Comparison of thermomechanical properties of statistical, gradient and block copolymers of isobornyl acrylate and n-butyl acrylate with various acrylate homopolymers Wojciech Jakubowski a , Azhar Juhari b , Andreas Best b , Kaloian Koynov b , Tadeusz Pakula b,1 , Krzysztof Matyjaszewski a, * a Center for Macromolecular Engineering, Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, PA 15213, USA b Max-Planck-Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany Received 12 December 2007; received in revised form 12 January 2008; accepted 17 January 2008 Available online 29 January 2008 Abstract Well-defined statistical, gradient and block copolymers consisting of isobornyl acrylate (IBA) and n-butyl acrylate (nBA) were synthesized via atom transfer radical polymerization (ATRP). To investigate structureeproperty correlation, copolymers were prepared with systematically varied molecular weights and compositions. Thermomechanical properties of synthesized materials were analyzed via differential scanning calorimetry (DSC), dynamic mechanical analyses (DMA) and small-angle X-ray scattering (SAXS). Glass transition temperature (T g ) of the resulting statistical poly(isobornyl acrylate-co-n-butyl acrylate) (P(IBA-co-nBA)) copolymers was tuned by changing the monomer feed. This way, it was possible to generate materials which can mimic thermal behavior of several homopolymers, such as poly(t-butyl acrylate) (PtBA), poly(methyl acrylate) (PMA), poly(ethyl acrylate) (PEA) and poly(n-propyl acrylate) (PPA). Although statistical copolymers had the same thermal properties as their homopolymer equivalents, DMA measurements revealed that they are much softer materials. While statistical copolymers showed a single T g , block copolymers showed two T g s and DSC thermogram for the gradient copolymer indicated a single, but very broad, glass transition. The mechanical properties of block and gradient copolymers were compared to the statistical copolymers with the same IBA/nBA composition. Ó 2008 Elsevier Ltd. All rights reserved. Keywords: Atom transfer radical polymerization (ATRP); Block copolymer; Gradient copolymer 1. Introduction The constantly advancing technologies demand new, high performance and more specialized materials with highly spe- cialized functions [1e9]. Such materials are no longer one (monolithic) component systems. Thus, the investigation on systems built with two or more components is in demand, especially for structureeproperty correlations. One example of a two-component system is block copolymer, in which the instantaneous composition changes discontinuously and abruptly along the chain. Another example is a gradient copoly- mer, in which instantaneous composition varies continuously along the chain contour. Both these copolymers are synthe- sized by controlled/living polymerization techniques [10]. In contrast to block and gradient copolymers, statistical copoly- mer composition is constant along the polymer chain. These three copolymers, even if built with the same type and number of units, may have completely different properties. Controlled/living radical polymerization (CRP) technology was developed in mid 1990s and can be applied to the prepa- ration of many different (co)polymers [11,12]. These CRP processes, such us atom transfer radical polymerization (ATRP) [13e15], nitroxide mediated polymerization (NMP) [16,17], or reversible additionefragmentation chain transfer (RAFT) [18] can be conducted at convenient temperatures, * Corresponding author. Tel.: þ1 412 268 3209; fax: þ1 412 268 6897. E-mail address: km3b@andrew.cmu.edu (K. Matyjaszewski). 1 Deceased on 06.07.2005. 0032-3861/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.polymer.2008.01.047 Available online at www.sciencedirect.com Polymer 49 (2008) 1567e1578 www.elsevier.com/locate/polymer