Multiblock Copolymers of Norbornene and Cyclododecene: Chain Structure and Properties.

Yulia I Denisova,Ivan S Levin,Maria L Gringolts,Georgiy A Shandryuk,Eugene Sh Finkelshtein,Alexander Ya Malkin,Vsevolod A Zhigarev,Yaroslav V Kudryavtsev,Marianna P Arinina

doi:10.3390/polym13111756

Abstract

We investigate the structure–property relations of the multiblock copolymers of norbornene with cyclododecene synthesized via the macromolecular cross-metathesis reaction between amorphous polynorbornene and semicrystalline polydodecenamer in the presence of the first-generation Grubbs catalyst. By adjusting the reaction time, catalyst amount, and composition of the initial system, we obtain a set of statistical multiblock copolymers that differ in the composition and average length of norbornene and dodecenylene unit sequences. Structural, thermal, and mechanical characterization of the copolymers with NMR, XRD, DSC (including thermal fractionation by successive self-nucleation and annealing), and rotational rheology allows us to relate the reaction conditions to the average length of crystallizable unit sequences, thicknesses of corresponding lamellas, and temperatures of their melting. We demonstrate that isolated dodecenylene units can be incorporated into crystalline lamellas so that even nearly random copolymers should retain crystallinity. Weak high-temperature endotherms observed in the multiblock copolymers of norbornene with cyclododecene and other cycloolefins could indicate that the corresponding systems are microphase-separated in the melt state.

Highlights

Chain structure in copolymers is usually characterized by the average lengths of blocks consisting of chemically or structurally different monomer units
We investigated the thermal properties of novel multiblock copolymers of norbornene and cyclododecene and quantitatively related the structural parameters of polymer chains to the characteristics of crystallites formed by trans dodecenylene unit sequences
The copolymers with the number average length of such sequences exceeding 4.5 units crystallize similar to polydodecenamer and form crystalline lamellas up to 15 nm thick, whereas the copolymers with shorter trans dodecenylene blocks generate crystallites that are more uniform in size and not exceeding 8 nm

Summary

Introduction

Chain structure in copolymers is usually characterized by the average lengths of blocks consisting of chemically or structurally different monomer units. Even a moderate tendency toward blockiness in the monomer unit distribution can result in considerably different properties relative to completely random polymers of the same composition [1,2,3,4,5]. Depending on the synthetic conditions, the monomer unit order in copolymer chains varies from fully determined in the so-called sequence-defined polymers [11] to statistical in the products of macromolecular reactions, such as post-modification, end coupling, or interchain exchange [12]. All the rich variety of properties is based on the ability of block copolymers to self-assemble into different morphologies, in which monomer unit interactions are balanced by their connectivity in polymer chains [18,19]. Being inferior to diblock copolymers in the accuracy and alignment of domain boundaries, multiblocks demonstrate better mechanical properties, biocompatibility, biodegradability, compatibilizing ability, and tendency to form bicontinuous phases for effective ionic and molecular transport [20,21,22,23,24,25]

Methods

Results

Conclusion