Physical Properties Of Polymers Research Articles

The Influence of Polymer Processing Methods on Polymer Film Physical Properties and Vascular Cell Responsiveness.

Implantable vascular devices typically interface with blood and vascular tissues. Physical properties of device materials and coatings, independent of chemical composition, can significantly influence cell responses and implant success. Here, we analyzed the effect of various polymer processing regimes, using a single implant polymer - poly(ε-caprolactone) (PCL), on vascular endothelial cell (EC), smooth muscle cell (SMC), and platelet response. PCL films were formed by varying three parameters: 1) formation method - solvent casting, melt pressing or spin coating; 2) molecular weight - 50 or 100 kDa; and 3) solvent type - dichloromethane (DCM) or tetrahydrofuran (THF). We quantified the relationship of polymer processing choice to surface roughness, wettability, and bulk stiffness; and to EC adhesion, SMC adhesion, and platelet activity state (PAS). Multiple regression analysis identified which processing method signficantly impacted (F-ratio>p-value; p<0.1) polymer physical properties and vascular cell interaction. Film formation method affected PCL roughness (Rq), wettability (°), and stiffness (MPa) with spin coating resulting in the most wettable (81.8±0.7°), and stiffest (1.12±0.07 MPa; p<0.001) polymer film; however, solvent cast films were the roughest (281±66nm). Molecular weight influenced wettability, with the highest wettability on 50 kDa films (79.7±0.7°; p<0.001) and DCM solvent films (83.0±1.0°; p<0.01). The multiple regression model confidently predicted (F-ratio=9.88; p=0.005) wettability from molecular weight (p=0.002) and film formation method (p=0.03); stiffness (F-ratio=4.21; p=0.05) also fit well tofilm formation method (p=0.02). Film formation method impacted SMC adhesion and platelet activity state, but not EC adhesion, with melt press PCL promoting the highest SMC adhesion (18000±1536 SMCs; p<0.05) and PAS (5.0±0.7 %PAS). The regression model confidently fit SMC adhesion (F-ratio=3.15; p=0.09) and PAS (F-ratio=5.30; p=0.05) to polymer processing choices, specifically film formation method (p<0.03). However, only SMC adhesion had a model that fit well (F-ratio=4.13; p=0.05) to the physical properties directly, specifically roughness and wettability (p<0.04).

Irradiation effects of Cu ions on the electrical and morphological properties of polypropylene

The irradiation of metallic ions on polymeric surfaces may change the chemical, electrical and physical properties of polymers. In this article, we have investigated the effects on the electrical and morphological properties of polypropylene caused by irradiating with copper (Cu) ions generated from laser-produced plasmas. For this purpose Nd: YAG laser (1064 nm) was employed to produce Cu ions. The flux of ions was controlled by varying the number of laser shots in the range 100–400, with a step size of 100. The changes in the electrical conductivity of the irradiated sample were studied using a four-point probe technique, while the surface features were examined by using optical microscopy. The electrical conductivity changed from 4.758 × 10−8 Ω−1 cm−1 to 5.003 × 10−8 Ω−1 cm−1 for unexposed and exposed (with 400 shots) samples, respectively.

Quantitative comparison of photo- and electron-beam polymerizations based on equivalent initiation energy

Electron-beam (EB) and photopolymerization rely on radiation chemistry; however, fundamental differences arise in initiation and energy deposition. Since photopolymerization has been widely studied, a quantitative comparison would facilitate a better understanding of the kinetic and physical impact of the EB initiation mechanism, which is substantially more difficult to characterize. Here, a protocol was developed that enables investigation of EB and photopolymerized films of equivalent initiation energies. Using this protocol, the impact of the initiation mechanism on energy rate effects (EREs) was characterized for a series of five acrylate monomers. Differences in polymer conversion and physical properties were determined via Raman spectroscopy and dynamic mechanical analysis, respectively. In comparison to the EB-polymerized films of equivalent initiation energy and energy rate, the photopolymerized films had equal or lower conversions. Additionally, monomer chemistry was a key factor for differentiating ERE magnitude across the five-monomer series for both initiation mechanisms. Differences between initiation mechanisms were also demonstrated in Tg, FWHM of the tan δ peak, and the maximum tan δ peak height for two of the monomer formulations. Quantifying these differences not only improves knowledge of fundamental kinetics, but also provides a foundation for predictive chemical structure/processing parameter/polymer property relationships.

Новейшие разработки моделей и расчётных схем для количественного анализа физических свойств полимеров

Новейшие разработки моделей и расчётных схем для количественного анализа физических свойств полимеров

Influence of printing parameters on the stability of deposited beads in fused filament fabrication of poly(lactic) acid

Fused filament fabrication (FFF) is one of the various types of additive manufacturing processes. Similar to other types, FFF enables free-form fabrication and optimised structures by using polymeric filaments as the raw material. This work aims to optimise the printing conditions of the FFF process based on reliable properties, such as printing parameters and physical properties of polymers. The selected polymer is poly(lactic) acid (PLA), which is a biodegradable thermoplastic polyester derived from corn starch and is one of the most common polymers in the FFF process. Firstly, the maximum inlet velocity of the filament in the liquefier was empirically determined according to process parameters, such as feed rate, nozzle diameter and dimensions of the deposited segment. Secondly, the rheological behaviour of the PLA, including the velocity field, shear rate and viscosity distribution in the nozzle, was determined via analytical study and numerical simulation. Our results indicated the variation in the shear rate according to the diameter of the nozzle and the inlet velocity. The shear rate attained its maximum value near the internal wall at high inlet velocities and smaller diameters. Finally, the distribution of the viscosity along the radius of the nozzle was obtained. At high inlet velocity, several defects appeared at the surface of the extrudates. At the highest shear rates, the extrudates underwent severe deformation. The defects predicted via numerical simulation were reasonably consistent with that observed from an optical microscope. Hence, these results are effective for selecting the printing parameters (i.e. nozzle diameter, feed rate and layer height) to improve the quality of the manufactured parts.

A Genetically Encoded Protein Polymer for Uranyl Binding and Extraction Based on the SpyTag-SpyCatcher Chemistry.

A defining goal of synthetic biology is to develop biomaterials with superior performance and versatility. Here we introduce a purely genetically encoded and self-assembling biopolymer based on the SpyTag-SpyCatcher chemistry. We show the application of this polymer for highly efficient uranyl binding and extraction from aqueous solutions, by embedding two functional modules-the superuranyl binding protein and the monomeric streptavidin-to the polymer via genetic fusion. We further provide a modeling strategy for predicting the polymer's physical properties, and experimentally demonstrate the autosecretion of component monomers from bacterial cells. The potential of multifunctionalization, in conjunction with the genetic design and production pipeline, underscores the advantage of the SpyTag-SpyCatcher biopolymers for applications beyond trace metal enrichment and environmental remediation.

Synthesis of urea‐containing ABA triblock copolymers: Influence of pendant hydrogen bonding on morphology and thermomechanical properties

ABSTRACTReversible addition‐fragmentation chain transfer (RAFT) polymerization produced novel ABA triblock copolymers with associative urea sites within pendant groups in the external hard blocks. The ABA triblock copolymers served as models to study the influence of pendant hydrogen bonding on polymer physical properties and morphology. The triblock copolymers consisted of a soft central block of poly(di(ethylene glycol) methyl ether methacrylate) (polyDEGMEMA, 58 kg/mol) and hard copolymer external blocks of poly(2‐(3‐hexylureido)ethyl methacrylate‐co‐2‐(3‐phenylureido)ethyl methacrylate) (polyUrMA, 18‐116 kg/mol). Copolymerization of 2‐(3‐hexylureido)ethyl methacrylate (HUrMA) and 2‐(3‐phenylureido)ethyl methacrylate (PhUrMA) imparted tunable hard block Tg's from 69 to 134 °C. Tunable hard block Tg's afforded versatile thermomechanical properties for diverse applications. Dynamic mechanical analysis (DMA) of the triblock copolymers exhibited high modulus plateau regions (∼100 MPa) over a wide temperature range (−10 to 90 °C), which was indicative of microphase separation. Atomic force microscopy (AFM) confirmed surface microphase separation with various morphologies. Variable temperature FTIR (VT‐FTIR) revealed the presence of both monodentate and bidentate hydrogen bonding, and pendant hydrogen bonding remained as an ordered structure to higher than expected temperatures. This study presents a fundamental understanding of the influence of hydrogen bonding on polymer physical properties and reveals the response of pendant urea hydrogen bonding as a function of temperature as compared to main chain polyureas. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 1844–1852

Fabrication of hybrid gel nanofibrous polymer electrolyte for lithium ion battery

Fibrous membranes are promising separators for high-performance lithium ion battery because of their high porosity and superior electrolyte uptake. In this paper, the fabrication of hybrid gel polymer electrolyte (HGPE) by introducing SnO2 nanoparticles in poly(vinylidine fluoride) by electrospinning technique and soaking the electrospun nanofibrous membranes in 1 M LiPF6 in ethylene carbonate (EC)/diethyl carbonate (DEC) (1:1, v/v). The as-prepared electrospun HGPE with SnO2 nanofiller was characterized by scanning electron microscopy. The influence of SnO2 on the structure of polymer membrane, physical, and electrochemical properties is systematically investigated. HGPE shows significant high ionic conductivity 4.6 × 10[Formula: see text] S/cm at room-temperature and better cell performance such as discharge C-rate capability and cycle performance. The hybrid gel polymer nanofibrous membrane favors high uptake of lithium electrolyte so that electrolyte leakage is reduced. The gel polymer electrolyte with SnO2 filler was used for the fabrication of Li/PVdF-SnO2/LiFePO4 coin cell. The fabricated cell was evaluated at a current density of 0.2 C-rate and delivered stable and excellent cycle performance. This study revealed that the prepared HGPE can be employed as potential electrolyte for lithium ion batteries.

Aerosol Assisted Dielectric Barrier Discharge Plasma Jet for PMMA/ZnS Nanocomposite Thin Films Preparation

Pure Poly methyl methacrylate (PMMA) thin films and PMMA mixed with 1 %, 3%, 5% &amp;7% by weight of ZnS nanoparticles (NP) were prepared by plasma jet technique. Formulation of the polymer with nanoparticles allows for modification of polymer physical properties. The PMMA /ZnS nanocomposite prepared by polymerization in plasma jet and characterized by Ultra Violet Visible UV-Vis, Fourier Transform Infra-Red Spectrophotometer (FTIR), Atomic Force Microscopy (AFM) and SEM to study the effect of ZnS nanoparticles on the optical properties, morphology and structure of the thin films. The FTIR spectra for the films show an interaction between PMMA and NPs. There is a decrease in the optical band gap of films prepared with an increase of the concentration of NPs. AFM and SEM images show that there are a few clusters of ZnS and there is a homogeneous distribution of the nanoparticles in the PMMA matrix.

An Inversion Method of Relative Permeability Curves in Polymer Flooding Considering Physical Properties of Polymer

Summary Reliable relative permeability curves of polymer flooding are of great importance to the history matching, production prediction, and design of the injection and production plan. Currently, the relative permeability curves of polymer flooding are obtained mainly by the steady-state, nonsteady-state, and pore-network methods. However, the steady-state method is extremely time-consuming and sometimes produces huge errors, while the nonsteady-state method suffers from its excessive assumptions and is incapable of capturing the effects of diffusion and adsorption. As for the pore-network method, its scale is very small, which leads to great size differences with the real core sample or the field. In this paper, an inversion method of relative permeability curves in polymer flooding is proposed by combining the polymer-flooding numerical-simulation model and the Levenberg-Marquardt (LM) algorithm. Because the polymer-flooding numerical-simulation model by far offers the most-complete characterization of the flowing mechanisms of polymer, the proposed method is able to capture the effects of polymer viscosity, residual resistance, diffusion, and adsorption on the relative permeability. The inversion method was then validated and applied to calculate the relative permeability curve from the experimental data of polymer flooding. Finally, the effects of the influencing factors on the inversion error were analyzed, through which the inversion-error-prediction model of the relative permeability curve was built by means of multivariable nonlinear regression. The results show that the water relative permeability in polymer flooding is still far less than that in waterflooding, although the residual resistance of the polymer has been considered in the numerical-simulation model. Moreover, the accuracy of the polymer parameters has great effect on that of the inversed relative permeability curve, and errors do occur in the inversed water relative permeability curve—the measurements of the polymer solution viscosity, residual resistance factor, inaccessible pore-volume (PV) fraction, or maximum adsorption concentration have errors.

Newest models and calculation schemes for quantitative analysis of physical properties of polymers

New models and calculation schemes have been developed for the quantitative analysis of a number of physical properties of polymers — glass transition temperature, flow temperature of polymer nanocomposites, thermal conductivity, boiling point of polymer solutions, water absorption and water permeability of polymers and nanocomposites, strength, viscosity, storage and losses moduli, refractive index and dielectric constant. All calculation schemes are based on the structure of linear and cross-linked polymers; their degree of crystallinity, free volume, the effect of temperature, the composition of copolymers and homogeneous mixtures of polymers, the concentration of nanoparticles, their shape, size distribution, orientation angles, the structure of polar groups grafted to the surface of nanoparticles, the energy of intermolecular interactions are taken into account. All computational schemes are computerized and allow calculations to be carried out automatically after the introduction of the structure of a repeating unit of polymer unit into the computer, as well as the shape and size of nanofillers.

Design, Synthesis, and Self-Assembly of Polymers with Tailored Graft Distributions.

Grafting density and graft distribution impact the chain dimensions and physical properties of polymers. However, achieving precise control over these structural parameters presents long-standing synthetic challenges. In this report, we introduce a versatile strategy to synthesize polymers with tailored architectures via grafting-through ring-opening metathesis polymerization (ROMP). One-pot copolymerization of an ω-norbornenyl macromonomer and a discrete norbornenyl comonomer (diluent) provides opportunities to control the backbone sequence and therefore the side chain distribution. Toward sequence control, the homopolymerization kinetics of 23 diluents were studied, representing diverse variations in the stereochemistry, anchor groups, and substituents. These modifications tuned the homopolymerization rate constants over 2 orders of magnitude (0.36 M-1 s-1 < khomo < 82 M-1 s-1). Rate trends were identified and elucidated by complementary mechanistic and density functional theory (DFT) studies. Building on this foundation, complex architectures were achieved through copolymerizations of selected diluents with a poly(d,l-lactide) (PLA), polydimethylsiloxane (PDMS), or polystyrene (PS) macromonomer. The cross-propagation rate constants were obtained by nonlinear least-squares fitting of the instantaneous comonomer concentrations according to the Mayo-Lewis terminal model. In-depth kinetic analyses indicate a wide range of accessible macromonomer/diluent reactivity ratios (0.08 < r1/r2 < 20), corresponding to blocky, gradient, or random backbone sequences. We further demonstrated the versatility of this copolymerization approach by synthesizing AB graft diblock polymers with tapered, uniform, and inverse-tapered molecular "shapes." Small-angle X-ray scattering analysis of the self-assembled structures illustrates effects of the graft distribution on the domain spacing and backbone conformation. Collectively, the insights provided herein into the ROMP mechanism, monomer design, and homo- and copolymerization rate trends offer a general strategy for the design and synthesis of graft polymers with arbitrary architectures. Controlled copolymerization therefore expands the parameter space for molecular and materials design.

Poly(glycerol adipate) – indomethacin drug conjugates – synthesis and in vitro characterization

The linear biodegradable polyester poly(glycerol adipate) (PGA) was synthesized via enzymatic polycondensation using lipase B from Candida antarctica (CAL-B). Every monomer unit of PGA possesses a pendant hydroxyl group which is responsible for the hydrophilic character and moisture swelling. These OH groups were esterified to different degrees with the anti-inflammatory drug indomethacin in order to create a prodrug with a pH-sensitive linker for modified drug release. The structure of the conjugates was determined via ATR FT-IR spectroscopy, NMR spectroscopy, GPC and UV/VIS spectroscopy. The physical properties of polymers with different drug load were investigated using DSC, contact angle measurements and oscillatory rheology. Drug release was monitored over one month in vitro. A very slow, but continuous release was observed in PBS. Slightly acidic conditions and lipase activity are accelerating the indomethacin release. Therefore, poly(glycerol adipate) − indomethacin conjugates are promising prodrugs for the local sustained release of indomethacin.

Topological effects of macrocyclic polymers: from precise synthesis to biomedical applications

Polymer chain architectures play a crucial role in the physical properties of polymers and this unique phenomenon has been recognized as the topological effects. As one of the most representative architectures, macrocyclic polymers characterized by the endless topology have received extensive attention due to their distinct physical properties as compared to the linear counterparts. To understand these differences and unravel the underlying mechanisms, there is a long pursuit to efficiently fabricate macrocyclic polymers. To date, both ring-closing and ring-expansion strategies have been developed, which drastically elevates the accessibility of macrocyclic polymers. The improved availability of macrocyclic polymers enables the further investigation of the biomedical applications and the preliminary results suggest that macrocyclic polymers outperform their linear analogs in terms of improving gene delivery efficiency, elevating blood circulation time, and enhancing colloidal stability of nanoparticles.

Influence of fluorination on barrier properties of polymers: Insights from Monte Carlo simulations of eicosanes + methane.

Fluorination is widely used to improve the resistance and physical properties of polymers that are cheap to manufacture. This process improves the resistance properties of unfluorinated materials. This study examines the effects of varying the degree of fluorination on the clustering and absorption behaviour of methane n-eicosane. Monte Carlo simulations were performed for several different pressure values, at ambient temperature, to determine the uptake of methane into the eicosanes. The density of the pure eicosanes, simulated at ambient conditions, compared favourably with experimental data for the relevant polymers. The spatial configurations resulting from the absorption simulations were analysed to determine the clustering behaviour of absorbed methane. Both the prevalence of cluster formation in general, and the occurrence of specific cluster topologies of various sizes were considered. Cyclic clusters had a tendency to become more prevalent in unfluorinated eicosanes as the gas pressure was increased, while the presence of fluorine atoms on the eicosane backbone appeared to inhibit the formation of such clusters.

Utilisation of agro-waste extract in thermoplastics

Functionally active polymers were created through the incorporation of an extract from an agro-waste stream from the wine industry. Incorporation of this extract into three thermoplastics shows its potential to increase antioxidant activity, with minimal to no impact on the mechanical attributes of the polymers. Antioxidant activity was shown to be effective at a concentration of 1%(w/w) grape tannin in polypropylene and linear low-density polyethylene (LLDPE). The ability to obtain antioxidant activity at low concentrations helps minimise costs and maintain polymer physical properties. The binding of the phenolic compounds results in low leachability, thereby ensuring that the active compounds remain in the polymer for greater long-term effectiveness.

Photophysical and thermal properties of polyazomethines containing various flexible units

In this study, the poly(azomethine-ether-urethane), poly(azomethine-ester) and poly(azomethine-epoxyether) compounds were prepared to investigate effect of various flexible units on some physical properties like thermal stability and photophysical properties. Structural characterizations were made by FTIR, 1H NMR, 13C NMR, and UV-Vis analyses. The molecular weight distributions of polymers were performed by gel permeation chromatography (GPC) measurement. The chemical and physical properties of polymers were examined by thermogravimetry (TG), differential scanning calorimetry (DSC), photoluminescence (PL), dynamic mechanical analysis (DMA), scanning electron microscope (SEM) and atomic force microscopy (AFM) techniques. As a result, the outstanding properties related to the photoluminescence and thermal measurements of the polymers were obtained. Therefore, the presented photoluminescent polymers could be used in thermally stable photo-functional materials.

Influence of RAFT end‐groups on the water swelling of poly( N ‐propyl methacrylate)

The immersion of poly(n-propyl methacrylate), PPMA, films (ca., 425 nm) in water induces swelling that is measured in-situ using spectroscopic ellipsometry. Unexpectedly, the end group of the PPMA resulting from the reversible addition-fragmentation chain transfer (RAFT) polymerization impacts the temperature dependence of swelling, despite their relatively high molecular weights (ca., 30 kDa). At 25 °C, dithiobenzoate terminated PPMA (PPMA-DB) leads to significantly less swelling (5.6 vol %) than the dodecylsulfanylthiocarbonyl terminated PPMA (PPMA-DD, 9.0 vol %). These PPMA films swell significantly more than expected due to a common carboxylic acid end group. As temperature is increased, the swelling for PPMA-DB increases and that for PPMA-DD decreases, with a crossover at approximately 35 °C–40 °C where the swelling is indistinguishable between the two polymers. The swelling kinetics exhibit two stages: an initial rapid swelling within the first minute of immersion and then a slow increase in thickness over multiple hours. The water contact angle of PPMA-DB increases on heating, while the water contact angle of PPMA-DD is invariant. This difference in the temperature dependence of the hydrophobicity is consistent with that for swelling. These results illustrate the potential unexpected consequences of residual RAFT fragment end groups on physical properties of polymers even at relatively high molecular weights. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 77–84

Influence of dimethyl sulfoxide used as a solvent on the physical properties and long-term dentin bonding of hydrophilic resins

ObjectiveTo examine the feasibility of dimethyl sulfoxide (DMSO) incorporation into relatively hydrophilic resins as a new potential method to improve the durability of resin–dentin bonds. MethodsSix experimental light-curing BisGMA/HEMA resins solvated in ethanol and DMSO with increasing concentrations of DMSO (0, 0.5, 1, 2, 4 and 10wt%) were prepared. The degree of conversion (DC) was evaluated by Fourier Transform Infrared Spectroscopy (n=8); water sorption (Wsp) and water solubility (Wso) were gravimetrically assessed (n=10); and flexural strength (FS) and elastic modulus (E) were determined by a three-point bending flexural test (n=10). Flat dentin surfaces on sound third molars (n=10/group) were bonded with resins containing 0, 2, 4 and 10wt% DMSO used as a two-step etch-and-rinse system. Dentin microtensile bond strength was determined at 24h and after two-year aging in artificial saliva at 37°C. ResultsDMSO significantly affected Wsp (p=0.0006), DC, Wso, FS, and E (p<0.0001). In general, the resins’ mechanical/physical properties were not affected by 2% or lower DMSO incorporation. Incorporation of 4% or higher DMSO content significantly increased DC, Wsp and Wso, but 2% or higher DMSO concentrations significantly reduced FS and E. No influence on immediate dentin bond strength occurred up to 4% DMSO incorporation. While 4% or higher DMSO concentrations impaired bond strength over time, the resin containing 2% DMSO presented significant higher dentin bond strength compared to the control resin after two year-aging. SignificanceThe use of DMSO as a new solvent in adhesive dentistry improves dentin bonding of relatively hydrophilic resins over time. 2% DMSO incorporation in BisGMA/HEMA resins should be sufficient to reduce bond strength loss without compromising polymer mechanical strength and physical properties.

One-step synthesis, biodegradation and biocompatibility of polyesters based on the metabolic synthon, dihydroxyacetone

The one-step synthesis of a polyester family containing dihydroxyacetone is described along with a quantitative analysis of in vitro/in vivo degradation kinetics and initial biocompatibility. Polyesters were synthesized by combining dihydroxyacetone, which is a diol found in the eukaryotic glucose metabolic pathway, with even-carbon aliphatic diacids (adipic, suberic, sebacic) represented in the long-chain alpha carboxylic acid metabolic pathway, by Schӧtten-Baumann acylation. We show that by using a crystalline monomeric form of dihydroxyacetone, well-defined polyesters can be formed in one step without protection and deprotection strategies. Both diacid length and polyester molecular weight were varied to influence polymer physical and thermal properties. Polyesters were generated with number-averaged (Mn) molecular weights ranging from 2200–11,500. Polydispersities were consistent with step-growth polymerization and ranged from 2 to 2.6. The melting (Tm) and recrystallization (Tc) temperatures were impacted in an unpredictable manner. Thermal transitions for the polyesters were highest for the adipic acid followed by suberic acid and sebacic acid, respectively. It was shown that the thermal response of the DHA-based polyesters was influenced by both the diacid length and molecular weight. In vitro degradation studies revealed first-order weight loss kinetics, the molecular weight loss followed first order kinetics with 25%–40% of the original mass remaining after 8 weeks. In vivo testing over 16 weeks highlighted that mass loss ranged from ∼70% to ∼6% depending upon initial molecular weight and diacid length. Histological analysis revealed rapid resolution of both acute and chronic inflammatory responses, normal foreign body responses were observed and no inflammation was present after week 4. This one-step synthesis proved robust with unique copolymers warranting further study as potential biomaterials.