Synthesis and characterization of novel dendritic (arborescent, hyperbranched) polyisobutylene-polystyrene block copolymers

• Published in: Journal of polymer science. Part A, Polymer chemistry Vol. 43; no. 9; pp. 1811 - 1826
• Main Authors: Puskas, Judit E., Kwon, Yongmoon, Antony, Prince, Bhowmick, Anil K.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01-05-2005; Wiley
• Subjects: Applied sciences; arborescent; block copolymers; characterization; Exact sciences and technology; hyperbranched; living carbocationic polymerization; Organic polymers; Physicochemistry of polymers; polyisobutylene; Polymerization; polystyrene; Preparation, kinetics, thermodynamics, mechanism and catalysts; synthesis; synthesis; block copolymers; living carbocationic polymerization; hyperbranched; polystyrene; Mechanical properties; Thermoplastic rubber; Cationic polymerization; Surface topography; Branched copolymer; Experimental study; Dynamic mechanical properties; Preparation; Styrene; Isobutene copolymer; polyisobutylene; Lattice structure; characterization; Block copolymer; Dendritic structure; arborescent; Styrene copolymer
• ISSN: 0887-624X; 1099-0518
• DOI: 10.1002/pola.20638

The synthesis of novel arborescent (arb; randomly branched, “tree‐like,” and often called “hyperbranched”) block copolymers comprised of rubbery polyisobutylene (PIB) and glassy polystyrene (PSt) blocks (arb‐PIB‐b‐PSt) is described. The syntheses were accomplished by the use of arb‐PIB macroinitiators (prepared by the use of 4‐(2‐methoxyisopropyl) styrene inimer) in conjunction with titanium tetrachloride (TiCl4). The effect of reaction conditions on blocking of St from arb‐PIB was investigated. Purified block copolymers were characterized by 1H NMR spectroscopy and Size Exclusion Chromatography (SEC). arb‐PIB‐b‐PSt with 11.7–33.8 wt % PSt and Mn = 468,800–652,900 g/mol displayed thermoplastic elastomeric properties with 3.6–8.7 MPa tensile strength and 950–1830% elongation. Samples with 26.8–33.8 wt % PSt were further characterized by Atomic Force Microscopy (AFM), which showed phase‐separated mixed spherical/cylindrical/lamellar PSt phases irregularly distributed within the continuous PIB phase. Dynamic Mechanical Thermal Analysis (DMTA) and solvent swelling of arb‐PIB‐b‐PSt revealed unique characteristics, in comparison with a semicommercial PSt‐b‐PIB‐b‐PSt block copolymer. The number of aromatic branching points of the arb‐PIB macroinitiator, determined by selective destruction of the linking sites, agreed well with that calculated from equilibrium swelling data of arb‐PIB‐b‐PSt. This method for the quantitative determination of branching sites might be generally applicable for arborescent polymers. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1811–1826, 2005
The synthesis of novel arborescent (arb; randomly branched, “tree‐like,” and often called “hyperbranched”) block copolymers comprised of rubbery polyisobutylene (PIB) and glassy polystyrene (PSt) blocks (arb‐PIB‐b‐PSt) is described. arb‐PIB‐b‐PSt with 11.7–33.8 wt % PSt and Mn = 468,800–652,900 g/mol displayed thermoplastic elastomeric properties with 3.6–8.7 MPa tensile strength and 950–1830% elongation. arb‐PIB‐b‐PSt swelled five times as much as a linear block copolymer, and XPS showed that the surface of the blocks is covered with a 10 nm thin PIB layer.