Synthesis of anionic amphiphilic diblock copolymers of poly(styrene) and poly(acrylic acid) by reverse iodine transfer polymerization (RITP) in solution and emulsion

Abstract

offer the appealing prospect of synthesizing these amphiphilic block copolymers. However, there are numerous drawbacks arising from the use of each technique in terms of the high cost of the control agents as in NMP and RAFT, the cumbersome removal of the catalyst in the ATRP catalytic system and the instability problems of the transfer agents requiring thereby special precautions during storage. In the respect of overcoming the problems posed by the common CRP techniques, great interest is involved in adopting and developing the innovative CRP method called Reverse Iodine Transfer Polymerization (RITP) 7-8 which was developed by our group. This method comprises a degenerative chain transfer mechanism and its simplicity rests on the use of molecular iodine (or its precursors such as sodium iodide, NaI) 9-10 for the in situ generation of transfer agents. Herein, we report the synthesis of amphiphilic diblock copolymers of poly(styrene), (PS) and poly(acrylic acid) (PAA) from the easy cleavable tert-butyl acrylate precursor, by reverse iodine transfer polymerisation (RITP) in solution and emulsion. Experimental Materials. Tert-butyl acrylate (tBA, Aldrich, 98%) was extracted three times with 5% aqueous NaOH and then washed with distilled water. After drying over CaCl2 and filtering off the drying agent, the monomer was distilled under reduced pressure. Styrene (Acros, 99%) and toluene (BDH, 99%) were distilled under reduced pressure before use. 2,2'- Azobis(isobutyronitrile) (AIBN, Fluka, 98 %) was purified by recrystallization in methanol. Iodine (I2, Aldrich, 99.8%), trifluroacetic acid (TFA, Aldrich, 99%), dichloromethane (DCM) (Fluka), potassium persulfate (KPS, Aldrich, 99%), sodium 1-hexadecanesulfonate (M= 328.49 g.mol -1 , Lancaster, 99%), and Mersolat H40 (Lanxess, 40% aqueous solution) were used as received. Water was deionized by passing it through columns packed with ion exchange resins. Instrumentation. The samples were characterized by 1