ISSN:0022-233X    

DOI:10.1080/00222339009349563

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Oxepane-2,7-dione (1) was prepared by the reaction of adipic acid and acetic anhydride followed by catalytic depolymerization under vacuum. the ring-opening polymerization of (1) was investigated in the melt, and was studied as a function of polymerization temperature, time and concentration of catalyst (stannous 2-ethylhexanoate). from1H-NMR and IR spectra it can be deduced that stannous 2-ethylhexanoate coordinates with the anhydride bond of the ring, and that the resulting species reacts with the monomer by ring-opening of the acyl-oxygen bond. These observations indicate a non-ionic insertion polymerization mechanism at the beginning of the reaction, but after 2 h at 80°C, anhydride exchange appears to be the dominating reaction. Ring-opening melt polymerization of (1) resulted in low molecular weight poly (adipic anhydride).

ISSN:0022-233X    

DOI:10.1080/00222339009349564

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The graft copolymerization of 4-vinylpyridine was carried out on mercerized cellulose and partially carboxymethylated cellulose (PCMC) using eerie ammonium nitrate (CAN) as the initiator. the grafting parameters (grafting efficiency(GE), graft yield (G), and total conversion (C1)) were studied as a function of CAN concentration. It was shown that by increasing the CAN concentration,Gand C, reached a maximum. the graft yields for PCMC were significantly higher than those for mercerized cellulose. the largestGEvalues appeared for PCMC and mercerized cellulose at low and high CAN concentrations, respectively. the Ce(IV) consumption during grafting increased with rising concentration of CAN, and it was greater in the case of PCMC than of mercerized cellulose. After acid hydrolysis of the polysaccharide backbone, the average molecular weight of grafts was determined viscometrically. Molecular weight decreased with initiator concentration. Graft frequency(GF), on the other hand, increased with CAN concentration.GFfor PCMC was higher than that for mercerized cellulose. Ce(IV) consumption increased with CAN concentration and it was lower for mercerized cellulose than that consumed during grafting on PCMC. After that, the effect of CAN concentration on the graft copolymerization onto PCMC was examined while the total nitrate ion concentration was maintained constant at 1.59Mby addition of sodium nitrate. Maximum G, C1and Ce(IV) consumption were higher than in the previous case.

ISSN:0022-233X    

DOI:10.1080/00222339009349565

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The graft copolymerization of 4-vinylpyridine (4-VP) onto partially car-boxymethylated cotton (PCMC), having different carboxymethyl contents, was investigated. Under similar reaction conditions, both the graft yield and eerie ion consumption increased by increasing the degree of substitution of carboxymethyl groups of PCMC up to a value of 0.11, beyond which grafting and Ce(IV) consumption decreased. Proof for grafting onto PCMC was provided through IR analysis. the eerie salt-initiated polymerization of 4-VP in the absence of PCMC was also studied. Three series of homo-polymerization reactions of 4-VP directly initiated by eerie ammonium nitrate were carried out with varying reaction times. Each series was run at a different nitric acid concentration. Both conversion and eerie ion consumption, as well as molecular weight, increased with reaction time. Increasing the nitric acid concentration increased both conversion and eerie ion consumption while the molecular weight decreased.

ISSN:0022-233X    

DOI:10.1080/00222339009349566

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Persulfate-initiated grafting of crosslinked gelatin with acrylamide in aqueous medium is investigated. the high percentages of grafting are explained as a direct consequence of the heterophase nature of grafting. Optimum reaction conditions for a high percentage of grafting together with low homopoymer yields are discussed.

ISSN:0022-233X    

DOI:10.1080/00222339009349567

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The grafting of acyl chloride-capped polymers onto carbon black by the reaction of the acyl chloride group with the phenolic hydroxyl group on the surface was investigated. Acyl chloride-capped polymers were prepared by the reaction of functional polymers having terminal hydroxyl groups, such as poly(propylene glycol) (PPG), poly(ethylene glycol) (PEG), and silicone diol (SDO), with adipoyl dichloride or isophthaloyl dichloride. When acyl chloride-capped PPG (PPG-COCL) ([Mbar]n= 2.4 × 103) was reacted with carbon black, PPG was grafted onto the surface: the percentage of grafting reached to 27.7%. on the contrary, the reaction of PPG-COC1 with carbon black treated with diazomethane was scarcely observed. the PPG grafted onto carbon black was largely removed by hydrolysis with a dilute methanol solution of KOH. Based on these results, it was concluded that PPG grafted onto the surface with ester bonds. the percentage of grafting increased with an increase in the molecular weight of PPG-COC1. in addition, it was found that carbon black containing amino and imidazoline groups has high reactivity with PPG-COC1 and gives PPG-grafted carbon black with a high percentage of grafting. PPG-grafted carbon black produced a stable colloidal dispersion in organic solvents.

ISSN:0022-233X    

DOI:10.1080/00222339009349568

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The microphase structure of single polyurethane (PU) and acrylate networks as well as sequential interpenetrating polymer networks (IPNs), produced by the forming of a PU network in the presence of monomers of a penetrating network, was studied by small- and wide-angle x-ray analysis. It was established that each network component was of a two-phase structure consisting of disordered phase-separated microregions. the higher crosslink density of the acrylate network results in its higher heterogeneity. in IPNs, phase separation of a complex nature is realized: the PU matrix preserves some features of a single network structure, and the second component forms microregions 5-10 nm in size while retaining a certain level of interpenetra-tion of both network components. the microphase structure parameters of such systems are greatly dependent on the crosslink density of the penetrating network. This suggests the influence of a three-dimensional network of chemical bonds on the interdiffusion of branched fragments of the penetrating network and molecular chains of the matrix, one leading to the retardation of phase separation.

ISSN:0022-233X    

DOI:10.1080/00222339009349569

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Catalytic activity of a metal complex for both the transesterification of DMT (dimethyl terephthalate) and the polycondensation of BHET (bis(2-hy-droxyethyl terephthalate)) is described in terms of an acidity function formulated from the physical properties of the metal ion. Catalytic activity for both reactions is governed by the acidity of the metal ion, not by the type of anionic ligand. Maximum catalytic activity is observed with optimum bond strength between the metal ion and the double-bonded oxygen in the ester carbonyl group of DMT or BHET. Thus, a basic (less acidic) metal ion exhibits high catalytic activity for a more basic oxygen in the ester carbonyl of DMT, while a more acidic metal ions exhibits high catalytic activity for a less basic oxygen in the ester carbonyl of BHET. in the polycondensation reaction, a semiconductor metal ion shows higher activity than an insulator metal ion when compared at the same acidity value, but the former also catalyzes side reactions which can cause discoloration of the final polyethylene terephthalate) polymer. Discoloration is enhanced when a semiconductor metal ion has a redox couple during polycondensation.

ISSN:0022-233X    

DOI:10.1080/00222339009349570

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The copolymerization of polymethyl methacrylate (PMMA) macromer with butyl acrylate in benzene was studied. the PMMA macromer was obtained by radical polymerization in the presence of thioglycollic acid as a chain transfer agent, followed by termination with glycidyl methacrylate. the copolymerization rate and effects of various copolymerization conditions, such as molecular weight of macromer, charging ratio of macromer to monomer, amount of initiator, kind of solvent, concentration, and copolymerization temperature, on grafting efficiency and molecular weight of copolymer were investigated. the copolymers were purified by fractional precipitation. the purified copolymers with uniform PMMA grafts were characterized by GPC, IR, UV, and DSC. Structural parameters of the copolymers were determined by VPO and membrane osmometry. Average grafting number per chain decreases with an increase of conversion. Measurement of mechanical properties of the copolymers shows that both molecular weight and the content of the macromer affect mechanical properties of the copolymer, and within a certain range they behave like a thermoplastic elastomer.

ISSN:0022-233X    

DOI:10.1080/00222339009349571

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The thermal and hydrolytic stabilities at 90 and 120°C of butylN-phenyl urethane, N,N1-diphenylurea, butyl-α,γ-diphenyl allophanate, and 1,3,5-tri-phenylbiuret in 1,4-dioxane containing traces of water were investigated in the presence of dibutyltin dilaurate by HPLC. the stabilities decrease with increasing temperature and are also affected by the presence of water in the system. the rate and equilibrium constants of allophanate and biuret were calculated.

ISSN:0022-233X    

DOI:10.1080/00222339009349572

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor