Preparation And Properties Of POSS-based Hybrid Star Poly(Phenyl Isocyanide)s

As one of the significant secondary structure in nature,the helix plays an essential role in the living system.Inspired by structures of biological helices,chemists have developed a wide variety of helical molecules,oligomers,polymers.Among them,polyisocyanides have attracted wide attention due to their unique rigid rod helical structure.In this work,POSS-NH₂ was synthesized from（3-aminopropyl）triethoxy siloxane by hydrolysis and shrinkage.Then it reacted with propargyl of 3-carboxylic propionate to introduce alkyne group into POSS.Finally,by reactioning with trans-bis（triethylphosphine）palladium（II）chloride,well-defined POSS-Pd（II）with polyhedral oligomeric silsesquioxane（POSS）core were designed and prepared in this contribution.The initiator with eight alkyne-Pd（II）complexes on the POSS core（POSS-Pd（II））was firstly synthesized.The complex was able to initiate the polymerization of phenyl isocyanide monomer in an active/controlled chain growth mode,and afforded well-defined starlike hybrid helical poly（phenyl isocyanide）s with POSS core.Meanwhile,polymerization of chiral phenyl isocyanides with decyl chain modified pendant L-or D-alanine afforded optically active hybrid starlike helical PPIs with preferred handedness.Such as the Molar CD(Δε₃₆₄)of POSS-poly-2L₁₀₀was 18.1 M^-1 cm^-1.What’s more,amphiphilic starlike hybrid helical poly（phenyl isocyanide）block copolymers presenting thermoresponse were easily obtained,and the self-assembly and thermo-responsive behaviours were studied.The LCST,CAC and average diameter of POSS-Poly(2L₂₀-b-3₈₀)was 63.8℃,73.1 mg/m L and 212 nm,respectively.In addition,cross-linked hybrid helical PPIs were obtained via the transesterification reaction between pentafluorophenyl ester and cystamine.Benefitting from the essential chirality of the handed helical PPIs,the cross-linked hybrid PPIs showed excellent ability in the enantioselective crystallization of racemic compounds.The enantiomeric excess（ee）of the induced crystal of threonine could be up to 95%.