Synthesis of Organic/Inorganic Hybrid Quatrefoil-Shaped Star-Cyclic Polymer Containing a Polyhedral Oligomeric Silsesquioxane Core

• Published in: Macromolecules Vol. 42; no. 8; pp. 2903 - 2910
• Main Authors: Ge, Zhishen, Wang, Di, Zhou, Yueming, Liu, Hewen, Liu, Shiyong
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 28.04.2009
• Subjects: Applied sciences; Exact sciences and technology; Inorganic and organomineral polymers; Physicochemistry of polymers; Preparation; 1,3-Dipolar cycloaddition; Triazole derivative copolymer; End group; Molecular structure; Atom transfer polymerization; Propargylic compound; Polycyclic compound; Cyclic copolymer; Silsesquioxane copolymer; Experimental study; Azides; Chemical modification; Cyclization; Preparation; Nucleophilic substitution; Styrene copolymer
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma802585k

We report the synthesis of quatrefoil-shaped star-cyclic polystyrene, star-cyclic PS, containing a polyhedral oligomeric silsesquioxane (POSS) core via the combination of atom transfer radical polymerization (ATRP) and click chemistry techniques. The obtained star-cyclic PS represents a new chain topology in the category of nonlinear-shaped polymers. Using octa(3-chloropropyl) polyhedral oligomeric silsesquioxane, POSS-(Cl)8, as the starting material, its azidation and subsequent click reaction with a slight excess of propargyl 2-bromobutyrate afforded octafunctional initiator, POSS-(Br)8. 8-arm star-linear PS-N 3 was obtained by the azidation of star-linear PS-Br, which was synthesized by the ATRP of styrene using POSS-(Br)8 as the initiator. Model reaction between α,ω-diazido-terminated PS (N 3-PS-N 3) and difunctional propargyl ether confirmed that bimolecular click cyclization reaction can effectively occur under highly dilute conditions. Next, intramolecular click ring closure of star-linear PS-N 3 was conducted under highly dilute conditions, using propargyl ether as the difunctional linker and CuBr/PMDETA as the catalyst, affording quatrefoil-shaped star-cyclic PS. Gel permeation chromatography (GPC), 1H NMR, and FT-IR analysis confirmed the complete consumption of azide moieties in star-linear PS-N 3 and that the coupling reaction proceeded via the intramolecular manner. Differential scanning calorimetry (DSC) results revealed that star-cyclic PS possesses higher glass transition temperature (T g) than that of star-linear PS, possibly due to the ring topology of PS arms in the former.