Molecular weights homopolymer-blend thin films

For instance, order-disorder transitions of BCP blends (typically related to macrophase separation processes) in thin films have been studied by Jeong et al. [48]. They used mixtures of PS-b-PMMA having PMMA cylindrical microdomains with homopolymers of either PMMA or poly(ethylene oxide) (PEO) and studied the morphological transitions and the formation of macrophase-separated domains in thin films (Fig. 6.7). Whereas the microdomains in all thin films are oriented perpendicular to the film surface, they found that the miscibility between PMMA homopolymer and PMMA block in thin film was enhanced compared with that in bulk at a given molecular weight of PMMA homopolymer. Equally, the PMMA homopolymer chains in thin films were more localized to the center of PMMA microdomains than in the bulk, which results in a larger increase of the lattice spacing (D) in the former. 

Polyolefin materials used for the battery separator are based on a homopolymer or a blend of polyethylene (PE) and polypropylene (PP) in a number of combinations between high density polyethylene (HOPE) and ultrahigh molecular weight polyethylene (UHMWPE). The methods for manufacturing the microporous polyolefin membranes can be divided into the dry process and wet process. Both processes contain an extmsion step to produce a thin film, and employ one or more orientation steps to impart porosity and increase tensile strength. The membranes made by diy process show a distinct slit-pore microstmcmre, while those by wet process feamre interconnected spherical or elliptical pores. 

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