Polystyrene resins with varied particle sizes (35 to 350-600 mu m) and pore diameters (300-1000 angstrom) were employed to study the effects of immobilization resin particle size and pore diameter on Candida antarctica Lipase B (CALB) loading, distribution within resins, fraction of active sites, and catalytic properties for polyester synthesis. CALB adsorbed rapidly (saturation time <= 4 min) for particle sizes <= 120 mu m (pore size = 300 angstrom). Infrared microspectroscopy showed that CALB forms protein loading fronts regardless of resin particle size at similar enzyme loadings (similar to 8%). From the IR images, the fractions of total surface area available to the enzyme are 21, 33, 35, 37, and 88% for particle sizes 350-600, 120, 75, 35 mu m (pore size 300 angstrom), and 35 mu m (pore size 1000 angstrom), respectively. Titration with methyl p-nitrophenyl n-hexylphosphate (MNPHP) showed that the fraction of active CALB molecules adsorbed onto resins was similar to 60%. The fraction of active CALB molecules was invariable as a function of resin particle and pore size. At similar to 8% (w/w) CALB loading, by increasing the immobilization support pore diameter from 300 to 1000 A, the turnover frequency (TOF) of epsilon-caprolactone (epsilon-CL) to polyester increased from 12.4 to 28.2 s(-1). However, the epsilon-CL conversion rate was not influenced by changes in resin particle size. Similar trends were observed for condensation polymerizations between 1,8-octanediol and adipic acid. The results herein are compared to those obtained with a similar series of methyl methacrylate resins, where variations in particle size largely affected CALB distribution within resins and catalyst activity for polyester synthesis.