Synthesis Characterization and Morphology of a Cis 1,4 Polyisoprene/Poly n-Butylmethacrylate Diblock Copolymer.
Abstract
Homogeneous anionic polymerization methods were employed to synthesize a diblock copolymer of the form (A)(n)-b-(B)(m) in which repeat unit A is isoprene, B is n-butylmethacrylate and b is a single unit of 1,1 diphenylethylene. Various physical-chemical characterization methods were employed to determine that the molecular weights of the A and B blocks are 80,000 and 160,000 g/mole respectively. NMR spectra indicated that the poly n-butylmethacrylate moiety is composed predominantly of syndiotactic triads. Thermal analysis and dynamic mechanical testing were used to determine the polyisoprene and poly n-butylmethacrylate glass transition temperatures, which were around -70 and 20 C respectively; the poly n-butylmethacrylate transition observed in the viscoelastic experiments was unusually broad, covering more than 75 C from onset to completion. Thin films of the diblock copolymer prepared by solvent evaporation casting methods, using a variety of solvents and a wide range of solvent evaporation rates, showed a variety of morphologies in transmission electron micrographs. Most notable among these was a structure obtained in rapid-evaporation castings which contained relatively large regions of homogeneous diblock copolymer embedded in the microphase-separated material. While these homogenized regions remain unchanged indefinitely in the bulk material at room temperature, they tend to decompose to the stable microphase-separated material upon heating or upon addition of solvent. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 14, 1979
- Accession Number
- ADA078731
Entities
People
- Frank S. Bates
- Robert E. Cohen
Organizations
- Massachusetts Institute of Technology