Cyclizations in hyperbranched aliphatic polyesters and polyamides

Abstract

Hyperbranched aliphatic polyesters of 2,2′‐bis‐(hydroxymethyl) propanoic acid and hyperbranched aliphatic polyamides obtained from new carboxy‐ and amino‐functionalized caprolactams were studied by NMR spectroscopy and MALDI‐TOF mass spectrometry. Ring‐chain equilibria taking place through intramolecular hydroxy‐ester, carboxy‐amide or amine‐amide interchanges and leading to the formation of cyclic branches or end‐groups were found to exert a predominant influence on the molar mass of these hyperbranched polymers. A number of intra‐ or intermolecular side reactions, such as the formation of ethers in polyesters and the formation of anhydrides, imides, amidines and secondary amines in polyamides were also detected and resulted in polymer crosslinking on prolonged heating. The existence of such ring‐chain equilibria and side‐reactions make the control of hyperbranched polymer structure much more difficult than generally accepted.

Controlled synthesis of crosslinked polyamide 6 using a bis-monomer derived from cyclized lysine

“…Here the crosslinking was demonstrated by the insolubility of the resulting materials, usually solubilized in trifluoroethanol, and the higher glass transition temperatures of the materials with the increasing monomer feed ratio g-ethylene ketal-ε-caprolactam/ε-caprolactam. Hyperbranched poly(ε-caprolactam), which can contain fractions of crosslinked PA6, were prepared by acidolytic ring-opening polymerization of g-aminoethyl-ε-caprolactam or g-carboxyethyl-ε-caprolactam [22]. A melt shear viscosity polyamide (i.e.…”

Reversible Cross-Linking of Aliphatic Polyamides Bearing Thermo- and Photoresponsive Cinnamoyl Moieties

“…Overberger et al studied the ring-opening polymerization of γ- tert -butoxymethylcaprolactam by obtaining soluble copolyamide owing to hydroxymethyl pendant groups. The hydrolytic ring-opening polymerization γ-phenylsulfonatecaprolactam was successfully reported by Nijenhuis et al γ-Carboxyethylcaprolactam and γ-aminoethylcaprolactam were used for the synthesis of hyperbranched aliphatic polyamides . It is worth noting that the synthesis of these monomers requires several or complex reaction steps with moderate yields.…”

“…The hydrolytic ring-opening polymerization γ-phenylsulfonatecaprolactam was successfully reported by Nijenhuis et al 35 γ-Carboxyethylcaprolactam and γ-aminoethylcaprolactam were used for the synthesis of hyperbranched aliphatic polyamides. 36 It is worth noting that the synthesis of these monomers requires several or complex reaction steps with moderate yields. Recently, Mathias et al reported the AROP of γ-ethylene ketal-ε-caprolactam.…”

New aliphatic hyperbranched polyester polyols based on 1,3,5‐tris(2‐hydroxyethyl) cyanuric acid as a core

“…The deviation of the calculated M n values from the theoretical ones is more pronounced at higher monomer/core ratio, i.e., higher generations. Cyclization36, 37 and/or self‐condensation33 of bisMPA, as side reactions during the synthesis process, are probably the main reasons for this deviation. Such side reactions may be enhanced at higher conversion and higher generation resulting in branches of lower molar masses, which particularly reduce the number average molecular weight.…”