Shashi D. Baruah

Styrene-maleic anhydride copolymers: Synthesis, characterization, and thermal properties

Radical copolymerization of styrene and maleic anhydride have been carried out in N, N-dimethylformamide at 60°C using 2,2′-azobisisobutyronitrile as initiator. The copolymer compositions were determined using an aqueous conductometric direct titration method. Monomer reactivity ratios were calculated by Fineman-Ross, Kelen-Tudos, and conversion-based Kelen-Tudos methods. Gel permeation chromatography was used to determine molecular weights and polydispersity indexes. The thermal degradation and energy of activation of the degradation process were determined by several thermogravimetric analysis and differential scanning calorimetric models. The thermal degradation of the copolymer is a two-stage process, the major degradation being the second stage. The copolymer degrades at a lower temperature than polystyrene.

Polymerization of methyl methacrylate by charge-transfer mechanism with 2,2'-bipyridine and iron(III) complex

Polymerization of methyl methacrylate (MMA) by the charge-transfer complex formed by the interaction of 2,2′-bipyridine (bpy), MMA, and carbon tetrachloride (CCl4) was studied in dimethylsulfoxide (DMSO) at 60°C. The rate of polymerization (Rp) is sensitive to the [CCl4] at low concentration of CCl4, but at a higher concentration it is practically independent of [CCl4]. Rp is proportional to [MMA]1.45±0.04 and [bpy]0.52±0.04 when [CCl4] > [bpy], and the average rate constant, k, at 60°C for the polymerization of MMA was 7.14 ± 0.40 × 10−6 L mol−1s−1. Kinetic studies showed that the polymerization proceeds through free radical intermediates. This article also reports the polymerization of MMA initiated by bpy and CCl4 and accelerated by Lewis acid, hexakis (dimethylsulfoxide)iron(III) perchlorate [Fe(DMSO)6](ClO4)3 at 60°C. The glass transition temperature and molecular weights of the samples were investigated by using differential scanning calorimetry and gel permeation chromatography techniques, respectively. Probable reaction mechanisms are proposed to explain the observed results.

Polymerization of methyl methacrylate by imidazole–carbon tetrachloride charge‐transfer system

The kinetics of charge-transfer (CT) polymerization of methyl methacrylate (MMA) in the presence of imidazole (Imy) and CCl 4 was studied in dimethyl sulfoxide (DMSO) at 60°C. The rate of polymerization (R p ) is sensitive to the [CCl 4 ] up to a concentration of 0.60 mol L -1 , but at a higher concentration, it is practically independent of the [CCl 4 ]. When [CCl 4 ] > [Imy], R p is proportional to [MMA] 1.45±0.15 and [Imy] 0.53±0.04 and the average rate constant for the polymerization of MMA is 3.25 ± 0.41 x 10 -6 L mol -1 s -1 . This article also reports the polymerization of MMA initiated by Imy and CCl 4 and accelerated by hexakis(dimethyl sulfoxide) iron(III) perchlorate, [Fe(DMSO) 6 ] (ClO 4 ) 3 (A), at 60°C. The presence of Fe(Imy) 3 3+ in the polymerization system produced well-defined induction periods. The rate constant at 60°C for the interaction of the poly(MMA) radical toward Fe(Imy) 3 3+ is 7.19 x 10 4 L mol -1 s -1 . A probable reaction mechanism for the polymerization system has been postulated to explain the observed results.

Photoinitiation of methyl methacrylate with a novel iron(III) oxalato complex

SummaryThe photopolymerization of methyl methacrylate (MMA) by the photoinitiator iron (III) tris (oxalato) ferrate(III) tetrahydrate, Fe[Fe(C2O4)3] . 4H2O (A) has been studied under UV radiation of 254 nm at 35°C in DMSO. The initial rate of polymerization, Rp is proportional to [MMA]1.11±0.13. Rp also varies linearly with the square root of [A] up to 5.00 X 10-4 mol l-1 and above this concentration, Rp decreases with the increase of [A]. It is likely that at a higher concentration of the complex A, the termination of the polymer chain occurs through interaction between the molecules of the complex. A suitable mechanism has been proposed to explain the kinetics of the reaction.