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Aliphatic Hyperbranched Copolyesters by Combination of ROP and AB 2 ‐Polycondensation
Author(s) -
Smet Mario,
Gottschalk Carsten,
Skaria Sunny,
Frey Holger
Publication year - 2005
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.200500397
Subject(s) - condensation polymer , polymer chemistry , copolymer , comonomer , trifluoromethanesulfonate , monomer , transesterification , hydroxymethyl , ring opening polymerization , branching (polymer chemistry) , polymerization , dispersity , polymer , chemistry , materials science , catalysis , organic chemistry
Abstract Summary: Hyperbranched aliphatic copolyesters have been prepared by the copolymerization of ε ‐caprolactone and 2,2‐bis(hydroxymethyl)butyric acid (AB 2 ‐monomer), catalyzed by (i) HfCl 4 (THF) 2 and (ii) diphenylammonium trifluoromethanesulfonate (DPAT), respectively. In both cases, copolymerization by combined ROP/AB 2 ‐polycondensation was achieved. The degree of branching ( DB ) and consequently the density of functional groups of the resulting copolyesters were controlled by the comonomer ratio in the feed. Molecular weights in the range $\overline M _{\rm n}$ = 22 000–166 000 g · mol −1 (GPC, PS standards) were obtained, with apparent polydispersity indices of 1.20 to 1.95. The DB was in the range 0.03–0.35. Remarkably, HfCl 4 (THF) 2 appeared to cause no transesterification of the ester bonds in the hyperbranched polymer formed. Further esterification or functionalization of the hydroxyl end groups of the hyperbranched polymers is therefore possible in a convenient two step/one pot process. The prepared hyperbranched polycaprolactones can be used as multifunctional initiators for the ROP of ε ‐caprolactone, which is also catalyzed by HfCl 4 (THF) 2 , resulting in multi‐arm star polymers. Diphenylammonium trifluoromethanesulfonate (DPAT) was also found to catalyze the combination of ROP and AB 2 polycondensation. However, the applicability of this system is restricted due to side reactions that can lead to crosslinking.Synthesis of hyperbranched copolyesters by combined ROP/polycondensation.