A new chemical modification of liquid polybutadienes: Radical addition of aliphatic aldehydes onto pending vinyl groups

The Power of RAFT for Creating Polymers Having Imbedded Side-Chain Functionalities: Norbornenyl-Functionalized Polymers and their Transformations via ROMP and Thiol-ene Reactions

Robust, efficient and orthogonal chemistries are becoming increasingly important tools for the construction of increasingly sophisticated materials. In this article, the selectivity of reversible addition–fragmentation chain transfer (RAFT)-based radical polymerization of bifunctional monomers is exploited for the preparation of statistical and block copolymers that contain imbedded side-chain functionalities, which are then shown to exhibit two different orthogonal types of chemical reactivity to afford discrete nanoscale objects and functional derivative structures. Based on the radical reactivity ratios calculated from Alfrey–Price theory, a bifunctional monomer 4-(5′-norbornene-2′-methoxy)-2,3,5,6-tetrafluorostyrene (1) was designed and synthesized, for its highly reactive tetrafluorostyrenyl group relative to its norbornene (Nb) group. Selective RAFT copolymerization of 1 with styrene (St) afforded copolymers with over 50 mol-% structural units having a pendent norbornenyl functionality while maintaining narrow molecular weight distribution (polydispersity index (PDI) = 1.23). Diblock copolymers (PDI = 1.09–1.23) with Nb side-chain substituents regioselectively placed along one segment of the block copolymer structure were also prepared by RAFT copolymerizations of 1 with St or 2,3,4,5,6-pentafluorostyrene, using either polystyrene or poly(styrene-alt-maleic anhydride)-based macro chain-transfer agents. A well-defined star block copolymer (PDI = 1.23) having a poly(norbornene)-based core and polystyrene arms was obtained by ring-opening metathesis polymerization using the regioselective diblock copolymer PSt-b-P(1-co-St) as the multifunctional macromonomer and Grubbs’ catalyst (first generation) as the initiator. Photo-induced thiol-ene reactions of Nb-functionalized polymers with thiols were fast and efficient, yielding polymers with new side-chain structures.

Well-Defined Polymers Bearing Pendent Alkene Functionalities via Selective RAFT Polymerization

A facile synthetic approach for the preparation of well-defined (co)polymers bearing pendent alkene functionalities was established by selective reversible addition-fragmentation chain transfer (RAFT) (co)polymerization. A divinyl monomer 4-(3'-buten-1'-oxy)-2,3,5,6-tetrafluorostyrene (1) with a styrenyl group and a pendent alkene group was synthesized. Due to a very high reactivity of the styrenyl group relative to the alkene group in 1, functional fluoro(co)polymers with both well-defined structures and pendent alkene groups were prepared by RAFT polymerizations of 1 and copolymerization of 1 with pentafluorostyrene (PFS). Alkene-functionalized diblock copolymers were also prepared by RAFT copolymerization of 1 with PFS or styrene, extending from a poly(styrene-alt-maleic anhydride) macro-chain transfer agent. Hydrolysis and ammonolysis of these copolymers resulted in amphiphilic diblock fluorocopolymers with alkene-functionalized hydrophobic segments, which were shown to form internally-functionalized micelles in THF-water.