Hydration of phosphorylcholine groups attached to highly swollen polymer hydrogels studied by thermal analysis

Hydration of polymer chains plays a key role for determining the extent of protein adsorption on polymeric materials. Here we investigated the hydration of poly(2-methacryloyloxyethyl phosphorylcholine (MPC)) chains, which resist protein adsorption and following cell adhesion effectively. The hydration was compared with that of poly(methoxy oligo(ethylene glycol)-monomethacrylate (Me(EG)_nMA)) chains, which also have hydrophilic units. The poly(MPC) and poly(Me(EG)_nMA) hydrogels with equilibrium water contents (EWCs) in the range from 86 to 97 wt% were prepared. By differential scanning calorimetric measurements, water in both the hydrogels was classified into two states: freezable and nonfreezable water. The poly(MPC) hydrogels had larger nonfreezable water than the poly(Me(EG)_nMA) hydrogels even when their EWCs were similar, which indicated the higher hydrating ability of poly(MPC) chains. We suggested that the difference in the amount of nonfreezable water around polymer chains may influence the degree of protein adsorption resistance after contact with body fluid for a long period.     

Effect of propyleneimine external cross-linker on the properties of acrylate latex pressure sensitive adhesives

Acrylate pressure sensitive adhesive (PSA) latexes were synthesized via a starved monomer seeded semi-batch emulsion polymerization process with butyl acrylate (BA), methyl methacrylate (MMA), acrylic acid (AA) and 2-hydroxyethyl acrylate (HEA). These PSA polymers were then cross-linked with trifunctional propyleneimine external cross-linker (SAC-100) to study the cross-linking reaction between carboxylic group of the polymer chain and cross-linking agent. It was found that cross-linking provided a significant influence on the film formation process based on the result of SEM analysis. In addition, with the increase of SAC-100 content, the gel content of the polymer increased significantly, while molecular weight between cross-link points (M_c) and the sol molecular weight (M_w, M_n) of the polymer decreased remarkably. The TGA result showed that the addition of the external cross-linker can enhance the thermal stability of the latex film. Moreover, for the cross-linked adhesive film, the shear strength was improved greatly while at the sacrifice of loop tack and peel strength, when compared with the uncross-linked counterparts. Besides, dynamic mechanical analysis (DMA) was also used to evaluate the viscoelastic properties of the acrylate emulsion PSA film.     

Curing behavior,mechanical properties,intermolecular interaction,and morphology of silicone/polypyrrole/polymer electrolyte composites

The curing behavior, mechanical properties, intermolecular interaction, and morphology of silicone, polypyrrole, and polymer electrolyte composites were studied. A rigid‐body pendulum rheometer was used to determine the curing behavior of silicone/PEL blends. The polymer structure was evaluated using FTIR and Differential Scanning Calorimetery. The mechanical properties, including stress, strain, and hardness, were measured using a material testing system. The morphology of the composites was measured using scanning electron micrographs. The intermolecular interaction of the composites was measurement using dynamic mechanical analysis. The results show that the curing reaction rate is fast upon addition of 10 wt % of polymer electrolyte for silicone. The linear molecular structure of the polymer electrolyte was wound around the silicone polymer network structure forming a semi‐interpenetrating network. The intermolecular interaction was influenced by the composites, and the Ppy film effect on the surface of SP10 blends is more uniform than that of silicone. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2754–2764, 2006     

Study on a new polymer/graphene oxide/clay double network hydrogel with improved response rate and mechanical properties

pH‐ and temperature‐responsive double network hydrogels (DN hydrogels) were prepared by using poly (N‐isopropylacrylamide) (PNIPAM) as a tightly crosslinked network (1st network), polyacrylic acid (PAA) as a loosely crosslinked network (2nd network), with clay and graphene oxide as effective crosslinkers and reinforcing fillers. The structure and morphology of the hydrogels were characterized by SEM, FTIR, DSC, and TGA. The synergetic effects of clay, GO and DN structure on various physical properties were investigated. With the increasing of crosslinking densities, the swelling ratios of DN hydrogels gradually decreased by increasing the contents of graphene oxide and PAA. While the DN hydrogels had much better mechanical properties than that of the conventional chemically cross‐linked PNIPAM hydrogels. POLYM. ENG. SCI., 55:1361–1366, 2015. © 2015 Society of Plastics Engineers     

互穿网络敏感型聚氨酯水凝胶的合成与研究

以异佛尔酮二异氰酸酯（IPDI）、聚氧化丙烯二醇（PPG-220）、二羟甲基丙酸（DMPA）、蓖麻油（C0）等为主要原料,合成交联型水性聚氨酯乳液,在此乳液中加入丙烯酰胺、引发剂（KPS）,交联剂（BMA）进行自由基聚合,制备具有IPN结构的聚氨酯-聚丙烯酰胺（PU—PAAm）水凝胶。研究了（PU—PAAm）水凝胶溶胀率（SR）受pH值、温度（T）、交联剂用量等因素的影响。     

聚合物材料力学性能的计算机模拟

聚合物材料的宏观力学性能与其微观结构具有密切的关系,计算机模拟是研究这种结构与性能关系的重要手段之一,近年来国内外学者已经发展了多种模拟方法并从不同尺度来模拟聚合物材料的力学性能。本文综述了不同方法在聚合物材料力学性能模拟研究中的应用,重点介绍了Monte Carlo模拟、分子动力学模拟和基于弹簧格子模型的多尺度模拟这3种常见模拟方法的应用情况,如在分子动力学模拟中重点关注无定形聚合物玻璃态、结晶聚乙烯和部分非均质体系,而在多尺度模拟中则重点关注复杂的非均质聚合物体系,并讨论了各种方法的应用前景及亟待解决的问题。     

Synthesis,characterization, mechanical properties and biocompatibility of interpenetrating polymer network–super‐porous hydrogel containing sodium alginate

In this investigation an interpenetrating polymer network–superporous hydrogel containing sodium alginate (IPN‐SPH_Alg) was synthesized. The morphology of the polymer was characterized using scanning electron microscopy, light images and porosity, and the polymer was further examined by swelling ratio, mechanical strength and biocompatibility. The results indicated that the IPN‐SPH_Alg possessed both large numbers of interconnected pores and an interpenetrating network. The swelling ratio of IPN‐SPH_Alg was lower than that of the superporous hydrogel (SPH) and it decreased as the sodium alginate/monomer ratio increased. The IPN‐SPH_Alg exhibited pH responsiveness and salt‐sensitive properties. Compared to SPH and SPH composites, the mechanical strength of IPN‐SPH_Alg was significantly enhanced. Thiazolyl blue assay on AD293 cells, in situ lactate dehydrogenase assay and morphological study of rat intestine showed that the polymer induced no significant cell or mucosal damage. The fast swelling, good mechanical properties, pH sensitivity and biocompatibility of the IPN‐SPH_Alg suggested it as a potential candidate in the field of drug‐delivery systems. Copyright © 2007 Society of Chemical Industry     

Morphological structure and mechanical properties of polyurethane modified with methyl methacrylate

Three kinds of polyurethane-poly(methyl methacrylate) (PU–PMMA), that is, linear polymer, block copolymer, and interpenetrating polymer network (IPN), were synthesized by a simultaneous polymerization process, respectively. The effects of several factors such as ultraviolet (UV) setting, heat setting, chemical composition, and physical structure on the morphological structure and mechanical properties of polymers were studied by scanning electron micrograph, dynamic mechanical loss spectrum, and mechanical tests. The results show that PU–PMMA is a partially compatible system with a two-phase structure; the linear polymer has the highest elongation at break, and IPN has the strongest tensile strength, while the block copolymer has poor mechanical properties. In addition, the UV setting block copolymer and IPN system, with regular microphase domain structures, have higher tensile strength and elongation at break than those of heat setting polymers. With MMA content and hard segment in PU increasing, the tensile strength increases, and the elongation decreases. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1363–1369, 1998     

Tensile and dynamic mechanical properties of improved ultrathin polymeric films

Tensile and dynamic mechanical properties of improved ultrathin polymeric films for magnetic tapes are presented. These films include poly(ethylene terephthalate) or PET, poly(ethylene naphthalate) or PEN, and aromatic polyamide (ARAMID). PET film is currently the standard substrate used for magnetic tapes; thinner tensilized‐type PET, PEN, and ARAMID were recently used as alternate substrates with improved material properties. The thickness of the films ranges from 6.2 to 4.8 μm. Young's modulus of elasticity, F5 value, strain‐at‐yield, breaking strength, and strain‐at‐break were obtained at low strain rates by using a tensile machine. Storage (or elastic) modulus, E′, and the loss tangent, tan δ, which is a measurement of viscous energy dissipation, are measured by using a dynamic mechanical analyzer at temperature ranges of ?50 to 150°C (for PET), and ?50 to 210°C (for PEN and ARAMID), and at a frequency range of 0.016 to 29 Hz. Frequency–temperature superposition was used to predict the dynamic mechanical behavior of the films over a 28 decade frequency range. Results show that ARAMID and tensilized films tend to have higher strength and moduli than standard PET and PEN. The rates of decrease of storage modulus as a function of temperature are lower for PET films than those for PEN and ARAMID films. Storage modulus for PEN films are higher than that for PET films at high frequencies, but this relationship reverses at low frequencies. ARAMID has the highest modulus and strength among the films in this study. The relationship between polymeric structure and mechanical properties are also discussed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2225–2244, 2002     

温度、pH及离子强度敏感性聚氨酯水凝胶的合成与性能研究

以甲苯二异氰酸酯(TDI)、聚乙二醇(PEG-6000)、二羟甲基丙酸(DMPA)及三乙撑四胺(TEFA)等为原料,合成了温度、pH、及离子强度敏感性聚氨酯水凝胶(PUHG)。研究了PUHG溶胀率(SR)受温度(T)、pH、离子强度(I)、交联剂用量等因素的影响。结果表明PUHG的溶胀率在20~45℃的范围内随温度的升高而减小,45℃后不再变化;在酸性(pH4)溶液中收缩,在碱性(pH9)溶液中溶胀,表现出良好的pH值敏感性;在一定温度和pH下,随着离子强度的增加PUHG的溶胀率减小。水凝胶溶胀动力学研究表明,PUHG具有良好的溶胀-退胀可逆性。     

Synthesis and mechanical properties of leather–epoxy interpenetrating polymer networks

Leather–epoxy interpenetrating polymer networks (IPNs) were synthesized; these IPNs have an approximate epoxy concentration of 25 wt %. The flexural and tensile moduli of the IPNs prepared are equivalent to those of the epoxy resin. The Izod impact energy and fracture toughness measured for the IPNs, however, exceed those attained by the epoxy resin alone by at least a factor of 4. The glass transition of leather–epoxy IPNs occurs over a wide temperature range, thus indicating that the IPN is an intimate admixture of the epoxy resin throughout the collagen matrix of the hide. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1224–1232, 2000     

Relationship between the morphological structure and mechanical properties of copper‐in‐hydrophilic polymer gradient composite films

This investigation was focused on the influence of polymer hydrophilicity on the morphological structure and mechanical properties of copper‐in‐polymer gradient composite films (CPGCFs). The ion motion and reduction in swelling cathode films under an electric field were the core of the gradient morphology formation of a metal region in the polymer matrix. The morphological study of CPGCFs revealed that the hydrophilicity of poly(vinyl alcohol) was helpful in forming a continuously deposited layer. The nanoclusters (40 nm) aligned into a branchlike form in the copper‐rich region in the poly(vinyl alcohol) matrix. On the basis of the fuzzy interface between the poly(vinyl alcohol) matrix and copper nanoclusters, a complex interaction between them was inferred. The reduced copper affected the mechanical properties of CPGCFs. The maximum load of CPGCFs could be enhanced by 25% to 167.0 N with optimal electrochemical reduction, but the elongation was depressed. An excess of reduced copper in the polymer matrix reduced both the strength and elongation of CPGCFs. The moduli of related samples showed trends similar to those of the strength. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 539–545, 2005     

EA/St-AN互穿聚合物网络的加工和力学性能

以丙烯酸乙酯为软单体 ,苯乙烯和丙烯腈为硬单体 ,二乙烯基苯或三乙二醇双丙烯酸酯为交联剂 ,采用多步种子乳液聚合技术制备了半互穿和全互穿聚合物网络 ,研究了软、硬单体配比 ,交联剂用量 ,加工次数对共聚物流变行为、力学性能和结构形态的影响。结果表明 ,制备的半互穿和全互穿聚合物网络均可在适宜的条件下流动成型。如果配方选择适当 ,反复加工后力学性能基本不变     

Morphology and mechanical properties of semi-interpenetrating polymer networks from polyurethane and benzyl konjac glucomannan

A series of semi-interpenetrating polymer network (semi-IPN) films coded as UB from castor oil-based polyurethane (PU) and benzyl konjac glucomannan (B-KGM) were prepared, and they have good or certain miscibility over entire composition range. Morphology, miscibility and properties of the UB films were investigated by using scanning electron microscopy (SEM), differential scanning calorimetry, dynamic mechanical analysis, ultraviolet spectrometer, wide-angle X-ray diffraction and tensile test. The results indicated that the UB films exhibited good miscibility when B-KGM content was lower than 15 wt%, resulting in relatively high light transmittance, breaking elongation and density. With an increase of the B-KGM content from 20 to 80 wt%, a certain degree of phase separation between PU and B-KGM occurred in the UB films. The tensile strength of the films UB increased from 7 to 45 MPa with an increase of B-KGM content from 0 to 80 wt%. By extracting the B-KGM with N, N-dimethylformamide from the semi-IPN, the morphology and phase domain size of the UB films were clearly observed by SEM. A continuous phase and dual-continuous phase model describing the semi-IPN were proposed to illustrate the morphology and its transition.     

Structural, mechanical and osmotic properties of injectable hyaluronan-based composite hydrogels

The osmotic and scattering properties of hyaluronan-based composite hydrogels composed of stiff biopolymer chains (carboxymethylated thiolated hyaluronan (CMHA-S)) crosslinked by a flexible polymer (polyethylene glycol diacrylate (PEGDA)) are investigated and analyzed in terms of the scaling theory. The total pre-gel polymer weight concentration is varied between 0.5 wt.% and 3.2 wt.%, while the mole ratio between the reactive PEG chain ends and the thiolated HA moieties is changed between 0.15 and 1.0. The shear modulus G of the fully-swollen gels exhibits a stronger dependence on pre-gel concentration than on the crosslink density. Osmotic deswelling measurements reveal that the osmotic mixing pressure depends on the weight ratio CMHA-S/PEGDA, and is practically unaffected by the pre-gel concentration. Small-angle neutron scattering observations indicate that the thermodynamic properties of these composite gels are governed by total polymer concentration, i.e., specific interactions between the two polymeric components do not play a significant role.     

Computer simulation of phase structure and mechanical properties of polymer mixtures

Computer programs have been developed to predict phase separation, flow-induced phase structure, and structure-dependent mechanical properties of binary polymer mixtures. The phase separation is simulated by solving a two-dimensional Langevin equation with Flory–Huggins free energy using the finite difference method under periodic boundary conditions. The change of phase structure due to flow is predicted by adding a shear flow term to the equation. By generating a finite element mesh from the calculated phase structure, the stress analysis is carried out for estimating the mechanical properties of the system using the finite element method. The elastic modulus and thermal expansion coefficient based on the phase structure were numerically investigated for various volume fractions and properties of components using the developed programs. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68:807–813, 1998     

Development of techniques to compare mechanical properties of reversible hydrogels with spherical, square columnar and ocular lens geometry

We have developed a new experimental technique for determining the elastic modulus of the ocular lens by using hydrogel phantoms. We successfully prepared disulfide-reversible polyacrylamide hydrogels in the forms of a square column, a sphere, and a lens. The M_n (number average molecular weight) of the reduced copolymer ranged from 696,800 to 870,900 Da. The physical and swelling properties of the gels were independent of shape. The M_c (molecular weight between cross-links) ranged from 1776 to 1887 compared with the theoretical M_c of 1638 Da. The gels exhibited non-linear rubber elasticity, but at low strains the elastic moduli (E) were 4680±150, 5010±280, and 4870±220 Pa for the square column, sphere, and lens, respectively. The shear modulus (G) was 1531±70 Pa with an E/G ratio of approximately 3:1, indicating an incompressible gel at low strains. At high strains (∼15%) the Mooney-Rivlin plot was linear and the magnitude of 2C₁ was 1515 Pa, which was comparable to the shear modulus of the gels. Finally, the Tatara mechanical model for large deformation of rubber spheres was successfully applied to extract the elastic modulus of the lens. The modulus of the lens obtained with this technique was consistent with the moduli for the square column and sphere. The new technique will be used to determine the mechanical properties of the ocular lens.     

Phase transitions and mechanical properties of nitrocellulose plasticized by glycidyl azide polymer and nitroglycerine

Films of nitrocellulose (NC), glycidyl azide polymer (GAP), and nitroglycerine (NG) have been evaluated using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, dynamic mechanical analysis (DMA), and tensile testing. The SEM micrographs demonstrate that, even at low GAP concentration, a portion of GAP will coalesce into spherical domains due to a saturation effect. This is related to the inability of higher molecular weight GAP to effectively situate itself between NC polymer chains. The addition of a small fraction of lower molecular weight NG completely changes this behavior. DMA confirms that two transitions are present and can be attributed to a plasticizer rich phase (β), a polymer rich phase (α) and that NC plasticized with GAP is in accordance with the Gordon-Taylor equation. Tensile results show that the addition of a small fraction of NG to a NC/GAP based-formulation increases elongation at break to values similar to that of the NC/NG base formulation. The combination of these two plasticizers, GAP and NG, allows for the plasticization of NC at significantly lower environmental and human toxicity levels.     

Molecular design of reactive amphiphilic phospholipid polymer for bioconjugation with an enzyme

Water‐soluble amphiphilic phospholipid random copolymers such as poly(2‐methacryloyloxyethyl phosphorylcholine (MPC)‐random‐n‐butyl methacrylate (BMA)) and block‐type polymer, poly(MPC‐block‐BMA) (Mw = 1.0 × 10⁴) with a carboxylic group on a terminal, were designed by photoinduced living radical polymerization. These polymers and poly(MPC) were conjugated to an enzyme, papain. The effects of BMA units in the polymers on the enzymatic activity and stability were investigated. The modification degrees of papain with poly(MPC‐random‐BMA) and poly(MPC‐block‐BMA) were 16–19% versus the total number of amino groups in native papain. The remaining α‐helix content of papains conjugated with poly(MPC‐random‐BMA) and poly(MPC‐block‐BMA) was maintained, but the remaining activity of the papains decreased with an increase in the composition of BMA units in the polymers. These activities were small compared to the papain conjugated to poly(MPC). However, the papains conjugated with poly(MPC‐random‐BMA) with 50% BMA units and poly(MPC‐block‐BMA) with 5% BMA units in the near side of the papain maintained much higher enzymatic activity for 28 days at 40°C compared with the papains conjugated with the other polymers. Moreover, the α‐helix content of the papains conjugated with the polymers was maintained at the initial level for 28 days at 40°C. We concluded that the MPC polymers, which contain BMA units, could effectively enhance the stability of papain by controlling the sequence of monomer units and the composition of BMA units in the polymer. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 615–622, 2005     

Synthesis and property of hydrogel membranes consisting of fumaramate with phosphorylcholine group

Fumaramate bearing a phosphoryl choline group, isopropyl‐2‐[2′‐(trimethylammonium) ethyl phosphoryl] ethyl fumaramate (IPTPFA), was radically copolymerized with 2‐hydroxyethylmethacrylate (HEMA) in the presence of various crosslinking agents, water, and 2,2′‐azobis(isobutyronitrile) to obtain hydrogel membranes. The obtained hydrogel membranes adsorbed bovine serum albumin (BSA) much less than those of poly(HEMA), and the values of water content (H) were higher than those of poly(HEMA). The values of tensile strength and tensile elongation of the hydrogel were 68.4 g/mm² and 239%, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2552–2557, 2004