Click construction of spiro- and bridged-quatrefoil polymer topologies with kyklo-telechelics having an azide group.
Unprecedented tetracyclic polymer topologies with spiro- and a bridged-type quatrefoil forms are effectively constructed through an alkyne-azide, click-linking reaction by employing a kyklo-telechelic poly(tetrahydrofuran), poly(THF), precursor having an azide group, obtained through an electrostatic self-assembly and covalent fixation (ESA-CF) process, and complementary tetrafunctional alkyne reagents of either a pentaerythritol derivative or a four-armed star telechelic polymer precursor.
Sequential “Click” Synthesis of “Nano-Diamond-Ring-like” Giant Surfactants Based on Functionalized Hydrophilic POSS/C60 Tethered with Cyclic Polystyrenes
This paper reports the design and facile synthesis of a novel series of “nano-diamond-ring-like” giant surfactants composed of a functionalized hydrophilic polyhedral oligomeric silsesquioxane (such as dihydroxyl-functionalized DPOSS) or fullerene (such as carboxylic acid-functionalized AC60) head as the “diamond” and a hydrophobic, cyclic polystyrene (CPS) tail as the “ring”. The synthetic route combines several steps of “click-type” reactions, demonstrating highly efficient and modular features. Starting from a specifically designed initiator, trifunctional linear polystyrene (LPS) precursors bearing vinyl, bromo, and alkyne groups were prepared by atom transfer radical polymerization (ATRP). Upon the subsequent azidation of LPS, copper-catalyzed Huisgen [3 + 2] cycloaddition reaction was employed to afford vinyl-functionalized CPS ring in high yield and purity. The vinyl group was then subjected to the thiol–ene reaction to introduce an azide group onto the CPS, providing an azide-functionalized CPS (C...
Designing an “A‐Ring‐with‐Branches” Polymer Topology by Electrostatic Self‐Assembly and Covalent Fixation with Interiorly Functionalized Telechelics Having Cyclic Ammonium Groups
The increasing diversity in polymer architectures has offered better opportunities in the development of novel polymer materials of unprecedented properties and functions, eventually leading to future nanotechnology. 2] While a linear polymer architecture, possessing two chain ends, is a fundamental polymer topology, other polymer architectures possessing multiple chain ends and branch points, such as star polymers, 4] polymacromonomers, 6] hyperbranched polymers, and dendrimers, 9] have become increasingly common. Another unique class of basic polymer architecture is a cyclic topology without any chain ends. Single and double cyclic, i.e. eightshaped, polymer architectures have been realized so far. – 16] A wider variety of polymer topologies is envisaged by the combination of cyclic and linear polymer units. In this regard, a polymer of a-ring-with-a-branch structure, i.e. a tadpole polymer was also reported. 15, 17] Yet a practical and high yield synthesis of these class of polymers is an ongoing challenge. We recently developed an electrostatic self-assembly and covalent fixation process for the efficient construction of a variety of macromolecular architectures containing cyclic polymer units. 18] In this method, we have utilized telechelic poly(THF)s with cyclic ammonium groups carrying various multi-carboxylate counterions. Under appropriate dilution, the ionic polymer precursors completely disaggregates 19] into a smallest assembly, with balancing the charges between cations and anions. The subsequent covalent fixation through the ring-opening reaction of the cyclic ammonium groups by carboxylate counterions provides a variety of polymer architectures comprising a single or multiple cyclic polymer units. We also demonstrated the effective construction of a polymer with a-ring-with-a-branch structure by making use of a spontaneous three-component self-assembly of monoand bifunctional telechelics (Scheme 1) with a trifunctional counterion. As a further extension to the preceding studies, we report here on an efficient polymer cyclization of newly synthesized poly(THF) precursors having interiorly located pyrrolidinium groups, namely, eso-telechelics. Thus, an unusual polymer of a-ring-withtwo-branches structure 21] has been constructed effectively (Scheme 1). Communication: A novel and unusual polymer topology, i.e. a-ring-with-two-branches, has been constructed efficiently by making use of an interiorly functionalized poly(tetrahydrofuran) (poly(THF)) having two pyrrolidinium groups. The dicarboxylate counterion, i. e. terephthalate, was then introduced by an ion-exchange reaction of the interiorly located pyrrolidinium group. Subsequent heat treatment under appropriate dilution caused an efficient polymer cyclization to produce an a-ring-with-twobranches polymer topology in high yield through the selective and quantitative ring-opening of the pyrrolidinium groups by the dicarboxylate counterion.