Synthesis and Characterization of Brush-Shaped Hybrid Inorganic/Organic Polymers Based on Polyphosphazenes

Abstract

A series of densely grafted star-and combshaped molecular brushes composed of polystyrene, poly(tertbutyl acrylate), and poly(N-isopropylacrylamide) were prepared by atom transfer radical polymerization (ATRP) using either cyclotriphosphazenes or polyphosphazenes as initiators. The initiators were prepared by the introduction of a free hydroxyl group into the side chains of a phosphazene cyclic trimer and polymer, followed by esterification with 2-bromopropionyl bromide. The grafting conditions were optimized for various monomers. The kinetics of the reaction were firstorder with respect to the monomer concentration in both cyclotriphosphazene and polyphosphazene systems. The molecular weights of the resulting polymers were estimated by gel permeation chromatography (GPC). The side chains of the brush polymers were cleaved from the backbone and analyzed by GPC to confirm the synthesis of well-defined polymer brushes. Brushes based on poly(tert-butyl acrylate) were subjected to hydrolysis to yield negatively charged brushes. In addition, the lower critical solution temperature (LCST) of poly(N-isopropylacrylamide) brush polymers was measured by both dynamic light scattering (DLS) and differential scanning calorimetry (DSC), exhibiting a sharp phase transition at 33°C. Furthermore, starand comb-block copolymers with a hard polystyrene core and a soft poly(tert-butyl acrylate) shell were also synthesized.

Synthesis and self-assembly of thermosensitive double-hydrophilic poly(N-vinylcaprolactam)-b-poly(N-vinyl-2-pyrrolidone) diblock copolymers

“…When a PNIPAM segment is attached to another hydrophilic block, for example, poly(ethylene glycol) (PEG), these block copolymers can dissolve in water under the LCST and self‐associate to stable morphologies such as micelles and vesicles upon heating . On the other hand, if the PNIPAM block is conjugated to hydrophobic polymer blocks, the resultant copolymers can form assemblies at room temperature which can further aggregate into complex morphologies at high temperatures . Several studies reported on synthesis and assembly of triblock copolymers containing temperature‐responsive polymer segments .…”

Branched Macromolecular Architectures for Degradable, Multifunctional Phosphorus‐Based Polymers

“…[32] Such bottle-brush type organic-inorganic hybrid polymers can also be prepared via a "grafting-from" approach, polymerizing away from the functionalized polyphosphazene backbone, for example via atom transfer radical polymerization (ATRP) from alkyl bromide group functionalized polyphosphazenes. [58] Such high density bottle brush polymers could have wide reaching applications, one example of which includes quaternized organicinorganic hybrid brush polyphosphazenes being investigated for their antibacterial properties. [59] A "grafting-to" approach has also been achieved, via polyphosphazenes coupled onto branched organic polymers such as phosphoranimine-terminated poly(amidoamine) (PAMAM) dendrimers via cationic polymerization.…”

Preparation of UV-curable functionalized phosphazene-containing nanotube/polyurethane acrylate nanocomposite coatings with enhanced thermal and mechanical properties

“…[15][16][17][18][19][20] It is well known that phosphazene-containing polymers have been widely used as the optical materials, biomaterials, membrane materials, electrical and electrochromic materials, hybrid materials, etc., because of their superior high thermal stability and biocompatibility of the inorganic unit and inconceivable structural diversity. Presence of the inorganic phosphazene (-P=N-) unit in macromolecular backbones and the structural multiplicity of side groups, such as organic, organometallic or inorganic units, provides tremendous flexibility to functionalize the materials through physical or chemical modifications for numerous applications.…”