Molecular Mobility of Molecular Brushes With a Polyimide Backbone and Polymethylmethacrylate Side Chains of Different Lengths

Abstract

The molecular mobility of polyimide (PI) brushes, i.e., graft-copolymers with a polyimide backbone and PMMA side chains of different lengths, is studied by the dielectric spectroscopy method. Three dipolar polarization regions are found in the temperature range from -150 to 200 • C: β-, β 1 , and α-processes. The β-process is due to a local mobility of polar groups of the PI backbone in the glassy state. Ester groups of polymethylmethacrylate (PMMA) side chains are responsible for two forms of the molecular mobility: a local mobility in the glassy state (β 1 -process) and a cooperative segmental motion of the skeletons of the PMMA side chains (α-process). The parameters of the β-and β 1 -processes are weakly dependent on the side chain's length. For the α-process, the molecular mobility of the PMMA side chains decreases with increasing their length.

Dielectric spectroscopy and molecular modeling of branched methacrylic (co)polymers containing nonlinear optical chromophores

“…5) for PI, FI, FIII almost coincide with those for conventional PMMA [18]. Thus one may suggest that in the oligomers under study this process is also determined by the mobility of pendant ester groups.…”

“…[18,20] that in PMMA the polarization of ester groups being the only polar ones, contributes to two processes: local displacements in the glassy state and reorientation in the rubbery state occurring at the segmental motions, resulting in b 1 and a processes, respectively (see curves 2 0 and 3 0 in Fig. 5а).…”

“…That is why to identify molecular mechanisms of b, b 1 , and a process in PI, FI, and FIII one may use the data on dielectric relaxation for PMMA [18,23] and comb-like methacrylic copolymers with chromophores in side-chains [18e21]. Polymer architectures of comb-like polymethacrylates and studied here branched methacrylic copolymers are different.…”

Study of Dynamic Rheological, Dynamic Mechanical and Creep Properties of Acrylonitrile Styrene Acrylate (ASA)/Zn+2poly(ethylene-co-methacrylic acid) Ionomer Blend

“…The brush polymers are formed by either physisorption (physically absorbed on polymer backbone surface) or covalent attachment process, which involves 'grafting-onto', 'grafting-from' or combination of grafting-onto and graftingfrom strategy (49). The versatile applications of polymer brush is due to its specific features like improved backbone rigidity, the partially or fully extended perpendicular side chains with minimum or no entanglements resulting into an ordered structure (50).…”