Effect of the molecular weight and architecture on the size and glass transition of arborescent polyisobutylenes

This article discusses the characterization of arborescent (hyperbranched) polyisobutylenes (arb‐PIBs) by size exclusion chromatography and differential scanning calorimetry, in comparison with linear PIB standards. The radius of gyration (〈r g2〉1/2 = Rz), measured from the angle dependence of light scattering of high‐molecular‐weight arb‐PIBs, was significantly larger than the hydrodynamic radius (Rh) from size exclusion chromatography/viscometry, and the Rh values were significantly smaller than Rh of linear PIBs. The glass‐transition temperature of arb‐PIBs having a branch molecular weight higher than the critical entanglement molecular weight was dependent on both the total number‐average molecular weight and BR up to BR ∼ 15. A modified Fox–Flory equation is proposed to describe the effect of architecture on the thermal transition. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1770–1776, 2006 This article discusses the effect of architecture on the size and thermal transition of branched (arborescent of tree‐like) polyisobutylenes arb‐PIBs. The radius of gyration measured from the angle dependence of light scattering of high molecular weight arb‐PIBs was larger than the hydrodynamic radius (Rh) from SEC/viscometry, and Rh values were smaller than Rh of linear PIBs. The Tg of arb‐PIBs having branch molecular weight higher than the critical entanglement molecular weight was dependent on both the total Mn and BR up to BR ∼ 15. A modified Fox–Flory equation is proposed to describe the effect of architecture on thermal transition.