已为您找到该学者10条结果 成果回收站
程镕时, LIU Quanwei, LI Yi, WANG Zhiliu, XIE Hongfeng, YANG Hu, CHENG Rongshi
高分子学报,2005,(4):484~485,-0001,():
-1年11月30日
In order to investigate the property and concentration dependence of dissociation and hydrolysis of polyelectrolytes, acrylic acid-sodium acrylate copolymers with various degree of neutralization were prepared by adding calculated amounts of sodium hydroxide into the aqueous solutions of a poly(acrylic acid) sample, and the pH values of the solutions covering a wide concentration range were measured for each copolymer at 25℃. It was found that the pH values of the solutions of a copolymer with degree of neutralization of 0.96 kept constant and equaled to 9.80 as c>0.001mol/L. For another copolymer with degree of neutralization of 0.30, the pH values of its solutions remained constant and equaled to 6.25 as c<0.001mol/L. These two copolymers may serve as polymeric buffer reagents which couldn't penetrate through semi-permeable membranes in the corresponding concentration regions.
聚电解质,, 离解,, 高分子缓冲溶液
-
45浏览
-
0点赞
-
0收藏
-
0分享
-
122下载
-
0
-
引用
程镕时, Weisi Yin, , Hu Yang, Xueqin Zhang, Zhiliu Wang, Yanwei Ding, Guangzhao Zhang, Rongshi Cheng
,-0001,():
-1年11月30日
The special thermosensitive copolymer with lower critical solubility temperature near human heat of 37℃ in aqueous solution has been prepared successfully by copolymerizing N-isopropylacrylamide (NIPAM) and N-isopropylmethacrylamide (NIPMAM) randomly at an appropriate monomer ratio. The self-association behavior of the poly[NIPAM-ran-NIPMAM] copolymer has been studied by dynamic laser light scattering (DLLS) at a concentration higher than the critical concentration of the self-association calculated from viscosity data according to cluster theory. The effect of the concentration and temperature on the self-association behavior in water has been discussed respectively.
copolymerization, thermosenstitive copolymer, self-association, cluster theory, viscosity, dynamic laser light scattering
-
55浏览
-
0点赞
-
0收藏
-
0分享
-
97下载
-
0
-
引用
程镕时, Hu Yang, , Weisi Yin, Xueqin Zhang, Zhengchun Cai, Zhiliu Wang, Rongshi Cheng
Journal of Applied Polymer Science, Vol. 96, 2454-2458 (2005),-0001,():
-1年11月30日
The growth of poly (ethylene oxide) (PEO) spherulites was observed synchronously with a polarized optical microscope, which was equipped with a video detector, and so the whole growing process of the PEO spherulites was dynamically recorded as a movie. There was a series of concentric diffractive bands on the surface of the PEO spherulites; furthermore, the diffractive banding did not exist until at least two independent PEO spherulites came into contact with each other. However, the formation of the diffractive banding on the PEO spherulites was also related to the crystallization conditions. It was concluded qualitatively that the diffractive banding formed more easily at the crystallization temperature with a high degree of supercooling, and this was explained in kinetic terms.
spherulites, structure, water-soluble polymers
-
43浏览
-
0点赞
-
0收藏
-
0分享
-
123下载
-
0
-
引用
【期刊论文】States of water in partially swollen poly(vinyl alcohol) hydrogels
程镕时, Wenbo Li a, Feng Xue a, Rongshi Cheng a, b, *
Polymer 46 (2005) 12026-12031,-0001,():
-1年11月30日
A poly(vinyl alcohol) hydrogel was prepared by coupling poly(vinyl alcohol) with epichlorohydrin as cross-linking agent. Various amounts of water were added into the dry hydrogel to swell it and the quantity of water in various states in the partially swollen hydrogel were determined by DSC ice-melting technique. A parameter S denoted the degree of the saturation of swelling was introduced for describing the various stages of water absorption. The analytical results indicate that there exists two critical threshold degree of saturation. At the first threshold S*, the freezable bound water starts to appear and at the second threshold S**, the free water begins to appear. In the region of S!S*, the adsorbed water exists only in the non-freezable form and increases linearly with S until reaching S*. The sum of non-freezable and freezable bound water consists of the hydration layer around the chain segments of the network. The hydration number HN of the repeating unit of PVA hydrogel increases from zero to a limiting value about 2.5 as the degree of saturation varies from zero to one.
DSC, States of water, Saturation of swelling
-
54浏览
-
0点赞
-
0收藏
-
0分享
-
490下载
-
0
-
引用
程镕时, XUEQIN ZHANG, , HU YANG, QUANWEI LIU, YUN ZHENG, HONGFENG XIE, ZHILIU WANG, RONGSHI CHENG
,-0001,():
-1年11月30日
Biodegradable poly(tert-butyl acrylate)–poly[(R)-3-hydroxybutyrate]–poly (tert-butyl acrylate) triblock copolymers based on bacterial poly[(R)-3-hydroxybutyrate] (PHB) were synthesized by atom transfer radical polymerization. The chain architectures of the triblock copolymers were confirmed by 1H NMR and 13C NMR spectra. Gel permeation chromatography analysis was used to estimate the molecular weight characteristics and lengths of the PHB and poly(tert-butyl acrylate) blocks of the copolymers. The thermal properties of the copolymers were studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). TGA showed that the triblock copolymers underwent stepwise thermal degradation and had better thermal stability than their respective homopolymers, whereas DSC analyses showed that a microphase-separation structure was formed only in the triblock copolymers with the longer PHB block. As a similar result, from wide-angle X-ray diffraction experimentation, the crystalline phase of PHB could not be seen evidently in the triblock copolymers with the shorter PHB block. The enzymatic hydrolysis of the copolymer films was carried at 378C and pH7.4 in a potassium phosphate buffer with an extracellular PHB depolymerase from Penicillum sp. The biodegradability of the triblock copolymers increased with an increase in the PHB block content.
atom transfer radical polymerization (, ATRP), , biodegradable, characterization, poly (, tert-butyl acrylate), -poly[(, R), -3-hydroxybutyrate]-poly(, tert-butyl acrylate), (, PtBA–PHB- PtBA), triblock copolymers, synthesis
-
0浏览
-
0点赞
-
0收藏
-
0分享
-
378下载
-
0
-
引用