Swelling kinetics and release characteristic of crosslinked chitosan: Polyether polymer network (semi-IPN) hydrogels

The aqueous swelling kinetics of a series of crosslinked chitosan (cr-CS) with glutaraldehyde (GA) interpenetrating polyether hydrogels have been studied as functions of pH, the N-deacetylation degree of chitosan, the amount of crosslinking agent, the electrolyte composition in solution, temperature, and gel composition. Based on these results, the swelling mechanism of the hydrogels was discussed. The release profiles of chlorhexidini acetas from the semi-IPN were also investigated. © 1994 John Wiley & Sons, Inc.     

Microstructure,Rheology, and Potential Oil Absorbency of Poly(Butyl Methacrylate) and Poly(Hydroxyethyl Methacrylate) Blends

To prepare oil-absorptive polymers with moderate cross-linking structure, poly(butyl methacrylate) (PBMA) was synthesized as a linear hydrophobic polymer by suspension polymerization. In addition, hydroxyethyl methacrylate (HEMA), as a monomer, which could construct a network structure among the macromolecules via hydrogen bond interactions, was solution polymerized in dimethylacetamide (DMAc) with PBMA, yielding a polymer blend of PBMA and PHEMA. The solution of the polymer blend was investigated by rotational viscometry and extended rheometry. The results showed that the viscosity varied greatly with the temperature and shear rate for three different compositions. Fourier transform infrared (FTIR) spectra indicated that an entanglement or interlocking cross-linking structure of molecular chains was constructed by hydrogen bonds. The results from nuclear magnetic resonance (NMR) spectra exhibited a downfield movement of the proton peak as influenced by end groups or hydroxyls in the polymer chains. The rheological measurements demonstrated that the cross-linking structure greatly affected the rheological behavior of the blend solution. In addition, the cross-linking structure was also evaluated by oil absorbency of films.     

蓖麻油聚氨酯和乙烯类聚合物互穿网络材料的生成特点及其动态力学性能

研究蓖麻油聚氨酯/取代乙烯共聚物的互穿网络物(IPN)的生成特点指出,其中取代乙烯游离基共聚的氧化还原引发剂组份-过氧化苯甲酰或二甲基苯胺都能加速聚氨酯网络(Pu)的生成。反应温度在 30℃以上蓖麻油也能参与游离基共聚。蓖麻油不仅与TDI反应生成Pu网络,而且也有小部分参与取代乙烯共聚物长枝链的形成。Pu网络的形成较长枝链的生成为快。生成Pu网络时所放出的热促进取代乙烯与少量蓖麻油的双键共聚,最后生成的IPN不溶于甲苯。这表明生成的是接技的半IPN,而不是单纯的半IPN。动态力学研究指出,包含聚苯乙烯或聚甲基丙烯酸甲酯的这种IPN呈现二个T_g,而只包含聚丙烯腈的仅一个T_g,说明后一IPN中相容性较好,有较多的分子混合。随着聚氨酯与聚取代乙烯的比例减少,二个T_g间的差距减少,而较高温度的T_g随取代乙烯共聚物中丙烯腈含量增加而变小。     

Synthesis and Characterization of Self-oscillating P（AA-co-AM）/PEG SemiIPN Hydrogels Based on a p H Oscillator in Closed System

Various semi-interpenetrating polymer network（semi-IPN） hydrogels composed of pore-forming agent polyethylene glycol（PEG）, acrylic acid（AA） and acrylamide（AM） were prepared by using free radical polymerization with a two-step method. The chemical structures of the synthesized hydrogels were characterized by FTIR spectroscopy and the morphologies were studied by scanning electron microscopy（SEM） method. The swelling properties, such as the p Hresponsive behavior, salt sensitivity, oscillatory swelling/de-swelling behaviors in different solutions with various p H values and self-oscillating behaviors in bath p H oscillator were investigated in detail. The results revealed that the prepared hydrogels exhibited high p H sensitivity and excellent salt sensitivity when the p H values of the medium changes from 3.0 and 7.0 and well reversible properties by undergoing a number of swelling/de-swelling recycles. In particular, the hydrogels exhibited self-oscillation behavior in a closed system containing Br O3？-SO32？-Fe（CN）64？-H＋. This study may create a new possibility as biomaterial for new self-walking actuators and other devices.     

Sulfonated Poly(ether ether ketone) and Poly(ethylene glycol) Diacrylate Based Semi-Interpenetrating Network Membranes for Fuel Cells

Polymer electrolyte membranes are prepared from novel semi-interpenetrating polymer network material where the sulfonated poly (ether ether ketone) (SPEEK) is the linear polymer and the poly (ethylene glycol) diacrylate (PEGDA) is the cross-linking constituent. The semi-IPN is prepared by in situ polymerization of PEGDA in the presence of sulfonated poly (ether ether ketone). SPEEK is prepared by direct sulfonation of commercial PEEK (Gatone? 1100) by reported procedures. SPEEK with degree of sulfonation 63% (calculated from FT-NMR) is selected as the base membrane and different semi-IPN membranes were prepared by varying the PEGDA and SPEEK ratio. The degree of sulfonation of SPEEK and the formation of semi-IPN were confirmed by spectroscopy studies. The various semi-IPN membranes were characterized for ion-exchange capacity, water uptake, hydrolytic stability, proton conductivity and thermal stability for evaluating the suitability of these membranes for fuel cells. The proton conductivity of the membranes decreased with increasing PEGDA content. The Semi-IPN membranes exhibited conductivities (30°C) from 0.018 S/cm to 0.006 S/cm. These interpenetrating network membranes showed higher hydrolytic stability than the pure SPEEK membrane. This study shows that semi-IPN membranes based on PEGDA and SPEEK can be viable candidates for electrolyte membranes.     

Compatibility and crystallization in poly(ethylene oxide)-poly(methyl methacrylate) semi-interpenetrating polymer network

Differential scanning calorimetry together with dynamic mechanical analysis were employed to investigate the crystallinity and the miscibility in poly(ethylene oxide)/crosslinked poly(methyl methacrylate) semi-IPN (interpenetrating polymer networks). The crystallinity of poly(ethylene oxide) in the semi-IPN is found to depend on the crosslink density of PMMA as well as the overall content of PEO. Of special interest is that an increase in the crosslink density tends to increase the crystallinity contrary to our expectation, indicating crystallization and phase separation may proceed simultaneously during IPN formation. The investigation of glass transition behaviors with dynamic mechanical analysis suggests phase separation (i.e., there exist two amorphous phases: one PEO-rich phase, the other a PMMA-rich phase). © 1993 John Wiley & Sons, Inc.     

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.     

壳聚糖-聚乙烯基恶唑啉半互穿聚合物网络(semi-IPN)膜对pH的刺激响应性

研究了壳聚糖－聚乙烯基恶唑啉半互穿聚合物网络膜对ＰＨ值的敏感性,发现该膜在ＰＨ〈６时溶胀度迅速增加,在ＰＨ＝３．２时达到最大值;膜在不同ＰＨ值溶液中可交替溶胀收缩,且这种溶胀－收缩行为重复可逆。