Synthesis and dynamic mechanical properties of heterogeneous network polymers from poly(L-glutamic acid) and poly(oxyethylene glycol)

Heterogeneous network polymers composed of rigid polypeptide chains and flexible polyether chains were synthesized. That is, poly(L -glutamic acid) (PLGA) was crosslinked with poly(oxyethylene glycol) (PEG) at various carboxy/hydroxyl mole ratios K. The solubility tests and hydrolysis of heterogeneous network polymers suggest that the crosslinking reaction proceeds by esterification. The dynamic mechanical properties of these polymers(100 Hz, ?100–200°C) are greatly influenced by the presence of a trace of water and the weight per cent of PLGA. In addition, some of these polymers show only one maximum in the temperature dispersion of dynamic loss modulus E″ and tan δ, although their shape is rather broad. The x-ray photographs of these polymers show an amorphous halo or weak Debye-Sherrer rings. These findings suggest that these polymers are not simple adducts; neverthless PLGA and/or PEG domains exist.     

Fabrication and anti-fouling properties of photochemically and thermally immobilized poly(ethylene oxide) and low molecular weight poly(ethylene glycol) thin films

Poly(ethylene oxide) (PEO) and low molecular weight poly(ethylene glycol) (PEG) were covalently immobilized on silicon wafers and gold films by way of the CH insertion reaction of perfluorophenyl azides (PFPAs) by either photolysis or thermolysis. The immobilization does not require chemical derivatization of PEO or PEG, and polymers of different molecular weights were successfully attached to the substrate to give uniform films. Microarrays were also generated by printing polymer solutions on PFPA-functionalized wafer or Au slides followed by light activation. For low molecular weight PEG, the immobilization was highly dependent on the quality of the film deposited on the substrate. While the spin-coated and printed PEG showed poor immobilization efficiency, thermal treatment of the PEG melt on PFPA-functionalized surfaces resulted in excellent film quality, giving, for example, a grafting density of 9.2×10(-4)?(-2) and an average distance between grafted chains of 33? for PEG 20,000. The anti-fouling property of the films was evaluated by fluorescence microscopy and surface plasmon resonance imaging (SPRi). Low protein adsorption was observed on thermally-immobilized PEG whereas the photoimmobilized PEG showed increased protein adsorption. In addition, protein arrays were created using polystyrene (PS) and PEG based on the differential protein adsorption of the two polymers.     

Easily grafted polyurethanes with reactive main chain functional groups. Synthesis,characterization, and antithrombogenicity of poly(ethylene glycol)-grafted poly(urethanes)

A novel synthesis of poly(ethylene glycol) (PEG)-grafted poly(urethanes) (PURs) is described based on a precursor PUR containing free amino groups in the main chain. Three different poly(urethane) backbones were prepared: a homopoly(urethane) comprised of N-Bocdiethanolamine (BDA) and 4,4′-methylenebis(phenyl isocyanate) (MDI), a copoly(urethane) (COPUR) consisting of BDA, N-benzyldiethanolamine and MDI, and a poly(urethane urea) (PUU) that was prepared from BDA, MDI, and ethylenediamine as the chain extender. The M_n of these poly(urethanes) ranged from 32,000 to 72,000 g/mol. PEG (750, 1,900, and 5,000 g/mol) was grafted onto the boc-deprotected poly(urethanes) via the chloroformate. Films of the polymers were spin cast from dilute solutions, annealed, and the surfaces analyzed by goniometry. Water contact angle data indicates increasing PEG surface coverage of the poly(urethanes) with increasing PEG molecular weight. Reorientation of the polymer films is evidenced by contact angle hysteresis. Polymer thrombogenicity, which was studied using blood perfusion experiments, shows that COPUR-g-PEG5000 and PUU-g-PEG5000 exhibit very little platelet adhesion. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3441–3448, 1999     

UV-curable poly(ethylene glycol)–based polyurethane acrylate hydrogel

Poly(ethylene glycol) (PEG) with molecular weight (M_n) of 1000, 2000, 3000, and 4000 g/mol, four types of diisocyanate [hexamethylene diisocyanate (HDI), 4,4′-dicyclohexylmethane diisocyanate (H₁₂MDI), isophorone diisocyanate (IPDI), and toluene diisocyanate (TDI)], two types of comonomers [acrylamide (AAm) and acrylic acid (AAc)] that comprised up to 60% of the total solid were used to prepare UV-curable PEG–based polyurethane (PU) acrylate hydrogel. The gels were evaluated in terms of mechanical properties, water content as a function of immersion time and pH, and X-ray diffraction profiles of dry and swollen films. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2703–2709, 1999     

Organometallic polymers. I. Synthesis of ferrocene-containing poly(phosphine oxides) and poly(phosphine sulfides)

Poly(phosphine oxides) and poly(phosphine sulfides) of ferrocene were synthesized in the melt phase. The resulting ferrocene polymers, linked by phosphorus bridges, were thermally stable and infusible solids, of low molecular weight (M?_n < 4000). Phenyldichlorophosphine, phenyldichlorophosphonate, and phenylphosphonothioic dichloride were copolymerized with ferrocene in the melt phase (80–110°C.) with ZnCl₂ as a catalyst. As the polymerization temperature was raised, cleavage of cyclopentadiene rings from iron became more pronounced, and cyclopentane-bridged polymers of ferrocene were produced in competition with the ferrocene–phosphorus polymers. The cleavage-polymerization process became predominant at 140°C. The structures of poly(phosphine oxides) (and sulfides) of ferrocene were verified by infrared and nuclear magnetic resonance spectroscopy.     

Synthesis and evaluation of properties of novel poly(benzimidazole‐amide)s

Novel aromatic polyamides have been prepared by a combination of diacids containing preformed benzimidazole rings and aromatic diamines. By the phosphorylation method of polycondensation, polymers of high molecular weight (inherent viscosities between 0.81 and 2.13 dL/g) were obtained, which showed good solubility in polar aprotic solvents. The combination of aromatic amide linkages and benzimidazole rings along the polymer chain endowed the polymers with high thermal resistance and excellent mechanical properties. Glass transition temperatures fell in the range of 290–330 °C as measured by differential scanning calorimetry, and initial decomposition temperatures under nitrogen were over 480 °C as measured by thermogravimetric analysis. Some polymer films showed outstanding tensile strength (over 150 MPa) and moduli (up to 5 GPa). The presence of benzimidazole rings in the current polyamides greatly enhanced their hydrophilicity in comparison with classical wholly aromatic polyamides; thus, although aromatic polyamide films normally show water sorption values of only 4–8%, some of the current poly(benzimidazole amide)s show water sorption up to 19% in a 65% relative humidity atmosphere. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7566–7577, 2008     

Dynamic mechanical behavior of poly(vinyl-methyl ether)-poly(styrene) blends

The dynamic mechanical behavior of 10 and 20% poly(vinyl methyl ether)-polystyrene blends has been studied in the frequency range 10^?5 Hz to 5 Hz and temperature range 100–450 K. Isochronal plots of modulus G′ and loss factor, tan ?, show the presence of one relaxation process at temperatures below the transition zone. A second relaxation process at intermediate temperatures but below T_g may be inferred from the breadth of the G″ frequency curves in the transition zone of both blends. This process, at 280 < T < 300 K, is independent of PVME concentration and seems to be associated with the local modes of motions of PS chains. The rheological behavior of the blends shows them to be compatible up to 20% PVME. Their G′ and G″ data cannot be shifted along a frequency axis to produce a satisfactory master curve. The departure from thermorheological simplicity is much more clearly observed in the tan ? than in the modulus-frequency plots. This departure is due to the change in the segmental correlation effects, or length, with temperature near T_g. A molecular model of the growth of microshear domains with hierarchically constrained molecular motions, given elsewhere, quantitatively agrees with the dynamic mechanical behavior.     

Fluorinated poly(ether sulfone)s

New fluorinated poly(ether sulfone)s were prepared from bisphenols and α,ωbis(4-fluorophenylsulfonyl)perfluoroalkanes. The fluorinated sulfone monomers were synthesized by reaction of 4-fluorobenzenethiol salts with perfluoroalkylene diiodides, followed by oxidation. Sodium carbonate mediated polymerization gave high molecular weight polymers in excellent yield. The polymers are generally soluble in chlorinated hydrocarbons and some dipolar solvents, are amorphous with T_g's in the range of 120–160°C and are stable to 400°C. They form clear, colorless films by solution casting. Cast films have dielectric constants and dissipation factors somewhat below those of typical poly(ether sulfone)s, and show good permeability and selectivity for O₂/N₂ gas separations.     

Preparation and properties of aromatic poly(amide–benzothiadiazine dioxides)

New thermostable poly(amide–benzothiadiazine dioxides) of high molecular weights have been prepared by the two-step cyclopolycondensation of diaminobenzenesulfonamides and aromatic bisacyl chlorides. In the first step, the low-temperature solution polymerization technique afforded open-chain polyamides (I) having high molecular weights. In the second step, the polymeric precursors (I) underwent chemical cyclodehydration in the presence of organic basic catalysts at 160°C to give poly(amide–benzothiadiazine dioxides) (II), whereas thermal cyclodehydration gave unsatisfactory results. Not only the open-chain polymers (I) but also the cyclized polymers (II) were soluble in polar solvents, such as N,N-dimethylacetamide and N-methyl-2-pyrrolidone; tough films were cast from these solutions. Thermogravimetric analyses indicated that the cyclized polymers (II) began to decompose at 450–470°C under nitrogen or in air. It is interesting to note that both polymers I and II exhibited self-extinguishing properties against free flame. The cyclodehydration of model compounds was also investigated.     

Thermoplastic poly(ester‐imide)s derived from anhydride‐terminated polyester prepolymer and diisocyanate

The phase‐separation behavior of thermoplastic poly(ester‐imide) [P(E‐I)] multiblock copolymers, (A‐B)_n, was investigated by a stepwise variation of the imide content. All the multiblock copolymers were synthesized by solution polycondensation with dimethylformamide as a solvent. P(E‐I)s were prepared with anhydride‐terminated polyester prepolymer and diisocyanates. Polyester prepolymers were prepared by the reaction of pyromellitic dianhydride and two different polyols [poly(tetramethylene oxide glycol) (PTMG) and polycaprolactone diol (PCL)]. Structural determination was done with Fourier transform infrared spectroscopy and Fourier transform NMR, and the molecular weight was determined by gel permeation chromatography. The effect of the imide content on the thermal properties of the synthesized P(E‐I)s was investigated by thermogravimetric analysis and differential scanning calorimetry. The polymers were also characterized for static and dynamic mechanical properties. Thermal analysis data indicated that the polymers based on PTMG were stable up to 330 °C in nitrogen atmosphere and exhibited phase‐separated morphology. Polymers based on PCL showed multistage decomposition, and the films derived from them were too fragile to be characterized for static and dynamic mechanical properties. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 341–350, 2004     

Synthesis and properties of poly (diphenylacetylenes) having aliphatic para-substituents

1-(p-t-Butylphenyl)-2-phenylacetylene and 1-(p-n-butylphenyl)-2-phenylacetylene were polymerized in catalytic systems based on TaCl₅ to give new polymers in high yields. These monomers were more reactive than diphenylacetylene (DPA) in copolymerization. Unlike poly (DPA), the present polymers were soluble in toluene, CHCl₃, etc. owing to the high configurational entropy induced by the para-substituents. Their relative weight-average molecular weights determined by GPC were in the range of 6 × 10⁵–36 × 10⁵, and films could be obtained by solution casting. These polymers were fairly thermally stable, as seen from their high onset temperatures (320–380°C) of weight loss in TGA in air. The oxygen permeability coefficient of the polymer with t-Bu group was 1100 barrers, the highest among those of all the hydrocarbon polymers. © 1994 John Wiley & Sons, Inc.     

Group motions in the glassy state of some substituted polystyrenes and poly(vinyl benzoates)

Mechanical damping measurements were carried out in the range of 10³–10⁵ cps and between 60°K. and the softening point on some substituted Polystyrenes and poly(vinyl benzoates) containing different substituents (methyl groups, methoxy groups, and halogen atoms) either in the ring or in the main chain. The ortho and meta ring-substituted polystyrenes do not show any secondary mechanical relaxation in the glassy state, although all the other substituted polystyrenes, exhibit a low-temperature damping peak (δ process) (which is in some way connected with ring motions) whose height and temperature location depend on nature, position, and number of substituents. Substituents in the para position of the ring or in the α position in the backbone chain shift the δ peak of the unsubstituted polystyrene towards higher temperatures; this shift is accompanied by an increase of the apparent activation energy E^*. Substitution in the β position, on the contrary, does not affect the δ peak. Analogous results are obtained for substituted poly(vinyl benzoates), which exhibit, in addition, a β relaxation effect, associated with carboxyl group motions. A very good correlation is found between the values of E* and the limiting relaxation time τ for the δ relaxation of polystyrenes and poly(vinyl benzoates), similarly substituted in the ring, indicating that the δ relaxation leads to absorption curves in the mechanical relaxation spectrum which are characteristic of the structure of the aromatic side chain.     

Strategies toward biocompatible artificial implants: Grafting of functionalized poly(ethylene glycol)s to poly(ethylene terephthalate) surfaces

Epoxide and aldehyde end‐functionalized poly(ethylene glycol)s (PEGs) (M_w = 400, 1000, 3400, 5000, and 20,000) were grafted to poly(ethylene terephthalate) (PET) film substrates that contained amine or alcohol groups. PET‐PAH and PET‐PEI were prepared by reacting poly(allylamine) (PAH) and polyethylenimine (PEI) with PET substrates, respectively; PET‐PVOH was prepared by the adsorption of poly(vinyl alcohol) (PVOH) to PET substrates. Grafting was characterized and quantified by the increase of the intensity of the PEG carbon peak in the X‐ray photoelectron spectra. Grafting yield was optimized by controlling reaction parameters and was found to be substrate‐independent in general. Graft density consistently decreased as PEG chain length was increased. This is likely due to the higher steric requirement of higher molecular weight PEG molecules. Water contact angles of surfaces containing long PEG chains (3400, 5000, and 20,000) are much lower than those containing shorter PEG chains (400 and 1000). This indicates that longer PEG chains are more effective in rendering surfaces hydrophilic. Protein adsorption experiments were carried out on PET‐ and PEG‐modified derivatives using collagen, lysozyme, and albumin. After PEG grafting, the amount of protein adsorbed was reduced in all cases. Trends in surface requirements for protein resistance are: surfaces with longer PEG chains and higher chain density, especially the former, are more protein resistant; PEG grafted to surfaces containing branched or network polymers is not effective at covering the underlying substrate, and thus does not protect the entire surface from protein adsorption; and substrates containing surface charge are less protein‐resistant. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5389–5400, 2004     

Quantitative analysis of biodegradable amphiphilic poly(L-lactide)-block-poly(ethyleneglycol)-blockpoly(L-lactide) by using TG, FTIR and NMR

The thermogravimetric analysis (TG) of two series of tri-block copolymers based on poly(L,L-lactide) (PLLA) and poly(ethyleneglycol) (PEG) segments, having molar mass of 4000 or 600 g mol^–1, respectively, is reported. The prepared block copolymers presented wide range of molecular masses (800 to 47500 g mol^–1) and compositions (16 to 80 mass% PEG). The thermal stability increased with the PLLA and/or PEG segment size and the tri-block copolymers prepared from PEG 4000 started to decompose at higher temperatures compared to those copolymers from PEG 600. The copolymers compositions were determined by thermogravimetric analysis and the results were compared to other traditional quantitative spectroscopic methods, hydrogen nuclear magnetic resonance spectrometry (¹HNMR) and Fourier transform infrared spectrometry (FTIR). The PEG 4000 copolymer compositions calculated by TG and by ¹HNMR, presented differences of 1%, demonstrating feasibility of using thermogravimetric analysis for quantitative purposes.     

Phase-mixed poly(ethylene glycol)/poly(trimethylolpropane triacrylate) semi-interpenetrating polymer networks obtained by rapid network formation

Semi-interpenetrating polymer networks (semi-IPNs) of poly(ethylene glycol) (PEG) in poly(trimethylolpropane triacrylate) (TMPTA) were synthesized from PEG melts in neat TMPTA monomer, using PEG of molecular weights from 4000 to 100,000 g/mol. Differential scanning calorimetry and transmission electron microscopy were used to examine phase separation occurring during network formation. The degree of phase separation was observed to depend upon the rate of PEG aggregation relative to the rate of network formation during TMPTA polymerization. Higher molecular weight PEG and acrylate-functionalized PEG formed more phase-mixed networks compared to lower molecular weight PEG; acetatefunctionalized PEG showed no difference from unmodified PEG in the extent of phase mixing. For networks that demonstrated phase separation, the PEG was observed to be in two states: some being phase mixed and solvent inextractable, and some being phase separated and solvent extractable. Phase-mixed networks could be obtained from this thermodynamically incompatible polymer pair utilizing rapid photopolymerization systems to overcome PEG phase aggregation and kinetically entrap the PEG in a nonequilibrium phase-mixed state. These mixed-phase semi-IPNs of PEG and TMPTA may be useful in biological applications where the presence of PEG is desired throughout the bulk matrix rather than as a surface graft to reduce biological interactions. © 1994 John Wiley & Sons, Inc.     

Synthesis,doping, and processing of high molecular weight poly(o-methoxyaniline)

High molecular weight poly(o-methoxyaniline) was synthesized using a novel method in which the polymerization occurs in the presence of a neutral salt. The molecular weight of the polymer was greatly affected by the quenching procedure employed to conclude the polymerization. Conventional doping of the base form of poly(o-methoxyaniline) produced a yellow coloration of the doping solution and polymer degradation. It was found that the molecular weight of the polymer decreased significantly after washing or doping with certain aqueous acid media. The gelation conditions of N-methyl pyrrolidinone (NMP) solutions and film preparation were also investigated for polymers of various molecular weights. The gelation time in NMP decreased drastically with the increase in the polymer molecular weight (the same for solution concentration and temperature), until a critical point was reached after which its decrease was very slow. Flexible, free-standing, and stretchable films were readily obtained from the higher molecular weight polymers. Good quality doped gel films with conductivity of up to 1 S/cm were obtained under optimized doping conditions. © 1994 John Wiley & Sons, Inc.     

Synthesis and characterization of a multiblock copolymer of poly(N-isovaleryl ethyleneimine) and poly(ethylene glycol)

Block copolymers of poly(N-isovaleryl ethyleneimine) (PiVEI) and poly(ethylene glycol) (PEG) were synthesized by coupling previously prepared blocks of PEG ditosylate with the dianion of the dihydroxy PiVEI. On the average four blocks coupled together to form the final block polymer. The PiVEI blocks crystallized with the same melting points as in the homopolymer. This restricted the mobility of the PEG blocks and they did not crystallize unless cooled well below room temperature. The mechanical properties of cast films were quite good with a tensile strength of 77 kg/cm² and an elongation of 120%. The swelling of unoriented and oriented films with water was studied. The unoriented polymer absorbed about its own volume of water, even though PEG comprised only 40% of the total polymer.     

Polymers derived from fluoroketones. III. Monomer synthesis,polymerization, and wetting properties of poly(allyl ether) and poly(vinyl ether)

The synthesis and polymerization of a series of perhaloalkyl allyl and vinyl ethers derived from perhaloketones is described. Data on the critical surface tension of wetting (γ_c) for high molecular weight polymers of heptafluoroisopropyl vinyl ether and low molecular weight poly(heptafluoroisopropyl allyl ether) is also presented. Preparation of the allyl ethers is a one-step, high-yield displacement reaction between the potassium fluoride–perhaloacetone adduct and an allyl halide, such as allyl bromide. The vinyl ethersare prepared by a two-step process which involves displacement of halide from a 1,2-dihaloethane with a KF–perhaloacetone adduct and dehydrohalogenation of the 1-halo-2-perhaloalkoxyethane to a vinyl ether. Low molecular weight polymers were obtained with heptafluoroisopropyl allyl ether by using a high concentration of a free-radical initiator. The low molecular weight poly(heptafluoroisopropyl allyl ether) had a γ_c of 21 dyne/cm. No polymer was obtained with tributylborane–oxygen or with VCl₃–AIR₃, with gamma radiation, or by exposure to ultraviolet light. High molecular weight polymers were obtained from heptafluoroisopropyl vinyl either by using either lauryl peroxide or ultraviolet light but not by exposure to BF₃–etherate. The γ_c for poly(heptafluoroisopropyl vinyl ether) ranged from 14.2 to 14.6 dyne/cm., and the significance of this value is discussed in relation to the γ_c for poly(heptafluoroisopropyl acrylate).     

Interconversion between mechanical and dielectric relaxations for poly(cyclohexyl acrylate)

Storage E′ and loss E″ relaxation moduli are reported as functions of frequency for poly(cyclohexyl acrylate) (PCA) at several temperatures. The possibility that these results, in conjunction with the dipolar correlation coefficient, can be used to predict the frequency dependence of the real ε and loss ε″ and the components of the complex dielectric permittivity ε* of PCA is studied. A relation between ε* and the complex relaxation modulus E* is obtained by assuming that the lag of the rotating dipoles in the electric field is caused by both dielectric and mechanical friction. The values of ε* obtained from mechanical results by means of this expression are very close to those obtained from other relations based on the assumption that the lag of the dipoles is caused exclusively by mechanical friction. © 1993 John Wiley & Sons, Inc.     

Thermogelling polymers composed of poly(cyclohexylenedimethylene adipate) and poly(ethylene glycol)

Block copolymers composed of hydrophilic poly(ethylene glycol) (PEG) and hydrophobic biodegradable polyesters have been reported as thermogelling polymers, because they feature temperature-dependent sol-to-gel or gel-to-sol transitions in aqueous solutions. In this study, a series of thermogelling poly(ethylene glycol methyl ether)-block–poly(cyclohexylenedimethylene adipate)-block–poly(ethylene glycol methyl ether) triblock copolymers and PEG-block–poly(cyclohexylenedimethylene adipate) multiblock copolymers was synthesized by reacting hydroxyl-terminated poly(cyclohexylenedimethylene adipate) (PCA) with poly(ethylene glycol methyl ether) and PEG, respectively, using 1,6-diisocyanatohexane as the coupling agent. Two hydroxyl-terminated PCAs, i.e., poly(1,4-cyclohexylenedimethylene adipate) and poly(1,3/1,4-cyclohexylenedimethylene adipate), were synthesized by the condensation reaction of adipic acid (AA) with 1,4-cyclohexanedimethanol (CHDM) and 1,3/1,4-CHDM, respectively, and used as the hydrophobic polyester blocks of these thermogelling copolymers to compare the effect of crystallinity on the sol-to-gel transition behavior.The polymers were characterized using proton nuclear magnetic resonance, Fourier transform infrared spectroscopy, gel permeation chromatography, differential scanning calorimetry, solubility testing, and rheological analysis. Experimental results revealed that the structure of the PCA block (crystalline vs. amorphous), the molecular weights of the hydrophobic PCA and hydrophilic PEG blocks, and the type of thermogelling polymer (triblock vs. multiblock) influenced the solubility, polymer micelle packing characteristics, maximum storage modulus, and sol-to-gel temperature of the polymers. Among all the samples at 40 wt.% aqueous solutions, triblock copolymer TB3 showed sol-to-gel temperature at 22 °C, and had the highest maximum storage modulus about 170 Pa.