Journal of Chromatography A, 910 (2001) 51–60 www.elsevier.com / locate / chroma Characterization of polystyrene and polyisoprene by normal-phase temperature gradient interaction chromatography * Wonmok Lee, Donghyun Cho, Byung Ok Chun, Taihyun Chang , Moonhor Ree Department of Chemistry and Center for Integrated Molecular Systems, Pohang University of Science and Technology, Pohang 790-784, South Korea Received 28 June 2000; received in revised form 6 November 2000; accepted 10 November 2000 Abstract Temperature gradient interaction chromatography (TGIC) is applied to the characterization of polyisoprene (PI) and polystyrene (PS) using normal-phase (NP) stationary phase – bare silica or diol bonded silica. Tetrahydrofuran–isooctane mixtures are used as a mobile phase. PI and linear and star shaped PS samples are successfully fractionated in terms of the molecular mass with a high resolution comparable to that of reversed-phase (RP) HPLC. Temperature dependence of the retention shows that the enthalpy of adsorption of PS to the stationary phase is exothermic. In addition, some characteristic features of the NP-TGIC system relative to those of RP-TGIC are presented, which include a high sensitivity on the polar end group and the simultaneous size-exclusion chromatographic and TGIC characterization of PS and PI mixtures.  2001 Elsevier Science B.V. All rights reserved. Keywords: Temperature gradient interaction chromatography; Polymers; Polystyrene; Polyisoprene 1. Introduction composition difference of copolymers, tacticity, and end-group difference. Furthermore, the resolution of By virtue of the recent development of liquid SEC is limited due to the band broadening effect and chromatography (LC), there has been significant it is often impossible to characterize the accurate progress on the fractionation of macromolecules. MWD of polymers with narrow MWD such as most Among numerous variations of LC methods, size- anionically polymerized polymers [4]. exclusion chromatography (SEC) has been the most For a couple of decades, reversed-phase liquid popular method for the characterization of molecular chromatography (RPLC) has been applied for the mass distribution (MWD) of synthetic and natural fractionation of high-molecular-mass polymers [5– polymers [1–3]. Nevertheless, since SEC separates 16]. RPLC exhibits a much higher resolution than the polymer molecules according to their size only, it SEC. Recently, Chang and co-workers have reported is not an efficient method to separate polymers in successful applications of the temperature gradient terms of chemical heterogeneity, such as chemical RPLC in the molecular mass distribution analysis of various polymers such as polystyrene (PS) [17–21], polyisoprene (PI) [22] and poly(methyl methacrylate) *Corresponding author. Tel.: 182-54-2792-109; fax: 182-54- (PMMA) [23]. In the separation technique named 2793-399. E-mail address: tc@postech.ac.kr (T. Chang). temperature gradient interaction chromatography 0021-9673 / 01 / $ – see front matter  2001 Elsevier Science B.V. All rights reserved. PII: S0021-9673(00)01163-8