Porous poly(ethylene glycol)–polyurethane hydrogels as potential biomaterials

We report the synthesis of porous poly(ethylene glycol)–polyurethane (PEG‐PU) hydrogels using PEG‐4000 as a soft segment and 4,4′‐methylenebis(cyclohexylisocyanate) as a hard segment. The degree of swelling in the hydrogels could be controlled by varying the amount of crosslinking agent, namely 1,2,6‐hexanetriol. Structural characterization of the hydrogels was performed using solid‐state ¹³C NMR and Fourier transform infrared spectroscopy. Wide‐angle X‐ray diffraction studies revealed the existence of crystalline domains of PEG and small‐angle X‐ray scattering studies showed the presence of lamellar microstructures. For generating a porous structure in the hydrogels, cryogenic treatment with lyophilization was used. Scanning electron microscopy and three‐dimensional micro‐computed tomography imaging of the hydrogels indicated the presence of interconnected pores. The mechanical strength of the hydrogels and xerogels was measured using dynamic mechanical analysis. The observed dynamic storage moduli (E′) for the equilibrium swollen and dry gels were found to be 0.15 and 4.2 MPa, respectively. Interestingly, the porous PEG‐PU xerogel also showed E′ of 5.6 MPa indicating a similar mechanical strength upon incorporating porosity into the gel matrix. Finally, preliminary cytocompatibility studies showed the ability of cells to proliferate in the hydrogels. These gels show promise for applications as scaffolds and implants in tissue engineering. © 2014 Society of Chemical Industry     

Enhancing expanded poly(tetrafluoroethylene) (ePTFE) for biomaterials applications

Poly(tetrafluoroethylene) (PTFE), a fully fluorinated linear thermoplastic polymer, and in particular the porous form expanded PTFE (ePTFE) has found widespread use in biomaterials application due to its properties of high toughness, non‐adhesiveness and hydrophobicity. While it performs ideally for many applications, some challenges have been identified for its use in small diameter vascular grafts and as a tissue space‐filler for cosmetic reconstructions where the implant interfaces with bone. For these applications modification of the surface of ePTFE has been investigated as a means to enhance its performance. This review will focus on the applications listed above and will detail methods of evaluating the biological response, methods used to enhance the surface properties of ePTFE, and how the modified materials have performed in their intended applications. This review will focus on work published from 2004 onwards. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40533.     

A novel biodegradable amphiphilic diblock copolymers based on poly(lactic acid) and hyaluronic acid as biomaterials for drug delivery

An amphiphilic poly((lactic acid)-b-hyaluronic acid) diblock copolymer, poly(LA-b-HA), was synthesized from short-chain hyaluronic acid and poly(lactic acid). The synthesis was conducted by coupling the N, N′- dicyclohexylcarbodiimide activated poly(lactic acid) to a short-chain hyaluronic acid which was pre-aminated with 1, 2-ethylenediamine at the reducing end followed by NaCNBH₃ reduction. The poly (LA-b-HA) copolymers synthesized were verified by the spectral analyses of FTIR and ¹H NMR. The poly(LA-b-HA) molecules can self-assemble into micelles in aqueous solution. The average diameters of polymeric micelles were estimated to be 116 ± 17 and 98 ± 11 nm for the polymeric micelles derived from the poly(lactic acid)s of MW 3,200 and MW 16,900, respectively. The poly(LA-b-HA) copolymeric material is non-cytotoxic and can be used as micellar drug carriers. The drug encapsulation capabilities of these poly(LA-b-HA) micelles were demonstrated by using ellagic acid and lidocaine chloride as model compounds. These new biodegradable micelles have a great potential to be used as drug delivery carrier for biomedical applications.     

Investigation of poly(methyl acrylate) grafted chitosan as a polymeric drug carrier

The graft copolymerization of methyl acrylate (MA) onto chitosan in aqueous medium was investigated using potassium persulfate (KPS) as initiator. The grafting conditions were optimized by studying the effects of the polymerization variables (the initiator concentration, the ratio of monomer to chitosan, and reaction temperature) on the percentage of grafting (PG). PG was found to depend on these variables, and the highest grafting percentage (256 %) could be obtained at chitosan = 1 g, KPS = 4.5 × 10^?3 M, methyl acrylate monomer = 6 g, T = 60 °C and t = 180 min. The graft copolymer was characterized by Fourier transform infrared spectra analysis, thermogravimetry (differential thermogravimetry, differential scanning calorimetric), X-ray powder diffraction as well as CP-MAS ¹³C NMR spectroscopy. These analyses are highly confirmed the formation of poly(methyl acrylate) grafted chitosan (PMAGC). Furthermore, the gelation of the grafted polymers (PG 68, 122, 218 and 256 %) in distilled water has been studied, and the results revealed that the percentage of swelling number increase with increasing PG of the polymers. Controlled release of niacin (vitamin B₃) from the hydrogel of the grafted polymers (PG 68, 122 and 256 %) in aqueous medium has been studied using ultraviolet absorption to follow quantities released at different times (for each experiment: PMAGC 100 mg, niacin 2.46 mg, distilled water 100 ml). The study was repeated again with same conditions except the using of 4.92 mg of niacin instead of 2.46 mg (PG of the grafted polymer is 256 %). The diffusion coefficient (D, cm²/h) of niacin from the hydrogel of the grafted polymer (PG 256 %) was calculated depending on Higuchi model (diffusion coefficient of the first load is 0.00194 cm²/h while 0.00255 cm²/h of the second load).     

A glow discharge treatment to immobilize poly(ethylene oxide)/poly(propylene oxide) surfactants for wettable and non-fouling biomaterials

A non-fouling (protein resistant) polymer surface was achieved using an argon glow discharge treatment of a polyethylene surface which had been precoated with various poly(ethylene oxide)/poly(propylene oxide)/poly(ethylene oxide) (PEO-PPO-PEO) tri-block copolymer surfactants. The surfactant is first deposited on the polymer surface via a solvent swelling and evaporation method. Then the coated surfactant is immobilized on the substrate surface by an inert gas discharge treatment. ESCA and water contact angle () measurements on treated and solvent washed surfaces show significant increases in both surface O/C ratios and surface water wettability (0 < 30°) compared to LDPE control surfaces, revealing the presence of PEO on the treated surfaces. A great reduction of fibrinogen adsorption on the modified surfaces is also observed for the highest PEO content surfactants. This simple surface modification process may have wide applicability to obtain wettable polymer surfaces in general, and non-fouling biomaterial surfaces in specific.     

Investigation on the crystallization behavior of poly(ether ether ketone)/poly(phenylene sulfide) blends

The morphology of nonisothermally crystallized poly(phenylene sulfide) (PPS) and its blend with poly (ether ether ketone) (PEEK) have been observed by polarized optical microscope (POM) equipped with a hot stage. The nonisothermal crystallization behavior of PPS and PEEK/PPS blend has also been investigated by differential scanning calorimetry (DSC). The maximum crystallization temperature for PEEK/PPS blend is about 15°C higher than that of neat PPS, and the crystallization rate, characterized by half crystallization time, of the PEEK/PPS blend is also higher than that of the neat PPS. These results indicate that the PEEK acts as an effective nucleation agent and greatly accelerates the crystallization rate of PPS. The Ozawa model was used to analyze the nonisothermal crystallization kinetics of PPS and its blends. The Avrami exponent values of neat PPS are higher than that of its blend, which shows that the presence of PEEK changed the nucleation type of PPS from homogeneous nucleation to heterogeneous nucleation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Investigation on the microstructure and the electric property of poly(propylene)/chlorinated poly(propylene)/poly(aniline) composites

The article presents results of studies on composites made from poly(propylene) (PP) modified with poly(aniline) (PANI) doped with dodecylbenzene sulfonic acid (DBSA) and chlorinated poly(propylene) (CPP). The volume resistivity of PP/CPP/PANI composites was detected, and the results show that the volume resistivity decreases with increasing CPP content, and there exists a minimum volume resistivity. Effects of CPP on the microstructure and crystalline structure of the PP/CPP/PANI composites and the relationship between the effects and the electric property were carefully analyzed by scanning electron microscope (SEM) and wide angle X‐ray diffraction (WAXD). The method that the specimens of SEM are polished is appropriate to investigate the morphology of conducting polymer composites. The obtained results illuminate that the area of conducting parts and insulating parts obtained from the digital analysis of the SEM image is obviously influenced by the CPP content, the parameters of the lamellar‐like structure are immediately related to CPP content and denote the dispersion of PANI‐DBSA, and the percent crystallinity and mean crystal size of PP are directly correlated with the CPP content. The increasing area of conducting parts, the increasement of layer distance, the decreasement of size and layer number of the lamellar‐like structure of PANI‐DBSA, and the increasement of the percent crystallinity and mean crystal size of PP are beneficial to the improvement of the conductive property of PP/CPP/PANI composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Investigation on thermoplastic co‐poly(ether‐ester) elastomer toughened poly(methylmethacrylate) blends

Blends of poly(methyl methacrylate) (PMMA) and copoly(ether‐ester) (COPE) elastomer have been prepared in different compositions namely, 95/5, 90/10, 85/15, and 80/20 wt % (PMMA/COPE), by melt mixing technique using twin screw extruder. The influence of COPE content on the mechanical properties especially impact strength, thermal behavior, and chemical resistance of PMMA have been investigated. The impact strength of the PMMA/COPE blends for all the compositions were found to be improved remarkably as compared to the virgin PMMA without affecting the other mechanical properties significantly. Various composite models, such as series model, parallel model, Halpin‐Tsai equation, and Kerner's model have been used to fit the experimental mechanical properties. The effect of chemical and thermal ageing on the performance of the PMMA/COPE blends was also studied. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Silicones as biomaterials

Silicon has the ability to form polymeric chains, commonly linear chains of dimethylsiloxane, although other organic groups can be substituted for methyl. In addition, the properties of the resultant silicone polymers can vary with composition and curing procedure. This leads to a wide range of materials known as the silicones. This group of polymers, which have excellent biocompatibility, have been utilised to develop and manufacture a wide range of biomedical products. These range from simple tubing to complex implants, for example those used to replace diseased finger joints. The versatility of these materials has led to silicone products being employed in almost every medical speciality.     

The effect of poly(ethylene glycol) as plasticizer in blends of poly(lactic acid) and poly(butylene succinate)

The effect of polyethylene glycol (PEG) on the mechanical and thermal properties of poly(lactic acid) (PLA)/poly(butylene succinate) (PBS) blends was examined. Overall, it was found that PEG acted as an effective plasticizer for the PLA phase in these microphase‐separated blends, increasing the elongation at break in all blends and decreasing the T_g of the PLA phase. Significant effects on other properties were also observed. The tensile strength and Young's modulus both decreased with increasing PEG content in the blends. In contrast, the elongation at break increased with the addition of PEG, suggesting that PEG acted as a plasticizer in the polymer blends. Scanning electron microscope images showed that the fracture mode of PLA changed from brittle to ductile with the addition of PEG in the polymer blends. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43044.     

Properties of crosslinked blends of pellethene and multiblock polyurethane containing poly(ethylene oxide) for biomaterials

A series of multiblock polyurethanes, containing various poly(ethylene oxide) (PEO; number‐average molecular weight = 400–3400) contents (0–80 wt %) and prepared from hexamethylene diisocyanate/PEO/poly(dimethylsiloxane) diol/polybutadiene diol/1,4‐butanediol, were used as modifying additives (30 wt %) to improve the properties of biomedical‐grade Pellethene. Different molecular weights of PEO were used to keep poly(ethylene glycol) at a fixed molar content, if possible, although the PEO content, related to the PEO block length in the multiblock polyurethanes, was varied from 0 to 80 wt %. The hydrophilic PEO component was introduced through the addition of PEO‐containing polyurethanes and dicumyl peroxide as a crosslinking agent in a Pellethene matrix. As the PEO content (PEO block length) increased, the hydrogen‐bonding fraction of the crosslinked Pellethene/multiblock polyurethane blends increased, and this indicated an increase in the phase separation with an increase in the PEO content in the crosslinked Pellethene/multiblock polyurethane blends. According to electron spectroscopy for chemical analysis, the ratio of ether carbon to alkyl carbon in the crosslinked Pellethene/multiblock polyurethane blends increased remarkably with increasing PEO content. The water contact angle of the crosslinked Pellethene/multiblock polyurethane blend film surfaces decreased with increasing PEO content. The water absorption and mechanical properties (tensile modulus, strength, and elongation at break) of the crosslinked Pellethene/multiblock polyurethane blend films increased with increasing PEO content. The platelet adhesion on the crosslinked Pellethene/multiblock polyurethane blend film surfaces decreased significantly with increasing PEO content. These results suggest that crosslinked Pellethene/multiblock polyurethane blends containing the hydrophilic component PEO may have potential for biomaterials that come into direct contact with blood. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2348–2357, 2004     

Impact-modified poly(styrene-co-acrylonitrile) blends containing both oxazoline-functionalized poly(ethene-co-1-octene) elastomers and poly(styrene-co-maleic anhydride) as compatibilizer

Blends of a poly(styrene-co-acrylonitrile) (SAN) with poly(ethene-co-1-octene) rubber (EOR) were investigated. An improved toughness–stiffness balance was obtained when adding as a compatibilizer a blend consisting of oxazoline-functionalized EOR, prepared by grafting EOR with oxazoline-functional maleinate, and poly(styrene-co-maleic anhydride) (SMA), which is miscible with SAN. Enhanced interfacial adhesion was evidenced by the improved dispersion of the EOR in the SAN matrix and the reduced glass transition temperature of the dispersed EOR phase. Morphology studies using transmission electron microscopy revealed formation of an interphase between the matrix and the rubber particles. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1685–1695, 1999     

Degradable poly(ester amine) based on poly(ethylene glycol) dimethacrylate and polyethylenimine as a gene carrier

Degradable poly(ester amine) (PEA) based on poly(ethylene glycol) dimethacrylate (PMEG) and polyethylenimine (PEI) were synthesized by Michael addition reaction. The ratios of PEI to PMEG in PEAs were 0.99, 1.02, and 1.07 with corresponding number‐average molecular weight of 1.3 × 10⁴, 1.2 × 10⁴, and 0.9 × 10⁴, respectively. Degradation rate of PEA at pH 7.4 was higher than that at pH 5.6. Good plasmid condensation and protection ability was shown when N/P molar ratio of PEA to DNA was above 15 (N: nitrogen element in PEA, P: phosphate in DNA). PEA/DNA complexes had positive zeta potential, narrow size distribution, good dispersity, and spheric shape with size below 250 nm when N/P ratio was above 30, suggestion of their endocytosis potential. Compared with PEI 25 KDa, the PEAs showed essential nontoxic to HeLa, HepG2 and 293T cells. With an increase in the molecular weight of PMEG, the transfection efficiency of PEAs in HeLa, HepG2 and 293T showed a tendency to decrease as well as the percent decrease of gene transfection efficiency with serum. The mechanism of PEA‐mediated gene transfection was attributed to “proton sponge effect” of PEI in the PEA. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Investigation on the miscibility of the blends of poly(methyl methacrylate) and poly(styrene‐co‐acrylonitrile)

The miscibility was investigated in blends of poly(methyl methacrylate) (PMMA) and styrene‐acrylonitrile (SAN) copolymers with different acrylonitrile (AN) contents. The 50/50 wt % blends of PMMA with the SAN copolymers containing 5, 35, and 50 wt % of AN were immiscible, while the blend with copolymer containing 25 wt % of AN was miscible. The morphologies of PMMA/SAN blends were characterized by virtue of scanning electron microscopy and transmission electron microscopy. It was found that the miscibility of PMMA/SAN blends were in consistence with the morphologies observed. Moreover, the different morphologies in blends of PMMA and SAN were also observed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Process-structure-property relationships of erodable polymeric biomaterials: II—long range order in poly(desaminotyrosyl arylates)

The long-range order of some bioerodable polyesteramides based on a desaminotyrosyl [Thermochim Acta 396 (2003) 141; Polym Adv Technol 13 (2002) 926; J Am Chem Soc 119 (1997) 4553] diol monomer has been investigated. The order is mesogenic, best described as a ‘condis crystal’ or smectic-like. In all cases where long-range order is present, ordered H bonds between amide groups are observed. The order stabilizes the polymer to dimensional change and mechanical relaxation under biorelevant conditions.     

Surface grafting of a poly(organophosphazene) onto poly(vinyl alcohol) and poly(ethylene-co-vinyl alcohol) using triethoxysilane as a coupling agent

Triethoxysilane HSi(OEt)₃ was used as coupling agent to graft a poly(organophosphazene) (POPZ) containing allylic functions to the surface of poly(vinyl alcohol) or poly(ethylene-co-vinyl alcohol) films. Hydrolyzed HSi(OEt)₃, which contained both inorganic (Si–OH) and organic (Si–H) reactivities, acted at the interface between the hydroxylated substrates (via a condensation reaction) and the allylic functions in POPZ (via a hydrosilylation reaction). Starting materials and grafting surfaces were studied by ATR-IR and XPS spectroscopies and contact angle measurements. Data obtained indicated that different POPZ layers were produced, depending on whether the functionalization of materials with silane, and the grafting reaction were separately or simultaneously made. The POPZ layer thickness was higher when the grafting reaction was preceded by the POPZ functionalization. In each cases, the modified surfaces showed marked increases in hydrophobicity character. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1965–1974, 1998     

Hydrogels as smart biomaterials

Hydrogels were the first biomaterials rationally designed for human use. Beginning with the pioneering work of Wichterle and Lím on three‐dimensional polymers that swell in water, we review the design, synthesis, properties, and applications of hydrogels. The field of hydrogels has moved forward at a dramatic pace. The development of suitable synthetic methods encompassing traditional chemistry to molecular biology has been used in the design of hydrogels mimicking basic processes of living systems. Stimuli‐sensitive hydrogels, hydrogels with controlled degradability, genetically engineered poly(amino acid) polymers reversibly self‐assembling in precisely defined three‐dimensional structures, and hybrid polymers composed of two distinct classes of molecules are just some examples of these exciting novel biomaterials. The biocompatibility of hydrogels and their applications from implants to nanomaterials are also reviewed. Copyright © 2007 Society of Chemical Industry     

Investigation on crystallization behavior and hydrophilicity of poly(vinylidene fluoride)/poly(methyl methacrylate)/poly(vinyl pyrrolidone) ternary blends by solution casting

Ternary blends composed of matrix polymer poly(vinylidene fluoride) (PVDF) with different proportions of poly(methyl methacrylate) (PMMA)/poly(vinyl pyrrolidone) (PVP) blends were prepared by solution casting. The crystallization behavior and hydrophilicity of ternary blends were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), wide angle X‐ray diffraction (WAXD), differential scanning calorimetry (DSC), and contact angle test. According to morphological analysis, the surface was full of typical spherulitic structure of PVDF and the average diameter was in the order of 3 μm. The samples presented predominantly β phase of PVDF by solution casting. It indicated that the size of surface spherulites and crystalline phase had little change with the PMMA or PVP addition. Moreover, FTIR demonstrated special interactions among the ternary polymers, which led to the shift of the carbonyl stretching absorption band of PVP. On the other hand, the melting, crystallization temperature, and crystallinity of the blends had a little change compared with the neat PVDF in the first heating process. Except for the content of PVP containing 30 wt %, the crystallinity of PVDF decreased remarkably from 64% to 33% and the value of t_1/2 was not obtained. Besides, the hydrophilicity of PVDF was remarkably improved by blending with PMMA/PVP, especially when the content of PVP reached 30 wt %, the water contact angle displayed the lowest value which decreased from 98.8° to 51.0°. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Investigation of the interpolymer association between poly(vinyl alcohol) and poly(sodium styrene sulfonate) in aqueous solution

A viscosimetric method has been used to study the interpolymer association between poly(vinyl alcohol) (PVA) and poly(sodium styrene sulfonate) (PSSNa) in aqueous solution. At constant molecular weight of PSSNa, it was found that, the PVA and PSSNa associations were improved with the decrease of molecular weight of PVA and the decrease of its hydrolysis degree. The measurement of intrinsic viscosity [η] and the determination of Huggins associative coefficient K_H of different PVA samples were used to select the most appropriate PVA sample, which leads to homogeneous polymer–polymer mixtures (PVA with hydrolysis degree 87–89%, molecular weight 124,000–186,000 g/mol, intrinsic viscosity [η] = 1.02 dL/g, and Huggins associative coefficient K_h.ass = 0.76). The obtained results show that the interpolymer association between PVA and PSSNa, in aqueous solution, is mainly due to intermolecular hydrogen bonds between hydroxyl groups of PVA and sulfonate groups of PSSNa. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Oligoesters based on poly(p‐alkoxycinnamate) and poly(pentaethylene glycol cinnamate) as potential UV filters

Four solid UV‐absorptive oligomers—poly(p‐ethoxycinnamate) ( P2 ), poly(p‐propoxycinnamate) ( P3 ), poly(p‐hexyloxycinnamate) ( P6 ), and poly(p‐undecyloxycinnamate) ( P11 )—were condensation polymerized from p‐(2‐hydroxy‐ethoxy) cinnamic acid, p‐(3‐hydroxy‐propoxy) cinnamic acid, p‐(6‐hydroxy‐hexyloxy) cinnamic acid, and p‐(11‐hydroxy‐undecyloxy) cinnamic acid, respectively. The liquid UV‐absorptive oligomer, poly(pentaethylene glycol cinnamate) (PPGC), was synthesized through the copolymerization between p‐hydroxycinnamic acid and pentaethylene glycol ditosylate. Molecular weights of all five oligomers were in the range of 1600–5500. Absorption profiles of all synthesized polymers indicated UVB absorption characteristics. Upon UVB exposure, trans to cis photoisomerization of all five oligomers was observed, leading to the decrease in their UVB absorption efficiency. No transdermal penetration across a baby mouse skin (Mus musculus Linn.) was detected for the five synthesized oligomers, while the penetration of the standard UVB filter, 2‐ethylhexyl‐p‐methoxycinnamate, through the same skin could be clearly observed. In addition, PPGC, a yellowish water immiscible liquid, showed good solubility in various organic solvents and silicone fluids. PPGC and P3 could be induced into water dispersible nanoparticles using solvent displacement technique. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008