High-Strain-Induced Deformation Mechanisms in Block-Graft and Multigraft Copolymers
- Fraunhofer IWM, Freiburg, German
- Qingdao University of Science and Technology, Qingdao CHINA
- Polymer Research Institute, Dresden Germany
- ORNL
The molecular orientation behavior and structural changes of morphology at high strains for multigraft and block graft copolymers based on polystyrene (PS) and polyisoprene (PI) were investigated during uniaxial monotonic loading via FT-IR and synchrotron SAXS. Results from FT-IR revealed specific orientations of PS and PI segments depending on molecular architecture and on the morphology, while structural investigations revealed a typical decrease in long-range order with increasing strain. This decrease was interpreted as strain-induced dissolution of the glassy blocks in the soft matrix, which is assumed to affect an additional enthalpic contribution (strain-induced mixing of polymer chains) and stronger retracting forces of the network chains during elongation. Our interpretation is supported by FT-IR measurements showing similar orientation of rubbery and glassy segments up to high strains. It also points to highly deformable PS domains. By synchrotron SAXS, we observed in the neo-Hookean region an approach of glassy domains, while at higher elongations the intensity of the primary reflection peak was significantly decreasing. The latter clearly verifies the assumption that the glassy chains are pulled out from the domains and are partly mixed in the PI matrix. Results obtained by applying models of rubber elasticity to stressstrain and hysteresis data revealed similar correlations between the softening behavior and molecular and morphological parameters. Further, an influence of the network modality was observed (randomgrafted branches). For sphere formingmultigraft copolymers the domain functionality was found to be less important to achieve improved mechanical properties but rather size and distribution of the domains.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- DE-AC05-00OR22725
- OSTI ID:
- 1034706
- Journal Information:
- Macromolecules, Vol. 44, Issue 23; ISSN 0024-9297
- Country of Publication:
- United States
- Language:
- English
Similar Records
All-acrylic multigraft copolymer superelastomers
Synthesis and Structure - Property Relationships for Regular Multigraft Copolymers