Polymer Communication Liquid induced crystallization of polyethylene naphthalate) oligomers N.R. James, C. Ramesh, S. Sivaram * Division of Polymer Chemistry, National Chemical Laboratory, Pune 411008, India Received 25 July 2001; received in revised form 1 October 2001; accepted 2 October 2001 Abstract Amorphous polyethylene naphthalate) PEN) oligomer has been crystallized at room temperature by treating in liquids having solubility parameter, d , in the range of 15±29 J cm 23 ) 1/2 . It has been observed that the liquids having d in the range of 18.5±25 are able to crystallize PEN oligomer ef®ciently. A direct correlation has been observed between d and crystallite size calculated from WAXS technique. q 2001 Elsevier Science Ltd. All rights reserved. Keywords: Crystallization; Polyethylene naphthalate); Solubility parameter 1. Introduction It is known that in the presence of certain interactive liquids, crystallization of amorphous polymers can occur at room temperature well below the glass transition tempera- tureofthepolymer.TheliquidinducedcrystallizationinPET has been studied in detail [1±4]. There are a few reports regarding liquid induced crystallization of high molecular weightPEN.Theliquidsmainlystudiedaredioxane,aniline, DMF and methylene chloride whose solubility parameters, d , are 20.42, 22.6±24.2, 24.9, 19.9 J cm 23 ) 1/2 , respectively. Solubility parameter of PEN is 20.31 J cm 23 ) 1/2 calculated by Synthia method) [5]. Kim et al. reported [6] that the samples treated in dioxane above 408C exhibited a-crystal- line form and a spherulitic texture, while crystallization at 258C gave b-crystalline form and an amoebae structure. DMF treated samples mainly showed a-crystalline form irrespective of the treatment temperature. But a trace of b-crystalline structure was observed in the sample treated at 108C. The b-crystal occurred at lower treatment tempera- ture in liquid induced crystallization while it occurred at higher crystallization temperatures in the case of thermal crystallization [7,8]. PEN could be crystallized in the presence of ethylene glycol or water under pressure at temperatures of 170 and 1608C [9]. Crystallization in this process cannot be treated as liquid induced as the solubility parameterofethyleneglycolis29.1±33.4andthatofwateris 48. In the present work, PEN oligomer is crystallized by liquids having a wide range of solubility parameters and the role of solubility parameter on crystallization is studied. The liquids used are diethylether 15.2±15.6), carbon tetra- chloride 17.7), ethylacetate 18.6), toluene 18.2±18.3), benzene 18.5±18.8), chloroform 18.9±19), dichloro- methane 19.9), acetone 20±20.5), ethanol 26.0±26.5) and methanol 29.2± 29.7). There has been no prior report on liquid induced crystallization of PEN oligomers. 2. Experimental 2.1. Preparation of oligomers The PEN oligomer was prepared by disproportionation of high molecular weight PEN. The PEN pellets and excess of ethylene glycol were taken in 1000 ml round bottom ¯ask. The temperature was raised to 1908C while the pellets were stirred thoroughly. The reaction was continued for 10 h. The residue was ®ltered and washed with hot water and methanol and dried at 808C for 12 h. The inherent viscosity of the sample was 0.18 dL g 21 and was measured at 258C in auto- mated Schott Gerate viscometer using Ubbelhode suspended level viscometer in 40/60 w/w), phenol/1,1 0 ,2,2 0 -tetra- chloroethane solvent mixture at a concentration of 0.5%. The oligomers were melted and quenched in liquid nitrogen to obtain amorphous materials. The DSC thermogram of these samples con®rmed the amorphous nature. 2.2. Crystallization The samples were crystallized at room temperature by stirring the oligomer in the liquids for about 12 h. Samples Polymer 43 2002) 1559±1561 0032-3861/02/$ - see front matter q 2001 Elsevier Science Ltd. All rights reserved. PII: S0032-386101)00675-9 www.elsevier.com/locate/polymer * Corresponding author. Tel.: 191-20-589-3234. E-mail address: sivaram@ems.ncl.res.in S. Sivaram).