Vinyl Polymerization. 418. Polymerization of Vinyl Monomer Initiated by Betaine-Type Polymers in Aqueous Solution

Abstract

Three kinds of betaine-type polymers, which are macromolecular amphoteric electrolytes, were found to be able to polymerize vinyl monomers in aqueous solution through a radical mechanism without any further initiator. Betain-type polymers form hydrophobic areas (HA) in water. Vinyl polymerization commenced in the HA. The effect of the pH of the aqueous solution on polymerization was investigated.     

Vinyl Polymerization. 431. Vinyl Polymerizations Initiated by Block and Random Poly(Styrene-co-Sodium Methacrylate)

Abstract

The polymerization of some kinds of vinyl monomer was found to occur without an ordinary initiator in aqueous solutions of AB-type block or random copolymers of sodium methacrylate with styrene as a so-called “uncatalyzed polymerization.” Although the spin trapping technique showed that the initiation mechanism by the block copolymer was the same as that by the random copolymer, the initiating ability of the block copolymer was lower than that of the random copolymer. Such results are attributable to the difference in the incorporating ability of monomer into the micelles formed by the block copolymer and into the hydrophobic areas formed by the random copolymer.     

Design of Chitosan-5Fu Conjugate Exhibiting Antitumor Activity

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     

Enzyme and Nonenzyme Hydrolyses of End Ester Group in Polyethylene Glycol Esters

The enzyme and nonenzyme hydrolyses of the end ester group in polyethylene glycol (PEG) esters were studied. The end monoester in PEG ester is known to be easily hydrolyzed by alkaline or acidic solution. 2-Methyl-ω-benzoyloxypoly(oxy-1,2-ethanediyl)(Bz-PEG) and 2-methyl-ω-4-nitrobenzoyloxypoly(oxy-1,2-ethanediyl) were found to be hydrolyzed by lipase and esterase in Tris buffer solution (pH 7.7) but 2-methyl-ω-acetoxypoly(oxy-1,2-ethanediyl) was not. The parameters of enzyme reaction in the hydrolysis of ester bonds in Bz-PEG by esterase were estimated to be as follows: V_max = 6.09 × 10^?7 mol/dm^3.s, K_m = 7.63 × 10^?4 mol/dm³.     

Cyclic Acetal-Photosensitized Polymerization. 9. Photopolymerization of Triallylidene Sorbitol

Abstract

The photopolymerization of triallylidene sorbitol (TAS) was carried out in benzene at 40°C without the usual initiator. The polymerization of TAS was found to be initiated with the ester radical generated via the acetal radical from TAS by means of photoirradiation. The rate of polymerization and the molecular weight of polymer were small due to the degradative chain transfer, It was kinetically investigated from the standpoints of the degradative chain transfer by the allylidene group and the cyclization by three double bonds. The following results were obtained: (1) The relation between the rate of polymerization, R_p, the monomer concentration, [M], could be expressed by [M] /R_p = (A[M] + B)/(3[M] + C), where A, B, and C were constant; (2) the ratio of the rate constant of unimolecular cyclization to the total rate constant of bimolecular propagation and the chain transfer of uncyclized radical was estimated to be 3.0 mol/dm³. A small amount of cyclopolymerization took place.     

Vinyl Polymerization. 386. Polymerization of Methyl Methacrylate Initiated by Imidazole in Aqueous Solution of Copper(II) Chloride

The radical polymerization of methyl methacrylate (MMA) was carried out with the system of imidazole (Im), copper(n) chloride, and water at 85°C. The effects of the amount of each component on the conversion of MMA were investigated. The polymerization proceeded through a radical mechanism. The overall activation energy was estimated to be 28.7 kJ/mole. The conversion of MMA showed a maximum at pH 8-9 of the aqueous solution. The formation of a complex of CuCl₂ with Im, water, and MMA was confirmed by electronic spectra. An initiation mechanism was proposed.     

Synthesis and Cytotoxic Activity of Oxidized Galactomannan/ADR Conjugate

Abstract

Many polysaccharides are expected to apply as biomaterials because they generally show good biocompatibilities and biodegradabilities. It has recently been reported that the saccharides play important roles in biological recognition and the transmission of biological information on a cellar surface. Galactomannan (GalM) is a polysaccharide whose main chain is composed of β-1,4-linked mannose units only. It has some branching α-galactose residues at the C-6 position of mannose units. Therefore, it was of interest of us to use GalM as a drug carrier which was targeted to hepatocyte having a galactose receptor on its cellar surface. Dicarboxy-galactomannan (DC-GalM), which has reactive functional groups and is a carboxylic acid derivative of galactomannan, was prepared by IO^4-/CIO^2- oxidation of GalM. The obtained DC-GalM showed specific binding with maclura pomifera (MPA) [1] which has a specificity to α-galactose. Moreover, DC-GalM showed selective incorporation into hepatocyte. Adriamycine (ADR), which is one of the most prominent anticancer agents, was immobilized to DC-GalM. The DC-GalM/ADR conjugate showed specific cytotoxic activity against HepG2 human hepatoma cells which have a galactose receptor on the cell surface, compared with Hela utrocervical carcinoma cells which have no galactose receptor.     

Vinyl Polymerization. 439. Vinyl Polymerization Initiated by Poly(Ethylene Glycol] Diglycolic Acid or its Sodium Salt

Abstract

The polymerization of some kinds of vinyl monomer was found to occur in aqueous solutions of poly(ethylene glycol) diglycolic acid (PEG Acid) or sodium poly(ethylene glycol) diglycolate (PEG Acid Na) through radical mechanisms without any further initiator, as a so-called “uncatalyzed polymerization.” Although the initiating radical species for PEG Acid was determined to be the same as that for PEG Acid Na by means of the spin-trapping technique, the initiating ability of PEG Acid was higher than that of PEG Acid Na. These results are assumed to be attributable to the difference in the initiation mechanisms of the two systems and in the incorporating abilities of monomer into the hydrophobic areas formed by PEG Acid and PEG Acid Na.