摘要:

In order to provide a macromolecular prodrug of 5-fluorouracil (5FU) reducing the side effects, having an affinity for tumor cells, and exhibiting strong antitumor activity, the covalent attachments of 5FUs to chitosan and chitosamino-oligosaccharide (COS) through hexamethylene spacer groups via urea, urea bonds were carried out. The effect of prolongation of life was tested in vivo against p388 lyrnphocytic leukemia in female CDF, mice by intra-peritoneal (i.p.) transplantation/i.p. injection and the growth-inhibitory effect on Meth-A fibrosarcoma or MH-134Y heputoma was evaluated in vivo in SPF-C3H/He scl male or Balb/c male mice by subcutaneous (s.c.) implantation/intravenous (i.v.) injection. The effects of the degree of polymerization of chitosan and

ISSN:0022-233X    

DOI:10.1080/00222339108054077

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Alternating copolymers of α-methylstyrene (α-MeSt) and maleimide (MI) were prepared by free-radical initiated polymerization at different monomer-to-monomer concentrations in the feed in CHCl3, as solvent. The equilibrium constant of -MeSt and MI was determined by the transformed Benesi-Hildebrand NMR method in CDCl3, and has a value of 0.03 L/mol. From the equation Rp= Rp(f) + Rp(CT) proposed by Shirota and coworkers, Rpf) and RpCT) were calculated, and it was found that the copolymerization of -MeSt with MI proceeds predominantly through participation of the CT complex. Alternating copolymers have a glass transition temperature of 567 K (DSC method). Alternating copolymer decomposes via a one-step reaction at 350°C.

ISSN:0022-233X    

DOI:10.1080/00222339108054078

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Intrinsic viscosities and gel permeation chromatography (GPC) elution times were determined in toluene on commercially available standards of polystyrene (PSTY) and polymethyl methacrylate (PMMA) having Mnin the range of 103to 105and 104to 106, respectively. In addition, elution times were determined on the discrete GPC peaks of dimer, trimer, tetramer, etc. as seen in lower molecular weight PSTY and PMMA. Intrinsic viscosities of oligomers were estimated by extrapolation of the Mark-Houwind-Sakurada equations determined from our data, and the results were used to establish a universal calibration curve over a wide range of molecular weights. A similar approach was taken by using literature data for the intrinsic viscosities of PSTY and PMMA in tetra-hydrofuran. It was verified by proton NMR that the universal calibration curve so constructed is useful at Mn, values as low as 300. No correction was necessary for chain length dependence of the detector response.

ISSN:0022-233X    

DOI:10.1080/00222339108054079

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The dimethyl phenyl phosphine (DMPP) initiated polymerization of methyl methacrylate (MMA) in dimethylsulfoxide was studied. Polymerization of MMA in this system required the presence of transition metal ions like Fe3+or Cu2+. Kinetic studies showed that the propagation was free radical in nature. An interaction between DMPP and MMA was detected spectrophotometrically. A proposed mechanism involves a transition metal ion-activated dipole interaction between the carbonyl oxygen and the phosphorus atom with the ultimate formation of a methyl methacrylate type of free radical.

ISSN:0022-233X    

DOI:10.1080/00222339108054080

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

A series of linear polyurethaneureas was prepared by a two-step solution polymerization method. The prepolymer formed by the reaction of 4,4′-diphenyl methane diisocyanate with polyethylene glycol/polypropylene glycol was further chain extended with ethylene diamine/propane diamine/hexane diamine. The chemical shift values of various carbon species of the block copolymer were analyzed and assigned. The products formed due to the presence of water at different stages of polymerization were also characterized.

ISSN:0022-233X    

DOI:10.1080/00222339108054081

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Kinetic studies of the free radical copolymerization ofN-(2,4,6- tribromophenyl) maleimide (TBPMI) with styrene in solution were carried out. The thermal and flammability characteristics of the resulting polymers were also investigated. The monomer reactivity ratios were found to ber1= 0.006 ± 0.0026 (TBPMI) andr2= 0.086 ± 0.0023, and the activation energy of the copolymerization reaction was Ea= 73.6 kJ/mol. The resulting copolymers showed an alternating structure regardless to the monomer feed composition. The molecular weights of the copolymers obtained are relatively high and gradually increase by increasing the TBPMI fraction in the feed, whereas the Tg's showed similar values (540 K) for the equimolar ratio of the comonomers. The course of copolymerization up to high conversion was followed by microcalorimetry and is characterized by a remarkable increase of the initial reaction rate as the fraction of TBPMI was increased; it is also higher at higher total monomer concentrations. However, the overall conversion decreases when the fraction of TBPMI is higher than the equimolar ratio. The thermal stability of the alternating copolymers is higher than that of polystyrene, and their mixture showed appreciable flame-retardant properties, as demonstrated by a limiting oxygen index measurement.

ISSN:0022-233X    

DOI:10.1080/00222339108054082

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The kinetics of butadiene polymerization in hydrogenated gasoline was studied under Fe(naph)2–Al(i-Bu)3–CH2˭CHCH2Cl catalyst. The kinetic equation for the reaction was derived as

ISSN:0022-233X    

DOI:10.1080/00222339108054083

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

A new treatment to characterize copolymer composition in binary copolymerization systems was developed by using a steady-state assumption for free radicals. It gives a copolymer composition equation solely through classical kinetic theory with the antepenultimate effect taken into account. This equation and its derivation procedure are compared with those previously published.

ISSN:0022-233X    

DOI:10.1080/00222339108054084

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

ISSN:0022-233X    

DOI:10.1080/00222339108054076

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor