Preparation of porous poly(styrene-co-divinylbenzene) monoliths with controlled pore size distributions initiated by stable free radicals and their pore surface functionalization by grafting

A stable free radical (SFR) mediated preparation of porous poly(styrene-co- divinylbenzene) monoliths using new types of SFRs and a novel binary poroge nic solvent consisting of poly(ethylene glycol) and 1-decanol has been stud ied. Polymerizations carried out in the presence of 3-carboxy-2,2,5,5-tetra methylpyrrolidinyl-1-oxy (3-carboxy-PROXYL) or 4-carboxy-2,2,6,6-tetramethy lpiperidinyl-1-oxy (4-carboxy-TEMPO) were faster, and higher degrees of mon omer conversions were achieved in a shorter period of time compared to the corresponding reactions mediated by 2,2,6,6 -tetramethylpiperidinyl-1-oxy ( TEMPO). The effect of the type of SFR (TEMPO, 3-carboxy-PROXYL, 4-carboxy-T EMPO, 4-amino-TEMPO, 4-acetamido-TEMPO, and 4-trimethylammonio-TEMPO iodide ) on the pore size distribution was also investigated. The use of carboxy f unctional SFRs simultaneously accelerated the reaction kinetics, improved t he permeability of the prepared monoliths, and enabled control of the porou s properties of the monolithic polymers over a wide range simply by modifyi ng the ratio of poly(ethylene glycol) 400 and 1-decanol in the porogenic mi xture. The reinitiation capability of poly(styrene-co-divinylbenzene) monol iths capped with 3-carboxy-PROXYL or 4-carboxy-TEMPO moieties was utilized to perform in situ grafting of 2-hydroxyethyl methacrylate and 3-sulfopropy l methacrylate, resulting in monoliths with altered surface polarities.