Abstract

An approach to the synthesis of the novel molecular brushes with a polyimide (PI) backbone and poly(ε-caprolactone) (PCL) side chains was developed. To obtain such copolymers, a combination of various synthesis methods was used, including polycondensation, atom transfer radical polymerization (ATRP), ring opening polymerization (ROP), and Cu (I)-catalyzed azide-alkyne Huisgen cycloaddition (CuAAC). ATRP of 2-hydroxyethyl methacrylate (HEMA) on PI macroinitiator followed by ROP of ε-caprolactone (CL) provided a “brush on brush” structure PI-g-(PHEMA-g-PCL). For the synthesis of PI-g-PCL two synthetic routes combining ROP and CuAAC were compared: (1) polymer-analogous transformations of a multicenter PI macroinitiator with an initiating hydroxyl group separated from the main chain by a triazole ring followed by ROP of CL, or (2) a separate synthesis of macromonomers with the desirable functional groups (polyimide with azide groups and PCL with terminal alkyne groups), followed by a click reaction. Results showed that the first approach allows to obtain graft copolymers with a PI backbone and relatively short PCL side chains. While the implementation of the second approach leads to a more significant increase in the molecular weight, but unreacted linear PCL remains in the system. Obtained macroinitiators and copolymers were characterized using 1H NMR and IR spectroscopy, their molecular weight characteristics were determined by SEC with triple detection. TGA and DSC were used to determine their thermal properties. X-ray scattering data showed that the introduction of a polyimide block into the polycaprolactone matrix did not change the degree of crystallinity of PCL.

Highlights

  • Polyimides (PI) are an essential class of polymers with a set of valuable properties

  • Atom transfer radical polymerization (ATRP) has been successfully used to synthesize many types of copolymers, it remains a challenge to synthesize copolymers of different architectures using monomers that polymerize through fundamentally different mechanisms, such as atom transfer radical polymerization (ATRP) and ring opening polymerization (ROP)

  • A typical synthesis procedure is as follows: 0.05 g (0.23 mmol per initiating group) of PI-g-poly(2-hydroxyethyl methacrylate) (PHEMA) was added to a 25-mL Schlenk flask equipped with a magnetic stirrer, and three freeze−pump−thaw cycles were carried out, after which the flask was filled with argon

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Summary

Introduction

Polyimides (PI) are an essential class of polymers with a set of valuable properties. Copolymers of PCL with poly(octadecyl methacrylate) (POMA) and poly(N,N-dimethylamino-2-ethyl methacrylate) (PDMAEMA) PCL-b-PODMA-b-PDMAEMA or PCL-b-(PODMA-co-PDMAEMA) were obtained in [5], in which the PODMA block had a "pseudo-brush" structure due to long aliphatic tails Another example of a successful combination of the different methods of controlled polymerization is the synthesis of a three-armed star-shaped polymer with arms of different structures, for which different methods were used [4]. An efficient method for the synthesis of linear di- and triblock copolymers with PCL blocks with narrow molecular weight distribution is to carry out ROP on mono- or difunctional polymer initiators. This work is devoted to the development of methods for the synthesis of previously undescribed molecular brushes with a PI backbone and PCL side chains To obtain such copolymers, a combination of various synthesis methods was used, including polycondensation, ATRP, ROP, and Cu (I) catalyzed azidealkyne Huisgen cycloaddition (CuAAC) [27]

Materials
Introduction of Azide Groups into Polyimide
Introduction of Distant Hydroxyl Groups to Polyimide
Synthesis of Linear Homopolymer PCL with Terminal Alkyne Groups
Synthesis of Grafted Copolyimides PI-g-PCL
Results and Discussion
Synthesis of Multifunctional Polyimide Initiators
Synthesis of Molecular Brushes with a PI Backbone and PCL Side Chains by
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