摘要:

Physical characterization of the products resulting from condensation of xylan with organostannanes halides is consistent with a tin-modified product. Results from elemental analysis shows the presence of tin consistent with the presence of the tin moiety. Results from control reactions are consistent with the product containing portions derived from both reactants. The presence of the Sn–O–R ether linkage is found by infrared spectroscopy. The presence of portions derived from both reactants is indicated by mass and infrared spectral results.

ISSN:0022-233X    

DOI:10.1080/00222338808052128

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The polymerization of α-methylstyrene catalyzed by a polymer-supported Lewis acid catalyst, polystyrene-gallium trichloride complex, is described. The kinetic equation of the cationic polymerization isRp= k˙Cms˙Ccat, and the apparent activation energy is 20.9 kJ/mol. The effect of different solvents on the polymerization rate is quite pronounced; for example, the polymerization rate decreased in the following order in the three solvents: CH2ClCH2Cl < CH2Cl2< CCl4. High molecular weight poly(α-methylstyrene) (Tg= 185°C) could be obtained at room temperature. The mechanism of the polymerization is also discussed.

ISSN:0022-233X    

DOI:10.1080/00222338808052129

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

A polymer pearl carrier, diphenylaminomethylpolystyrene, was synthesized by the reaction of chloromethylated polystyrene beads (4% DVB) with diphenylamine and was combined with titanium tetrachloride in chloroform to form a very stable complex containing 24.38% Cl (equivalent to 1.72 mmol TiCl4/g complex beads). The complex showed good catalytic activity in organic reactions such as esterification, acetalation, and ketal formation. The catalyst can be reused at least eight times without losing its activity.

ISSN:0022-233X    

DOI:10.1080/00222338808052130

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The structure, course of the reaction, and molecular weight distribution for resorcinol-crotonaldehyde resins were determined by HET2DJ13C NMR,1H NMR, and GPC. In the first step of the reaction, the free reactive Positions 4 and 6 of resorcinol react with crotonaldehyde. Due to steric hindrance, Position 2 is less reactive in spite of its high electron density. In the next step, addition products react with themselves or monomers to form higher products. Water is eliminated during the reaction. The final molecular weight of the resins is up to 10 000.

ISSN:0022-233X    

DOI:10.1080/00222338808052131

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Redox-initiated free-radical cyclopolymerization of the nonconjugated divinyl monomerN,N′-methylenebisacrylamide was studied at 25–40°C, involving trisacetatomanganese(III) dihydrate as oxidant with four different reductants, methyl ethyl ketone (2-butanone), cyanoacetic acid, malic acid, and thiomalic acid. While the general mechanistic sequence is the same, the modes of termination are different in these cases. Because the reactivities of the different free radicals from the four redox pairs are different, the kinetic order with respect to the monomer, oxidant, and reductant differ considerably in magnitude. The kinetic and thermodynamic parameters were calculated.

ISSN:0022-233X    

DOI:10.1080/00222338808052132

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Water-soluble 2,3-dihydroxypropylcellulose (DHPC) was successfully synthesized by the reaction of 3-chloro-1,2-propanediol with alkali cellulose in dioxane, or with glycidol in acetone. DHPC from the glycidol reaction was shown to have better solubility and yield. DHPC made from cotton wool and glycidol possesses the highest intrinsic visocisty (up to 4.05 dL/g). Quantitative13C-NMR analysis was utilized to estimate the molar substitution and degree of substitution of the resulting DHPC. Since the ratios of molar substitution to degree of substitution were found to be 2 or less, the substituents on the cellulose probably consist of monomer, dimer, or trimer of the alkylation agents used. Above the critical concentration of DHPC, the solution viscosity was found to be increased tremendously upon treating with boric acid under basic conditions.

ISSN:0022-233X    

DOI:10.1080/00222338808052133

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Water-soluble 2,3-dihydroxypropylcellulose-polyacrylamide graft copolymers (DHPC-g-PAM) were prepared by Ce4+ion-initiated graft copolymerization of acrylamide (AM) onto 2,3-dihydroxypropylcellulose (DHPC) dissolved in dilute nitric acid at room temperature under argon. The ratios of the concentration of Ce4+ion to the concentration of DHPC were shown to affect the number and the length of the polyacrylamide grafts. The average number of grafts per chain was determined by acid-catalyzed degradation of the cellulose backbone and was found to be consistent with the presence or absence of free DHPC in the polymerization product prior to hydrolysis. The average number of grafts per DHPC molecule was found to be 2.7 or less depending on the reaction conditions.

ISSN:0022-233X    

DOI:10.1080/00222338808052134

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

As a follow-up to earlier investigations into the high-pressure polymerization of ethylene with symmetrically substituted bifunctional peroxides, the suitability of 2,5-dimethylhexane-2-t-butylperoxy-5-perpivalate, a peroxide with different substituents on both O—O groups, has been tested. The polymerization tests were carried out in continuous operation in a stirred autoclave at 1700 bar, 240–285°C, a residence time of 60 s, and an initiator concentration of 3–25 mol ppm in the feed. Conversions of up to 30% were achieved. The specific initiator consumption was 0.2–1 g initiator per kg polyethylene. The density of the polymers obtained was 0.915–0.925 g/mL, their average molecular weight was 40 × 103to 60 × 103, and their melt flow index was 0.001–100 g/10 min. On the basis of the molecular weight distribution, polydispersities of 4–7 were obtained.

ISSN:0022-233X    

DOI:10.1080/00222338808052135

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Graft copolymers of poly(diallyldimethylammonium chloride), (poly-DADMAC), with acrylamide were synthesized using a ceric salt/nitric acid initiation system. The effects of concentration of initiator, monomer, and substrates were studied. Copolymers were characterized by viscometry and size-exclusion chromatography. The highest molecular weight (Mw) of graft copolymer obtained was 1.70 × 106. The compositions of copolymers are dependent upon the ratios of the concentration of monomer to the concentration of substrate. The highest content of DADMAC monomer unit in the copolymer was 33 wt%.

ISSN:0022-233X    

DOI:10.1080/00222338808052136

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The polymerizable derivatives of chloramphenicol were prepared and free-radical copolymerized with acrylamide, methacrylic acid, and 2-(dimethylamino)ethyl methacrylate in order to obtain polymers with pharmacological activity. The monomeric and polymeric derivatives were subjected to antibacterial activity tests againstBacillus polymyxa.

ISSN:0022-233X    

DOI:10.1080/00222338808052137

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor