The compatibility of d8-poly(methyl methacrylate) (d8-PMMA) and a series of poly(n-alkyl methacrylate)s (PnAlkMA) is studied by systematic variation of the length of the n-alkyl group from ethyl (EMA) to n-pentyl (nPenMA). Simultaneously, a series of symmetric diblock copolymers comprised of d8-PMMA and of PnAlkMA ranging from ethyl to n-hexyl (nHMA) is synthesized. Small-angle X-ray data of bulk samples of d8-PMMA-b-PEMA show that this block copolymer is in the disordered state. A change in the χ over 1/T plot occurs between 120 and 130 °C owing to fluctuations. All other block copolymers are in the ordered state at any temperature. The neutron reflection data of d8-PMMA-b-PEMA show a damped cosine concentration depth profile characteristic for thin films of block copolymers in the disordered state. In contrast, the bilayer film of the respective homopolymer pair indicates immiscibility. Neutron reflection measurements on thin films of diblock copolymers ranging from d8-PMMA-b-PnPrMA to d8-PMMA-b-PnHMA and of bilayer films of d8-PMMA and the respective PnAlkMAs show a decreasing apparent interfacial width with increasing length of the n-alkyl group. Taking into account the contributions of capillary waves leads to the inherent interfacial width. By use of the theoretical approach of Matsen and Bates, it is possible to extract the Flory-Huggins χ-parameter between the blocks and the average segment length.
The behavior of block copolymers at various interfaces is studied by transmission electron microscopy and neutron reflection. A thin film of a symmetric diblock copolymer of styrene and methyl methacrylate forms layer structures when in contact with air and a random copolymer of styrene and acrylonitrile containing 35 wt% acrylonitrile. When the random copolymer has an acrylonitrile content of 25 wt%, a competition between layer formation and diffusion of disordered micelles takes place. Driving force for these processes are different interfacial tensions and a changing miscibility behavior as a function of acrylonitrile contents of the random copolymers. The ordering behavior of a symmetric diblock copolymer of deuterated styrene and isoprene in contact with poly(3,5‐dimethyl phenylene ether) is studied by neutron reflection. Polystyrene‐block‐poly(ethene‐co‐but‐1‐ene)‐block‐polystyrene with cylindrical PS microdomains shows an interfacial phase transition to lamellae near to the interface with different polymers. The morphological studies are in agreement with adhesion data obtained by peel tests on different bilayer specimens.
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