Jayakannan, M and Ramakrishnan, S (2000) Effect of Branching on the Thermal Properties of Novel Branched Poly(4-ethyleneoxy benzoate). In: Journal of Polymer Science Part A: Polymer Chemistry, 38 (1). pp. 261-268.
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Poly(4-ethyleneoxy benzoate) (PEOB) was synthesized by the self-condensation of ethyl 4-(2-hydroxyethoxy) benzoate (E4HEB) under transesterification conditions. Branched PEOB was prepared by the condensation of E4HEB with an $AB_2$ monomer, ethyl 3,5-bis(2-hydroxyethoxy) benzoate (EBHEB), under similar conditions. Varying amounts of branching (0–50%) were introduced into the linear polymer by changes in the composition of the comonomers in the feed. The solution viscosity of the polymers indicated that they had reasonable molecular weights; the extent of branching in these copolymers was established from their $^1H$ NMR spectra. Differential scanning calorimetry studies indicated that, as expected, the introduction of branching drastically affected the percent crystallinity of the copolymers (as seen from their $\Delta H_m$, the enthalpy of melting), and when the extent of the incorporation of the $AB_2$ monomer exceeded 10 mol %, the copolymers were completely amorphous. The melting temperatures of the copolymers decreased with an increase in the branching content, whereas the peak crystallization temperature in quenched (amorphous) samples followed the exactly opposite trend. The glass-transition temperatures $(T_g)$ of the branched copolymers first decreased at low extents of branching, passed through a minimum, and then increased to attain the $T_g$ of the pure hyperbranched polymer of EBHEB.
|Item Type:||Journal Article|
|Additional Information:||Copyright of this article belongs to John Wiley & Sons, Inc.|
|Keywords:||AB2 monomer;branched polymer;glass transition.|
|Department/Centre:||Division of Chemical Sciences > Inorganic & Physical Chemistry|
|Date Deposited:||22 Oct 2008 07:11|
|Last Modified:||19 Sep 2010 04:51|
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