Cellulosic Polymer Blends 1: With Vinyl Polymers

This chapter reviews recent studies on blends of conventional cellulose esters (CEs), such as cellulose acetate (CA), cellulose propionate (CP), and cellulose butyrate (CB), with non-crystalline vinyl (co)polymers mainly comprising the N-vinyl pyrrolidone (VP) unit. The mixing behavior of the CE/VP-containing copolymer blends is seriously affected by the chain length (i.e., carbon number) and degree of substitution (DS) as to the acyl substituent of the CE component, and by the VP fraction in the copolymer component. Relatively low-substituted CEs are commonly miscible with VP-containing copolymers by virtue of hydrogen bond formation between the CE-hydroxyls and VP-carbonyls. The blend systems using CP and CB with higher DSs impart a “miscibility window” involved in the monomer composition that constitutes the copolymer component. This observation is interpretable as a result of the indirect CE–copolymer attraction driven by intra-copolymer repulsion. A convincing argument for the miscibility behavior is provided by assessing the attractive or repulsive interactions between the blend constituents in terms of the viscometric interaction parameter. In addition to the basic characterization of the blend miscibility and intermolecular interaction, we also survey some useful applications of miscible CE blends to functional films exhibiting improved adsorption, optical, or thermomechanical properties. Particular attention is paid to the molecular orientation and optical anisotropy induced in deformed films of CA/VP-methyl methacrylate polymer blends.