Comparison of the effect of pore architecture and bead size on the extent of plasmachemical amine functionalisation of poly(styrene-co- divinylbenzene) permanently porous resins Jas Pal Badyal a , Audrey M. Cameron a , Neil R. Cameron a, * , Leslie J. Oates a , Gisle Øye a , Patrick G. Steel a , Benjamin G. Davis b , Diane M. Coe c , Richard A. Cox c a Department of Chemistry, University of Durham, South Road, Durham DH1 3LE, UK b Department of Chemistry, Dyson Perrins Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QY, UK c GlaxoSmithKline, Medicines Research Centre, Gunnels Wood Road, Stevenage SG1 2NY, UK Received 4 September 2003; received in revised form 23 January 2004; accepted 30 January 2004 Abstract Poly(styrene-co-divinylbenzene) (PS/DVB) permanently porous resins suitable for plasmachemical modification with allylamine were prepared by suspension polymerisation. Experimental design methods were employed to investigate simultaneously the influence of crosslinker content, porogen type and porogen level on the surface area, pore volume and pore diameter of the resins. From this, it was found that the porogen has a greater influence than the crosslinker. Variation of porogen type and level while keeping crosslinker level constant then lead to the maximisation of each parameter of interest, resulting in a set of samples with a wide range of values. Six samples were then chosen, representing high and low values of each property, and were subjected to plasmachemical modification with allylamine. It was found that pore volume had the greatest influence on the extent of modification. However, subsequent experiments indicated that the extent of modification is much greater for smaller beads. It is concluded that plasmachemical functionalisation occurs mainly on the external surface of the beads. q 2004 Elsevier Ltd. All rights reserved. Keywords: Polymer beads; Porous; Plasmachemistry 1. Introduction Permanently porous 1 polystyrene-co-divinylbenzene (PS/DVB) resins were invented in the 1950s and are widely used as ion-exchangers, polymeric absorbents, chromato- graphic separation media and as solid supports for organic synthesis [1]. They are now a well-known alternative to gel- type supports for a variety of applications, and in particular for solid-phase chemistry, in which their advantages have been confirmed by a number of groups [2]. Various applications of polymer supports in organic synthesis require careful design and control of the porous structure of the support [3]. Polymer beads with fixed pores can be obtained by suspension polymerisation, which is particu- larly suited to the production of large spherical beads typically in the range 5–1000 mm [4]. By careful choice of porogen (and crosslinker type/ concentration), a wide range of porosities can be produced (according to IUPAC definition [5]—micropores: , 20 A ˚ ; mesopores: between 20 and 500 A ˚ ; macropores: . 500 A ˚ ). The conditions for obtaining a permanently porous structure have been reviewed in great detail [3]. It has been established that the porosity and surface area of the beads are strongly influenced by the polymer synthesis conditions, including porogen composition, porogen concentration (degree of dilution), crosslinking degree and reaction temperature [6,7]. A high concentration of crosslinker is necessary to produce permanent porosity with a high surface area; materials prepared with insufficient crosslinker, even in the presence of a porogenic solvent, are essentially non- porous [3]. 0032-3861/$ - see front matter q 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.polymer.2004.01.072 Polymer 45 (2004) 2185–2192 www.elsevier.com/locate/polymer * Corresponding author. Tel.: þ 44-191-3342008; fax: þ 44-191- 3844737. E-mail address: n.r.cameron@durham.ac.uk (N.R. Cameron). 1 The term ‘macroporous’ is avoided as it implies pores of .50 nm in diameter.