Ideal tetrafunctional amphiphilic PEG/PDMS conetworks by a dual-purpose extender/crosslinker. I. Synthesis

The synthesis of a new type of amphiphilic conetwork (APCN) consisting of well-defined hydrophilic poly(ethylene glycol) (PEG) and hydrophobic polydimethylsiloxane (PDMS) segments is described. The conetwork is ideal (the lengths of each PEG and PDMS chain segments, respectively, are identical) and tetrafunctional (exactly four chains emanate from each crosslink site). The synthesis of the conetworks was achieved by the use of a novel dual-purpose extender/crosslinker Y (his [(dimethylsilyl)oxyl-[(etoxydimethylsilyl)oxy]phenylsilane, (SiPh(SiH)(2)OEt)), in two steps: (1) Synthesis of a new linear random multiblock copolymer (MBC) (AY)(n)(BY)(m), where A is the hydrophilic PEG and B is the hydrophobic segment, and (2) Crosslinking the multiblocks by catalytic condensation of the SiOEt groups in the Y units. The extender/crosslinker fulfills two totally different functions: First, it extends two incompatible hydrophilic and hydrophobic prepolymers (PEG and PDMS) to a random MBC, and, subsequently, it crosslinks the multiblocks to the target APCN. The synthesis and characterization of the extender/crosslinker is also presented. (c) 2005 Wiley Periodicals, Inc.