New evidences of the degradation mechanism of poly(oxy-1-chloromethylethylene) with basic reagents: studies with poly(oxy-1-chloromethyl-ethylene- co-oxyethylene) M. Pe ´rez, J.A. Reina, A. Serra, J.C. Ronda * Departament de Q. Analı ´tica i Q. Orga `nica. Universitat Rovira i Virgili, Plac ¸a Imperial Ta `rraco 1, E-43005 Tarragona, Spain Received 28 November 1999; received in revised form 14 January 2000; accepted 25 January 2000 Abstract This is an extension of our previous work on mechanistic studies of the degradation of the main chain during the chemical modification of poly(oxy-1-chloromethylethylene) (PECH) with phenolate to similar studies on the modification of poly(oxy-1-chloromethylethylene- co- oxyethylene) (PECH–PEO) with the same reagent. This polymer has been chemically modified with phenolate in the presence of a quaternary ammonium salt, i.e. tetrabutylammonium bromide (TBAB). Several reaction conditions were tested to provide the highest modification degrees with the minimum main-chain cleavage. The substitution of chlorine by phenolate was found to be accompanied by elimination reactions that led to vinylether moieties. The 13 C NMR technique was used to identify the different terminal groups arising from this cleavage. The nature of these groups confirmed that cleavage was caused by nucleophilic attack on the units neighbouring vinylic ones, mainly on the V V dyads. The results are consistent with those obtained from the modification reaction of poly(oxy-1-chloromethylethylene) (PECH) with phenolate.  2000 Elsevier Science Ltd. All rights reserved. Keywords: Degradation mechanism; Poly(oxy-1-chloromethyl-ethylene-co-oxyethylene); 13 C NMR 1. Introduction Chlorine-containing polymers are suitable starting mate- rials for synthesizing new functional polymers with a wide range of applications. Poly(vinyl chloride) (PVC) [1], poly- (chloromethylstyrene) (PCMS) [2], poly(oxy-1-chloro- methylethylene) (PECH) [3,4] and its copolymer with ethylene oxide (PECH–PEO) [5] are particularly interesting because they are commercially available and have chlorine atoms which can be nucleophilically substituted. The effec- tiveness of this kind of process is greater when chlorine is not directly attached to the main chain. Polymers containing chloromethyl units are therefore among the most promising starting materials for synthesizing functional polymers. In previous papers we studied the chemical modification of PECH with phenolate to find reaction conditions to produce highly modified polymers and reduce side- reactions like backbone degradation. On the basis of the end-groups detected by NMR spectroscopy, we proposed a mechanism to explain the degradative scission of the main chain [6]. Moreover, we accurately characterized the microstructure of the modified polymer, paying particular attention to the comonomer distribution, to see whether the statistics of the modification reaction depend on the chemi- cal microenvironment [7]. This paper aims to modify the 1:1 PECH–PEO copoly- mer with phenolate to investigate further the degradative scission observed in PECH, since the presence of ethylene oxide units may provide additional information to confirm the postulated mechanism. Moreover, modifying the PECH–PEO copolymer must lead to polymers with a flex- ible and polar backbone and with lower proportion of aromatic rings than the modified PECH homopolymer. These polymers could be used, when conveniently cross- linked and functionalized, as solid supports for synthesizing compound libraries for biological screening by the combi- natorial technique [8] or as polymeric reagents, catalysts or chromatographic stationary phases [2]. 2. Experimental section 2.1. Materials Hexane was dried by refluxing over CaH 2 and distilled Polymer 41 (2000) 7331–7337 0032-3861/00/$ - see front matter  2000 Elsevier Science Ltd. All rights reserved. PII: S0032-3861(00)00081-1 * Corresponding author. E-mail address: ronda@quimica.urv.es (J.C. Ronda).