Peo-based Abc Type Amphiphilic Triblock Copolymers

Design and synthesis of amphiphilic copolymer with complex architecture are always pursued by polymer chemists in past decades. Thanks to the development of living polymerization, combining the living radical polymerization with ionic polymerization, some linear and nonlinear (such as comb-like, star, dendritic, hyperbranch) copolymers are synthesized.Amphiphilic and functional ABC triblock copolymers have attracted more interests in the last decades for their widely application in self-assembly field. Among their different components poly(ethylene oxide)(PEO) was the most familiar, due to its outstanding properties such as biocompatibility, crystallizability and well dissolvability in water and most organic solvent. That's why PEO was always considered as one of the blocks when scientists design new ABC triblock copolymers.On the other hand, for the amphiphilic multiblock copolymers, the synthesis is solely confined in polycondesation of prepolymers. It is still a challenge to explore a simple and effective way to synthesize these copolymers via living polymerization. Herein, we have synthesized different ABC triblock copolymers by the combination of different living polymerization, and study the effect on the properties of triblock copolymers with PEO as different position, and this was rarely investigated. In this paper, the triblock copolymers mPEO-b-PCL-b-PS and PS-b-PEO-b-PCL with PEO as different position were successfully synthesized by the combination of living anionic polymerization, coordination-insertion ring-opening polymerization, atom transfer radical polymerization, and nitroxide-mediated radical polymerization. The main results have been obtained as follows:1. The ABC amphiphilic triblock copolymers mPEO-b-PCL-b-PS was designed and synthesized. The EO was polymerized by living anionic polymerization using di(ethylene glycol) potassium as initiator, theα-methoxy poly(ethylene oxide) (mPEO) was obtained. The mPEO was served as macroinitiator to initiate the polymerization ofε-caprolactone by coordination-insertion ring-opening polymer- ization using stannous octoate (Sn(Oct)₂) as catalyst, and the diblock copolymers were obtained. Then the macroinitiator mPEO-b-PCL-Br for atom-transfer radical polymerization was obtained by 2-Bromoisobutyryl bromide reacting with the hydroxyl at the end of resultant diblock mPEO-b-PCL. Finally, the mPEO-b-PCL-Br was served to initiate the polymerization of styrene (St) by atom-transfer radical polymerization (ATRP) in the present of copper bromide and N,N,N',N'',N''-Pentamethyldiethylenetriamine(PMDETA), and the desired triblock copolymers mPEO-b-PCL-b-PS were obtained. The investigation of kinetics of the polymerization of styrene confirmed that the polymerization was under control. The desired triblock copolymer and its intermediates were characterized.2. The ABC amphiphilic triblock copolymers PS-b-PEO-b-PCL was designed and synthesized. Firstly, the EO was polymerized by living anionic polymerization using 4-hydroxyl-2,2,6,6-tetramethylpiperidinyl-1 -oxy and diphenylmethyl-potassium (DPMK) as initiator, and the TEMPO-PEO with 2,2,6,6-tetramethylpiperidinyl-1-oxy(TEMPO) and hydroxyl end group was obtained. The TEMPO radical in TEMPO-PEO acted as a radical trapper to mediate the polymerization of styrene (St) by nitroxide-mediated radical polymerization (NMP) using benzoyl peroxide (BPO) as initiator, and the diblock copolymers were obtained. Finally, The PS-b-PEO was served as macroinitiator to initiate the polymerization ofε-caprolactone by coordination-insertion ring-opening polymerization using stannous octoate (Sn(Oct)₂) as catalyst, and the desired triblock copolymers PS-b-PEO-b-PCL were obtained. The desired triblock copolymer and its intermediates were characterized.The position of each block of multiblock copolymers have effect for properties of multiblock copolymers. It was confirmed that the PEO block position have effect on T_g and T_m of each block of ABC amphiphilic triblock copolymers mPEO-b-PCL-b-PS and PS-b-PEO-b-PCL by DSC.