Thin homopolymer

The higher transparency coupled with the rigidity expected of a conventional polypropylene homopolymer is of particular interest in thin-wall moulding applications. 

The combined effects of a divalent Ca counterion and thermal treatment can be seen from studies of PMMA-based ionomers [16]. In thin films of Ca-salts of this ionomer cast from methylene chloride, and having an ion content of only 0.8 mol%, the only observed deformation was a series of long, localized crazes, similar to those seen in the PMMA homopolymer. When the ionomer samples were subject to an additional heat treatment (8 h at 100°C), the induced crazes were shorter in length and shear deformation zones were present. This behavior implies that the heat treatment enhanced the formation of ionic aggregates and increased the entanglement strand density. The deformation pattern attained is rather similar to that of Na salts having an ion content of about 6 mol% hence, substitution of divalent Ca for monovalent Na permits comparable deformation modes, including some shear, to be obtained at much lower ion contents. 

Another example of favorable synergistic effects in ionomer/homopolymer blends is evident from a study of the tensile properties of blends of an SPS ionomer with PS. Over most of the composition range these two polymers are incompatible. For small additions of the SPS ionomer to PS, TEM studies of cast thin films show that... 

UV light in a second step. In later work reported by Tazuke, Kimura et al. (6-8) successful photograftings on the polymer surface of thin films (polyethylene, polypropylene and polystyrene) were achieved with various monomers. In this work, grafting was induced by UV irradiation through the film which was in contact with a solution containing initiator and monomer. The method is slow and - in addition to surface grafting - large amounts of homopolymer are formed. 

Solutions of the copolymers (2a-k) were cast into thin films and heated to 350 °C to imidize the copolymer (Schemes 6-8), yielding polymers 3a-k. In each case, clear tough films were obtained indicating minimal homopolymer contamination. The thermal analyses for the copolymers are shown in Table 3 together with that of a polyimide homopolymer for comparison. It is important to note that the aryl ether composition increased after imidization due to the loss of ethanol in the imidization process. No detectable T was observed for the polyimide... 

An alternative route to prepare well-defined block copolymers is first to prepare the homopolymers with functional groups and then to connect them by noncovalent interactions [92-99], A systematic 4x4 library of block copolymers based on PSt and PEG connected by an asymmetrical octahedral (itXterpyridine) ruthenium complex at the block junction was reported [78], Moreover, the thin film morphology of this library was investigated. 

Like the homopolymers, fairly thin polymer thicknesses were observed for the copolymers [72]. Again for these block copolymer brushes, the MW and PDI are unknown, much less the actual constitution and voliune of the blocks on the polymer brush. The presence of the blocks can be confirmed where the sequence of the polymerization procedure assures consumption... 

Microdomains of block copolymer/ homopolymer blends 25-A-diameter Pd clusters Metal-ion precursors, introduced into cast thin films of polymer microdomains, are reduced by high pressure hydrogen 60,61... 

This chapter is organized as follows. Section 6.2 is concerned with experiments on binary block copolymer/homopolymer blends, Section 6.3 deals with experiments on ternary blends containing a block copolymer and in Section 6.4 experiments on binary blends of block copolymers are reviewed. Theory for the corresponding type of blend is discussed successively in Sections 6.5 to 6.7. Finally, experiments on thin films are discussed in Section 6.8, separately from the work on bulk blends, in keeping with earlier chapters. 

Thin films of block copolymer/homopolymer blends... 

Thin films of blends of block copolymer with two homopolymers... 

Density distributions at the interface of nearly symmetric PS-PMMA diblocks between high-molecular-weight PS and PMMA homopolymers were investigated using neutron reflectivity by Russell et al. (1991). Thin films were... 

---