摘要:

A solution of a random copolymer showing polydispersity only with respect to chemical composition is considered. A model distribution very flexible in its breadth and in its asymmetry is used to describe the polydispersity. Based on continuous thermodynamics, equations for the cloud-point curve, the shadow curve, the spinodal, the critical point, and the heterogeneous double critical point are derived. the activity coefficients are calculated with the aid of Huggins' χ-parameter concept assuming χ to depend linearly on the average chemical composition of the copolymer. the influence of the breadth and the asymmetry of the distribution on the liquid-liquid equilibrium of the copolymer solution is discussed.

ISSN:0022-233X    

DOI:10.1080/10601329008544807

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Graft copolymerization of 2-hydroxyethyl methacrylate onto polypropylene monofilament was carried out by using a simultaneous gamma radiation technique from a60Co source, so that the hydrogel polypropylene-g-polyhydroxyethyl methacrylate thus produced by grafting could be used as a biocompatible suture material. the influence of various parameters, such as dose rate, total dose, and monomer concentration, on the degree of grafting was determined. It was found that the degree of grafting increases with an increase in monomer concentration. However, for a constant dose under optimum monomer concentration (1.5–2.0 mol/L), a low dose rate produces better graft levels. the studies showed that grafting is strongly influenced by the reaction medium. the optimum conditions for the system were determined. the grafting was ascertained by infrared spectroscopy and color formation with methylene blue. the grafted monofilament showed very good swelling behavior in water due to the incorporation of hydrophilicity in the copolymer monofilament.

ISSN:0022-233X    

DOI:10.1080/10601329008544808

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

endo-N-Benzylbicyclo[2,2,1]hept-2-ene-5,6-dicarboximide (BZN orendo-BZN), one of the norbornene derivatives, was prepared fromN-benzylmaleimide (BZMI) and cyclopentadiene (CPD) according to the Diels-Alder reaction. Yields of homopolymers, insoluble in methanol, were about 20 wt%. No BZN could be polymerized in bulk without radical catalysts under 220°C. At 220°C for 1 h,endo-BZN was converted toexo-BZN in a 50-mol% yield. the polymerization of BZN over 300°C for 1 h gave the polymer in about 100% yield. It was found that the polymer consisted of a mixture of BZN, BZMI, and an adduct obtained from BZN and CPD. BZN was copolymerized with styrene, methyl methacrylate, and vinyl acetate with radical initiators. the copolymerizabilities of BZN with VAc were better than those for other systems. the monomer reactivity ratios and Alfrey-PriceQ-evalues were determined.

ISSN:0022-233X    

DOI:10.1080/10601329008544809

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Viscometric, pH, optical, and calorimetric titration studies of an alternating copolymer of maleic acid and indene in aqueous NaCl of 0.01 to 0.27Mat 15 to 35°C showed the conformational transition of a compact to an expanded coil upon ionization of the primary carboxyl groups. the thermodynamic parameters of the transition were calculated. the results indicate that the bulky and inflexible side chain in indene sterically interferes with the formation of the compact form of the copolymer, but stabilizes the low entropic hydrophobic region.

ISSN:0022-233X    

DOI:10.1080/10601329008544810

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The polymerization of vinyl monomers initiated by poly[3-dimethyl-(acryloyloxyethyl)ammonium propane sulfonate], poly(DAAPS), in aqueous solution was studied under vacuum at 85°C. the polymerization proceeds via a radical mechanism without any further initiator. the polymerization is thought to start with the formation of hydrophobic areas with poly(DAAPS) in the aqueous phase. the initiation mechanism involving hydrogen atom transfer is proposed. the effects of the efficiency of grafting, pH, overall activation energy, and the amount of water content and betaine polymer on the polymerization were investigated. A good linear relationship was obtained between the mass of vinyl monomers and the rate of polymerization (Rp) by applying the Michaelis-Menten equation.

ISSN:0022-233X    

DOI:10.1080/10601329008544811

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A-B Type block copolymer ofN-vinylpyrrolidone (NVP) and 4-vinylpyridine (VPy) [poly(NVP-b-VPy) and graft copolymers of VPy onto copolymers of NVP with 4-vinylbenzylN,N-diethyldithiocarbamate (VBDC) [poly(NVP-g-VPy) were synthesized by the iniferter method. the compatibility between NVP and VPy units in the copolymers was evaluated from the glass transition temperature of these copolymers. Hydroquinone was then oxidized by the synthesized NVP-VPy copolymers-Cu(II) complex catalysts. the influence of the distribution of each monomer unit in copolymers on the catalytic activity was studied by comparing the activity of these copolymers. the catalytic activity of these copolymers increased in the order: NVP-VPy blend polymer, poly(NVP-b-VPy), poly(NVP-g-VPy), random copolymer [poly(NVP-ran-VPy)]. This order parallels the compatibility between NVP units and VPy units in these copolymers.

ISSN:0022-233X    

DOI:10.1080/10601329008544812

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

An attempt was made to prepare a graft copolymer consisting of poly(methyl vinyl ketone) (PMVK) as a backbone chain and polyacrylonitrile, poly(4-vinylpyridine), or polystyrene as a graft chain by UV irradiation of a solution of PMKV in the presence of acrylonitrile, 4-vinylpyridine, or styrene. the influence of reaction conditions on the yield, composition, and viscosity of the resulting graft copolymers was investigated. It was suggested from NMR and gel permeation chromatography that those graft copolymers contained a high molecular weight fraction of narrow distribution and block copolymers as well. the reverse osmosis membranes derived from the oxime and amidoxime of the graft copolymers showed a characteristic performance of exhibiting a maximal difference between rejections against NaCl and CoCl2at a certain addition ratio of crosslinking agent, which was not observed in the membranes from copolymers by conventional radical copolymerization. the relationship between these phenomena and the branching structure of the graft copolymers was discussed.

ISSN:0022-233X    

DOI:10.1080/10601329008544813

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The structure and protonation level of the chemically synthesized 2-chloroaniline and 2-iodoaniline homopolymers and their copolymers with aniline have been studied. the results indicate there is no elimination of the substituent group and the polymerization probably occurs at the para-position. the protonation level of the copolymers decreases substantially when the fraction of substituted aniline units is above 0.5, and the electrical conductivity of the copolymers decreases rapidly with an increase in the fraction of substituted aniline units. the protonation level is also lower when HCl rather than H2SO4is used as the protonating acid species, and a significant fraction of the chlorine incorporated is covalently bonded to the polymer. the Nls core-level spectra of the copolymer and the haloaniline homopolymer bases reveal that their imine/amine ratio is substantially lower than that of the polyaniline base. the copolymers show partial solubility in chloroform, but the electrical conductivity of the chloroform-treated samples is not significantly different from that of the pristine sample. When the copolymers synthesized in HCl are heated to 150°C, a fraction of the ionic chlorine is converted to covalently bonded species, resulting in a substantial decrease in the electrical conductivity.

ISSN:0022-233X    

DOI:10.1080/10601329008544814

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The agitation effect on the heterogeneous graft copolymerization of a mixture of vinyl acetate and methyl acrylate onto cellulose was studied. Two procedures for the addition of the reactants were employed. Stirring speed, agitation time, and magnetic as well as mechanic stirring were tested. This polymerization system undergoes significant changes in the reaction parameters under low and high stirring speeds as well as under short agitation times. An explanation of the results is given.

ISSN:0022-233X    

DOI:10.1080/10601329008544815

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The effects of monomer concentration and feed composition in the graft copolymerization of a mixture of vinyl acetate (VAc) and methyl acrylate (MA) onto cellulose, initiated by ceric ion, are studied. Two procedures for the reactants addition were employed and several grafting parameters were measured. MA is more reactive toward grafting than VAc, and the VAc-MA mixture shows an intermediate behavior. Minor amounts of MA favor VAc grafting, and minor amounts of VAc disfavor MA grafting. VAc is oxidated more easily by ceric ion than is MA. An explanation of the results is presented.

ISSN:0022-233X    

DOI:10.1080/10601329008544816

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor