Crystal Polymer Research Articles

Polyetheretherketone Double Functionalization with Bioactive Peptides Improves Human Osteoblast Response

In recent years, the demand for orthopedic implants has surged due to increased life expectancy, necessitating the need for materials that better mimic the biomechanical properties of human bone. Traditional metal implants, despite their mechanical superiority and biocompatibility, often face challenges such as mismatched elastic modulus and ion release, leading to complications and implant failures. Polyetheretherketone (PEEK), a semi-crystalline polymer with an aromatic backbone, presents a promising alternative due to its adjustable elastic modulus and compatibility with bone tissue. This study explores the functionalization of sandblasted 3D-printed PEEK disks with the bioactive peptides Aoa-GBMP1α and Aoa-EAK to enhance human osteoblast response. Aoa-GBMP1α reproduces 48–69 trait of Bone Morphogenetic Protein 2 (BMP-2), whereas Aoa-EAK is a self-assembling peptide mimicking extracellular matrix (ECM) fibrous structure. Superficial characterization included X-ray photoelectron spectroscopy (XPS), white light interferometer analysis, static water contact angle (S-WCA), and force spectroscopy (AFM-FS). Biological assays demonstrated a significant increase in human osteoblast (HOB) proliferation, calcium deposition, and expression of osteogenic genes (RUNX2, SPP1, and VTN) on functionalized PEEK compared to non-functionalized controls. The findings suggest that dual peptide-functionalized PEEK holds significant potential for advancing orthopedic implant technology.

Process parameter optimization in polymer powder bed fusion of final part properties in polyphenylene sulfide through design of experiments

AbstractThe Additive Manufacturing (AM) modality of Laser-Based Powder Bed Fusion of Polymers (PBF-LB/P) is an established method for manufacturing semi-crystalline polymers. Like other AM processes, the selection of PBF-LB/P process parameters is critical as it has direct effect on final part properties. While prior research has been predominantly focused on polyamides (e.g., nylon 12), there exists a gap in exploring how process parameters affect higher performance polymers, such as polyphenylene sulfide (PPS). This work aims to explore the effects of PBF-LB/P process parameters on PPS parts printed via PBF-LB/P. While prior PBF-LB/P parameter research primarily relies on evaluating energy input to the system through a single numerical value of energy density, this study investigates the interplay of the print parameters within the energy density equation. To achieve these goals, an analysis was performed on the influence of the laser power, hatch spacing, and beam velocity on ultimate tensile strength (UTS), modulus, and crystallinity of printed parts. A Taguchi L8 array was used in balancing the print parameter combinations allowing for isolation of variance to the specific factors and interactions. Through this approach, print parameter combinations that improved UTS and modulus were identified. Additionally, the study revealed that numerically equivalent energy densities did not lead to equivalent performance, underscoring the significance for including the constitutive process parameters within the energy density equation when establishing process property relationships in printing with PBF-LB/P.

Moisture-Triggered 71000-Fold Stiffness Change Materials Via Crystallization and Hydrogen Bonding.

Stiffness change materials have been widely used in soft robots, intelligent adhesives and biomedical minimally invasive devices which can respond to specific stimuli. Compared with stimuli such as light, electricity, magnetism, temperature, and pressure, moisture is a non-toxic, readily available, and inexhaustible triggered source in the atmosphere. However, it is challenging to achieve a stiffness variable material with a large stiffness change using moisture. Traditional sensitive materials usually swell to expand the volume or dissolve to a liquid-like state when absorbing moisture, which is unfavorable for real applications. Herein, we demonstrate a polyvinylamine (PVAm)/polyethylenimine (PEI) composite film with variable stiffness change by moisture absorption and release. PVAm is a semicrystalline polymer with high stiffness and PEI forms intermolecular hydrogen bonding with primary amine groups on PVAm. The synergistic effect of hydrogen bonding and crystallization was maximized when 15 wt % PEI was added to the composite system, resulting in a large stiffness change of up to 7.1 × 104 (0.022 MPa versus 1560.85 MPa) of PVAm/PEI composite film under 25 °C, 95% RH. The crystallinity structure and hydrogen bonding can be broken and reformed by adjusting humidity. As promising variable stiffness polymers, the developed PVAm/PEI composite film is demonstrated as a reconfigurable multitool for shape memory and locking on demand.

Molecular dynamics study on the intramolecular chain-folding pathway at early stage of constrained polymer crystallization

Molecular dynamics study on the intramolecular chain-folding pathway at early stage of constrained polymer crystallization

Supersaturated drug delivery system of albendazole salt-polymer complex for improving oral bioavailability and efficacy anti-secondary E. multilocularis

Based on the supersaturation theory, this study devised two albendazole (ABZ) salt-polymer complexes that enhance the oral bioavailability and efficacy of secondary hepatic alveolar echinococcosis (HAE) in rats. Solid characteristics, microstructure, and stability of ABZ benzenesulfonate (ABZ-BSA) and ABZ methanesulfonate (ABZ-MSA) were evaluated. The equilibrium solubility and intrinsic dissolution rate of salt were measured across different pH environments to determine its potential for generating supersaturation. Polymer crystallization inhibitors were subsequently introduced to assess their impact on sustaining supersaturation. The pharmacokinetics and anti-echinococcosis effects of ABZ were evaluated in healthy SD and HAE rats. The characteristic peaks corresponding to amino acid esters and benzimidazole in the ABZ salt structure either shifted or disappeared, corroborated by PXRD, signifying successful ABZ salt preparation. Furthermore, reductions in the melting point and enthalpy of the salts were observed, along with discernible differences in microstructure compared to ABZ. The drug salts exhibited a significant increase in apparent solubility and intrinsic dissolution rate of ABZ, thus laying the groundwork for supersaturation. Stability assessments indicated that salts were susceptible to moisture absorption, necessitating stringent humidity control measures. Notably, HPMC-AS demonstrated promising capabilities in sustaining supersaturation. Finally, pharmacokinetic analyses revealed a substantial increase in the AUC of ABZ-BSA-H and ABZ-MSA-H by 7.6 and 20.3 times, respectively, compared to ABZ in vivo. After a 30-day once-daily oral administration of the Salts and ABZ to SD rats with hepatic alveolar echinococcosis, the ABZ-BSA-H and ABZ-MSA-H formulation demonstrated a cysts inhibition effect 9.2-fold and 15.3-fold greater than that of ABZ. The salt-HPMC-AS complex could potentially be developed into an improved anti-AE drug therapy. Therefore, the salt-HPMC-AS complex could be developed into an enhanced anti-AE drug therapy.

Conformational Chirality of Single-Crystal Covalent Organic Frameworks.

The crystallization of organic polymers is often hindered by chiral units, hence resulting in chiral organic polymers typically existing as amorphous or partially crystalline phases such as natural rubber and cellulose. Similarly, as an emerging crystalline chiral polymer, chiral covalent organic frameworks (COFs) also inevitably face a delicate balance between chiral units and crystallization, limiting their production and applications in separation, catalysis, and optics. Here, we present a general strategy for producing a series of conformational chiral COFs with high crystallinity through breaking the meso conformation of achiral COFs. Conformational chirality of COF-300 was constructed by involving chiral amino-acid derivative templates during synthesis and was proven to have excellent thermodynamic (200 °C annealing in air) and dynamic stability (61% cell volume change). The stereochemistry of the conformational chiral crystals can be controllably tuned by chiral templates, resulting in wide-range circular dichroism signals from ultraviolet to infrared wavelengths and absorption dissymmetry factors (gabs) varying by up to 300%, with a maximum of gabs = 0.012. This strategy paves the way for stereochemistry modification, property enhancement, and exploration of new applications of crystalline chiral materials.

Investigating single-chain structure during the crystallization process by atomic force microscopy

Crystalline polymers have gained significant traction in various fields owing to their exceptional thermal and mechanical properties. However, the precise mechanism underlying polymer crystallization remains a subject of ongoing debate. In this study, we employed atomic force microscopy (AFM)-based single-molecule force spectroscopy (SMFS), also called nanofishing to investigate the mechanical properties, chain-level structure, and interactions of individual polymer chains, thereby shedding light on the crystallization mechanism. Through control of the crystallization temperature and time of polyethylene oxide (PEO) in solution, in conjunction with differential scanning calorimetry (DSC), we present compelling evidence that polymer crystallization begins with the folding of individual chains into cluster-like forms and the subsequent aggregation of these clusters to form larger crystalline structures. The clusters adopt chain-folding structures with lengths ranging from 7.9 to 9.1 nm at distinct crystallization temperatures. Remarkably, we observed the formation of these clusters in the initial stages, even preceding the 5-min mark. Over time, these clusters progressively aggregate and grow, ultimately leading to lamella structures. This suggests that the primary chain-folding process occurs in the early stage of crystallization, presenting a significant advancement in our understanding of the behavior of polymers at the chain level during the crystallization process. These insights hold immense value in the design and development of advanced crystal-based polymer materials.

Enhancing Mechanophore Activation through Polymer Crystallization.

In the field of polymer mechanochemistry, the activation of mechanophores within linear polymers in the bulk state is often limited by low activation rates. Herein, we demonstrate that the crystallization of polymers can significantly enhance the activation of mechanophores. Employing rhodamine-containing poly(lactic acid) (PLA) and polycaprolactone (PCL) as representative examples, our study reveals that the micromechanical force generated by crystallization is more effective in activating mechanophores than the macroscopic mechanical force induced by compression and ultrasonication, which is particularly pronounced for polymers with low molecular weights. Furthermore, the activation of the mechanophore is found to be positively correlated with the degree of crystallinity and polymer molecular weight, whereas the chirality of polymers does not influence the activation. This study offers new insights into mechanochemical reactions induced by polymer crystallization and provides a novel approach to enhancing mechanochemical reactivity.

Finite strain continuum phenomenological model describing the shape-memory effects in multi-phase semi-crystalline networks

Thermally-driven semi-crystalline polymer networks are capable to achieve both the one-way shape-memory effect and two-way shape-memory effect under stress and stress-free conditions, therefore representing an appealing class of polymers for applications requiring autonomous reversible actuation and shape changes. In these materials, the shape-memory effects are achieved by leveraging the synergistic interaction between one or more crystalline phases and the surrounding amorphous ones that are present within the network itself. The present paper introduces a general framework for the finite strain continuum phenomenological modeling of the thermo-mechanical and shape-memory behavior of multi-phase semi-crystalline polymer networks. Model formulation, including the definition of phase and control variables, kinematic assumptions, and constitutive specifications, is introduced and thoroughly discussed. Theoretical derivations are general and easily adaptable to all cross-linked systems which include two or more crystalline domains or a single crystalline phase with a wide melting range and manifest macroscopically the one-way shape-memory effect and the two-way shape-memory effect under stress and stress-free conditions. Model capabilities are validated against experimental data for copolymer networks with two different crystalline phases characterized by well-separated melting and crystallization transitions. Results demonstrate the accuracy of the proposed model in predicting all the phenomena involved and in furnishing a useful support for future material and application design purposes.

Effect of Metal Nanoparticle on Optical and Thermal Properties of Liquid Crystal Polymer System

In the present study the optical and thermal properties of a Nematic Liquid Crystal Polymer System (NLCPS) dispersed with different concentrations of metal nanoparticles like ZnO, Zn, CuO were investigated using X-Ray Diffraction (XRD), Differential Scanning Calorimetry (DSC) and Fourier Transform Infra-Red (FTIR). The comparison of various parameters of pure NLCPS and its mixture with different concentrations of dopant was carried out to understand the effect of nanoparticles on the optical and thermal properties of NLCPS. Our investigation shows an increase in phase transition temperature after dispersing the metal nanoparticle. The maximum phase transition temperature was found for ZnO. XRD shows a sharp reflection and diffuse scattering is characteristic of crystalline and amorphous phases of conventional semi-crystalline polymers. The presence of functional groups in the nanoparticle dispersed NLCPS has been identified using Fourier Transform Infrared Spectroscopy (FTIR). The investigation may be useful for various energy-efficient devices in addition to display applications.

RVE Simulations of short fiber reinforced polyamide: Direct and inverse matrix parameter identification in view of the semi-crystalline polymer structure

This paper investigates the modeling capabilities of computational homogenization for the mechanical behavior of short fiber reinforced polyamide. Simulations on a representative volume element (RVE) with elastic fibers and an elastic–plastic matrix are compared to tensile experiments on specimens taken in parallel and transversal direction from injection molded plates. In view of the semi-crystalline polymer structure, focus is put on identifying the matrix parameters through two alternative methods:First, the matrix parameters are identified directly using tensile experiments on a non-nucleated and a nucleated unreinforced polyamide. In the RVE computations based on the non-nucleated grade, the composite stress–strain behavior is somewhat underestimated, and with the nucleated grade, the behavior is slightly overestimated. To explain this, the semi-crystalline polymer structure is studied. Polarized light microscopy images reveal that the non-nucleated grade has a coarser and the nucleated grade a finer spherulite structure, compared to the matrix present in the composite. However, the degree of crystallinity measured by differential scanning calorimetry is in a similar range.As an alternative, the matrix parameters are identified inversely by fitting the RVE model to the composite tensile experiments. As uncertainties with respect to the matrix material as well as possibly remaining simplifications in the micromechanical model are compensated for, this reverse engineering approach allows for a very good fit.

In Situ Fluorescent Visualization of the Interfacial Layer of Induced Crystallization in Polyvinyl Chloride.

Despite the remarkable progress in the modification and application of polyvinyl chloride (PVC), developing processing aids for the induced crystallization of PVC and characterizing its interfacial layer remain challenges. Herein, we propose a new polymeric nucleating agent, polyamidea12-graft-styrene-maleic anhydride copolymer (PA12-g-SMA), which possesses high compatibility and crystallinity, effectively improving the crystallinity to 15.1%, the impact strength to 61.03 kJ/m2, and the degradation temperature of PVC to 267 °C through a single and straightforward processing step. Additionally, after the introduction of two different fluorescent sensors in PA12-g-SMA and PVC, the interfacial layer of the induced crystallization can be monitored in situ via a confocal laser scanning microscope (CLSM). This study highlights a rare strategy for significantly enhancing the physical properties of rigid PVC through simply adding a polymeric nucleating agent during processing, while also emphasizing the importance of visualizing the interfacial layer to understand various polymer crystallization processes.

Impact of Ball Milling on the Microstructure of Polyethylene Terephthalate.

Polyethylene terephthalate (PET) is a semi-crystalline polymer that finds broad use. Consequently, it contributes to the accumulation of plastics in the environment, warranting PET recycling technologies. Ball milling is a commonly used technique for the micronization of plastics before transformation. It has also recently been reported as an efficient mixing strategy for the enzymatic hydrolysis of plastics in moist-solid mixtures. However, the effect of milling on the microstructure of PET has not been systematically investigated. Thus, the primary objective of this study is to characterize the changes to the PET microstructure caused by various ball milling conditions. PET of different forms was examined, including pre- and post-consumer PET, as well as textiles. The material was treated to a range of milling frequencies and duration, before analysis of particle size, crystallinity by differential scanning calorimetry and powder X-ray diffraction, and morphology by scanning electron microscopy. Interestingly, our results suggest the convergence of crystallinity to ~30 % within 15 minutes of milling at 30 Hz. These results are consistent with an equilibrium between amorphous and crystalline regions of the polymer being established during ball milling. The combined data constitutes a reference guide for PET milling and recycling research.

Solvent induced crystallization and phase transition of syndiotactic polymethoxystyrene investigated using In situ wide angle X-ray diffraction

Solvent induced crystallization and phase transition is an interesting phenomenon that has been observed in many kinds of semicrystalline polymer. In the case of syndiotactic polystyrene (SPS) which exhibits complicated phase transition behavior, this process may be different when the phenyl rings are substituted by polarity groups. In our previous work, the crystal structures of a series of –OCH3 (OMe) substituted SPS and OMe-SPS/solvent complexes were analyzed (Macromolecules2021, 54, 1881 and Macromolecules2022, 55, 8222). In this particular work, the phase transition behavior of OMe-SPS, especially meta-OMe-SPS with different initial crystalline structures was discussed based on in situ 2-dimensional wide-angle X-ray diffractions (2D-WAXD) in the presence of organic solvent. It is found that meta-OMe-SPS in amorphous state and mesophase shows similar solvent induced phase transition like the cases of SPS. Meanwhile, highly crystalline and oriented meta-OMe-SPS also exhibits organic solvent induced phase transition from β form with planar zigzag conformation into δ form with helical conformation, which has not been observed in SPS. The subsequent heating of meta-OMe-SPS δ and γ forms does not form β form, which is also unlike the situation of SPS δ/δe-γ-α/β transition. The OMe substituted group that changes the polarity of the phenyl rings may be the chemical structure region of affecting the chain conformation energy and phase transition behavior.

A 1D micromechanics-based constitutive model for the thermoviscoelastic behavior of crosslinked semicrystalline shape memory polymers: numerical simulation and experimental validation

Abstract The paper develops a 1D thermoviscoelastic constitutive model for the crystallization- and melting-induced one-way and two-way shape memory effects, as well as isothermal yielding behaviors, of crosslinked semi-crystalline polymers. A micromolecular chain model is proposed to characterize the transition between the amorphous and crystalline phases. Structural equations including a modified Eying model that combine phase transition and viscoelasticity equations are employed to predict the shape memory effects. An extensive experimental campaign has been carried out on poly (ethylene-co-vinyl acetate) based semi-crystalline elastomers to characterize the thermoviscoelastic temperature-stress-strain relations of the material under different loading and rate conditions. Some results guide the determination of the model parameters, while the rest validate the model capabilities. Comparisons with the experimental results show that the model can well reproduce the stress-strain-temperature responses, providing valuable insights for application development.

Surface Engineering of Polymeric Colloidal Crystals by Temperature - Pressure Annealing.

Polymer colloidal crystals (PCCs) have been widely explored as acoustic and optical metamaterials and as templates for nanolithography. However, fabrication impurities and fragility of the self-assembled structures are critical bottlenecks for the device's efficiency and applications. We have demonstrated that temperature-assisted pressure [ annealing results in the mechanical strengthening of PCCs, which improves with the annealing temperature. Here, the enhancement of elastic properties and morphological features of self-assembled PCC's is evaluated using Brillouin light scattering and scanning electron microscopy. The pressure-induced effects on the vibrational modes of PCCs are also illustrated at temperatures well below the polymer glass transition. While the PCCs colloid constituents display reversibility, the PCC material is strongly irreversible in the performed thermodynamic cycle. The effective elastic modulus enhances from 0.7GPa for the pristine sample to 0.8GPa, solely by pressure annealing at room temperature. [ annealing at higher temperatures leads to a maximum effective elastic modulus of 1.7GPa, more than twice the value in the pristine sample. Above a cross-over pressure, 725bar at 348K), the PCCs respond elastically and, hence, reversibly to pressure changes.

Comparison of Au Nanoparticle/Poly(9-vinylcarbazole) Thin-Film Electrogeneration at 3 Distinct Liquid/Liquid Interfaces: Water/1,2-Dichloroethane, /α,α,α-Trifluorotoluene, Or/Ionic Liquid.

Metal nanoparticle (NP) incorporated conductive polymer films are attractive for their mechanical stability for biomedical applications and as heterogeneous electrocatalysis materials. Novel approaches to generate these materials with tunable properties are still being sought. Herein, the interface between two immiscible electrolyte solutions (ITIES) has been employed as a molecularly sharp and reproducible platform for simultaneous Au NP and poly(9-vinylcarbazole) generation. Three interfaces have been compared, including between water|1,2-dichloroethane (w|DCE), water|α,α,α-trifluorotoluene (w|TFT), and water|ionic liquid (w|IL). In this case the IL was P8888TB (tetraoctylphosphonium tetrakis(pentafluorophenyl)borate). 9-Vinylcarbazole (VC) can polymerize via two routes, either propagating through the vinyl substituent or the aryl rings. The former gives rise to a white semiconducting polymer with a wide bandgap, while the latter produces a green, conducting polymer. External potential control through voltammetric cycling was found to generate the film more rapidly favoring heterogeneous electron transfer with formation of the green poly(VC) variant at the ITIES. This was a free-standing film that could be easily removed from the interface. In the absence of external control, white polymer crystals formed within the oil phase spontaneously likely via AuCl4- w → o transfer followed by a homogeneous electron transfer reaction mechanism. Scanning electrochemical microscopy probe approach curve experiments were used to quantify the electroactivity of the film and are complemented by direct conductivity measurements.

Crystallization and crystal morphology of polymers: A multiphase-field study

In this paper, we introduce a coarse-grained model of polymer crystallization using a multiphase-field approach. The model combines a multiphase-field method, Nakamura’s kinetic equation, and the equation of heat conduction for studying microstructural evolution of crystallization under isothermal and non-isothermal conditions. The multiphase-field method provides flexibility in adding any number of phases with different properties making the model effective in studying blends or composite materials. We apply our model to systems of neat PA6 and study the impact of initial distribution of crystalline grains and cooling rate on the morphology of the system. The relative crystallinity (conversion) curves show qualitative agreement with experimental data. We also investigate the impact of including carbon fibers on the crystallization and grain morphology. We observe a more homogeneous crystal morphology around fibers. This is associated with the higher initial volume fraction of crystal grains and higher heat conductivity of the fiber (compared to the polymer matrix). Additionally, we observe that the crystalline grains at the fiber surface grow perpendicular to the surface. This indicates that the vertical growth observed in experiments is merely due to geometrical constraints imposed by the fiber surface and neighbouring crystalline regions.

The Influence of Carbon Fiber on Crystallization and Morphology of Poly(Ether Ketone Ketone) Composites Towards High Rate Thermoplastic Manufacturing Processes

Recent interest in thermoplastic composites for aerospace applications is driven by the need for high-volume manufacturing of materials that display excellent mechanical, thermal, and solvent resistive properties. Specifically, a large component of the composite properties of thermoplastic composites are highly dependent on the crystalline fraction of the semi-crystalline polymer matrix of the reinforced system. This work investigates the melting behavior of poly (ether ketone ketone) (PEKK) and the influence of temperature and fiber on crystallization kinetics and morphology of (PEKK) composites utilizing, differential scanning calorimetry, Velaris-Sefaris modelling, and polarized optical microscopy (POM). Annealing temperatures of 380°C and above were required to fully erase crystalline ordering in the PEKK matrix. Furthermore, carbon fibers accelerated crystallization kinetics in PEKK at a range of temperatures observed via DSC, and Velaris-Sefaris modelling implied a shift from bulk to surface induced nucleation by the addition carbon fiber to the PEKK matrix, reducing activation energy of crystallization events. This nucleation behavior was visually confirmed through POM with observation of transcrystalline domains nucleated from the surface of a single carbon fiber.

The Influence of Carbon Fiber on Crystallization and Morphology of Poly(Ether Ketone Ketone) Composites Towards High Rate Thermoplastic Manufacturing Processes

Recent interest in thermoplastic composites for aerospace applications is driven by the need for high-volume manufacturing of materials that display excellent mechanical, thermal, and solvent resistive properties. Specifically, a large component of the composite properties of thermoplastic composites are highly dependent on the crystalline fraction of the semi-crystalline polymer matrix of the reinforced system. This work investigates the melting behavior of poly (ether ketone ketone) (PEKK) and the influence of temperature and fiber on crystallization kinetics and morphology of (PEKK) composites utilizing, differential scanning calorimetry, Velaris-Sefaris modelling, and polarized optical microscopy (POM). Annealing temperatures of 380°C and above were required to fully erase crystalline ordering in the PEKK matrix. Furthermore, carbon fibers accelerated crystallization kinetics in PEKK at a range of temperatures observed via DSC, and Velaris-Sefaris modelling implied a shift from bulk to surface induced nucleation by the addition carbon fiber to the PEKK matrix, reducing activation energy of crystallization events. This nucleation behavior was visually confirmed through POM with observation of transcrystalline domains nucleated from the surface of a single carbon fiber.