The thermal degradation of poly(di-n-propyl itaconate) and poly(di-iso-propyl itaconate) G. Bos ˇkovic ´, L. Katsikas, J.S. Velic ˇkovic ´, I.G. Popovic ´ * Department of Organic Chemistry and Technology, Faculty of Technology and Metallurgy, Belgrade University, Karnegijeva 4/V, P.O.B. 494, YU-11001 Belgrade, Yugoslavia Received 15 June 1999; received in revised form 30 September 1999; accepted 20 October 1999 Abstract The non-oxidative thermal degradation mechanism of poly(di-n-propyl-) (PDnPI) and poly(di-iso-propyl itaconate) (PDiPI) were inves- tigated and compared to the structurally similar polymethacrylates. Analogous to the corresponding polymethacrylates, PDnPI thermally decomposes predominantly by depolymerisation, whereas a considerable amount of side chain scission occurs during the thermal degrada- tion of PDiPI. The thus formed carboxyl groups decarboxylate at elevated temperatures forming a carbonaceous residue.  2000 Elsevier Science Ltd. All rights reserved. Keywords: Thermal degradation; Poly(di-n-propyl itaconate); Poly(di-iso-propyl itaconate) 1. Introduction The thermal degradation of alkyl esters of poly- (methacrylic acid) has been extensively studied, especially by Grassie and coworkers [1,2]. However, after an initial paper [3] on the thermal degradation of polymers of di-n- alkyl esters of itaconic acid, only recently have details of the kinetics [4] and mechanisms [5,6] been published. All these studies were limited to n-alkyl esters. The kinetics of the thermal degradation of isomeric poly(dipropyl itaconate)s, poly(di-n-propyl-) (PDnPI) and poly(di-iso-propyl itaco- nate) (PDiPI) and of isomeric poly(dibutyl itaconate)s, poly(di-n-butyl-) (PDnBI), poly(di-iso-butyl-) (PDiBI) and poly(di-sec-butyl itaconate) have recently been reported [7]. The results obtained in this paper indicated that the mechan- isms of thermal degradation of these polymers are different. In the present paper, details of the mechanism of the thermal degradation of PDnPI and PDiPI, the structures of which are given below, will be presented. 2. Experimental section 2.1. Chemicals Di-n-propyl itaconate (DnPI) and di-iso-propyl itaconate (DiPI) were prepared by the standard acid-catalysed esteri- fication of itaconic acid with 1-propanol and 2-propanol, respectively. The formed water was azeotropically removed from the system. Due to the high solubility of 2-propanol in water it was necessary to add excess alcohol in this case. After the normal work-up procedure, the monomers were vacuum distilled immediately prior to polymerisation. GC analysis indicated that the purity of the monomers was greater than 99%. 2.2. Method of polymerisation Polymerisation was performed at 40°C in glass ampoules sealed under high vacuum using 0.5 mol% a,a 0 -isobisiso- butyronitrile (AIBN) as initiator. The yields were kept to below 10% to ensure relatively narrow molar mass distribu- tions. The polymers were isolated by precipitation with methanol containing about 5% water and made free of residual monomer by repeated precipitation from benzene Polymer 41 (2000) 5769–5775 JPOL 4506 0032-3861/00/$ - see front matter  2000 Elsevier Science Ltd. All rights reserved. PII: S0032-3861(99)00804-6 * Corresponding author. PDiPI PDnPI n n CH 2 C C O CH 2 C O O CH CH 3 CH 3 O CH CH 3 CH 3 CH 2 C C O CH 2 C O O H O CH 2 CH 2 CH 3 CH 2 CH 2 CH 3