolactone) and hard (PHB, poly-hydroxybutyrate) thermoplastic polymers have been fabricated and compared. Multi-scroll structures with tunable diameter are obtained after the shape transformation of the bilayer in aqueous media, where PCL-based bilayer rolled longitudinally and PHB-based one rolled transversely with respect to the fiber direction. A combination of higher elastic modulus and transverse orientation of fibers with respect to rolling direction allowed precise temporal control of shape transformation of PHB-bilayer - stress produced by swollen methacrylated hyaluronic acid (HA-MA) do not relax with time and folding is not affected by the fact that bilayer is fixed in unfolded state in cell culture medium for more than 1h. This property of PHB-bilayer allowed cell culturing without a negative effect on its shape transformation ability. Moreover, PHB-based tubular structure demonstrated superior mechanical stability compared to PCL-based ones and do not collapse during manipulations that happened to PCL-based one. Additionally, PHB/HA-MA bilayers showed superior biocompatibility, degradability, and long-term stability compared to PCL/HA-MA.

Polymorphism and Perfection in Crystallization of Hard Sphere Polymers

We present results on polymorphism and perfection, as observed in the spontaneous crystallization of freely jointed polymers of hard spheres, obtained in an unprecedentedly long Monte Carlo (MC) simulation on a system of 54 chains of 1000 monomers. Starting from a purely amorphous configuration, after an initial dominance of the hexagonal closed packed (HCP) polymorph and a transitory random hexagonal close packed (rHCP) morphology, the system crystallizes in a final, stable, face centered cubic (FCC) crystal of very high perfection. An analysis of chain conformational characteristics, of the spatial distribution of monomers and of the volume accessible to them shows that the phase transition is caused by an increase in translational entropy that is larger than the loss of conformational entropy of the chains in the crystal, compared to the amorphous state. In spite of the significant local re-arrangements, as reflected in the bending and torsion angle distributions, the average chain size remains unaltered during crystallization. Polymers in the crystal adopt ideal random walk statistics as their great length renders local conformational details, imposed by the geometry of the FCC crystal, irrelevant.

Bio-inspired hydrogel-polymer brush bi-layered coating dramatically boosting the lubrication and wear-resistance

Surface modification is of great significance in improving the interfacial properties of bioimplants, especially friction and wear of artificial joint materials (e. g. polyetheretherketone, PEEK). Herein, inspired by the layered structure and gradient modulus of natural articular joint, hydrogel-polymer brush bilayered coating was developed to functionalize rigid PEEK (PBHP). The resulting PBHP material showed similar layered structure with natural articular joint. The load-bearing hydrogel layer and lubricating polymer brush layer exhibited corresponding moduli with natural cartilage and superficial biomacromolecules layer, respectively. Tribological tests demonstrated that the obtained material showed outstanding lubrication (friction coefficient<0.07), high load-bearing capability (load>20 N) and excellent wear-resistant capability (sliding cycles>10,000). The “hard PEEK-elastic hydrogel-soft polymer brush” layered material may find potential applications in artificial joint replacement.

Molecular dynamics simulations on photoinduced switchable Tg and self-healing behaviors of azobenzene-containing polymers

Developing polymers with switchable glass transition temperature (Tg) can solve scientific challenges such as fracture healing of polymers with high Tg and processing of hard polymers without plasticizer at room temperature. The azobenzene-containing polymers, or the so-called azopolymers, are smart materials that show photoswitchable Tg and photoinduced motions, which can be used in fabrication of photoactuators. Here, healable and reprocessable models were constructed by using linear azopolymers. Molecular dynamics (MD) simulation was used to study the behaviors of photo-induced bending, self-healing, and directional photofluidization of the azopolymers. A temporary modification of the C–N=N–C dihedral potential was applied to achieve the isomerization of azopolymer by using polymer consistent force-field (PCFF). The simulation results show that isomerization of azobenzene groups can lead to photoswitchable Tg of the azopolymers, which resulting in shape changes and different mechanical responses. Furthermore, the photoswitchable Tg makes the azopolymers much easier to heal under UV irradiation, and restore the mechanical properties under visible light irradiation. Finally, the mechanism of photoliquefaction was investigated, our results imply that the photoinduced trans–cis-trans cycles can reduce the mechanical properties and Tg values of azopolymers.