Synthesis of hyperbranched aromatic homo- and copolyesters via the slow monomer addition method

Citation
A. Mock et al., Synthesis of hyperbranched aromatic homo- and copolyesters via the slow monomer addition method, MACROMOLEC, 34(22), 2001, pp. 7692-7698
Citations number
32
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Organic Chemistry/Polymer Science
Journal title
MACROMOLECULES
ISSN journal
0024-9297 → ACNP
Volume
34
Issue
22
Year of publication
2001
Pages
7692 - 7698
Database
ISI
SICI code
0024-9297(20011023)34:22<7692:SOHAHA>2.0.ZU;2-V
Abstract
Random bulk polycondensation and the slow monomer addition (SMA) strategy h ave been employed for the preparation of hyperbranched aromatic homo- and c opolyesters, based on 3,5-bis(trimethylsiloxy)benzoyl chloride (AB(2) monom er) and 3-(trimethylsiloxy)benzoyl chloride (AB comonomer). Whereas random copolycondensation in bulk yielded limited molecular weights (M-n = 2900-84 00; SEC-LALLS in DMF/GHC), considerably higher molecular weights and low po lydispersities were obtained under slow monomer addition conditions (M-n = 83 000-278 000; PD = 1.09-1.49). Copolymerization of the AB(2) and AB monom ers resulted in polymers with controlled degrees of branching (DB) in the r ange 0-0.5. In the random copolycondensation the theoretical DB values coul d be confirmed by detailed analysis of the C-13 NMR data, demonstrating equ al reactivity of the comonomers. Using the slow monomer addition strategy ( SMA), the DB was significantly enhanced above the value of 0.5 for bulk AB( 2) polycondensation to 0.61-0.66, in agreement with theoretical predictions (DB = 0.66), and also high molecular weight polymers were obtained. Also, for all copolymerizations enhanced DBs were obtained. A strictly linear dep endence of the intrinsic viscosity [eta] on molecular weight was observed f or all copolymers, measured by online SEC viscosimetry. The Mark-Houwink ex ponents alpha (MH) clearly decreased with the DB and were in the range 0.18 -0.55.