CONFINEMENT-INDUCED DIFFERENCES BETWEEN DIELECTRIC NORMAL MODES AND SEGMENTAL MODES OF AN ION-CONDUCTING POLYMER

Dielectric measurement in the range 0.1 Hz to 1 MHz were used to study the motions of polymers and ions in an ion-conducting polymer, polypropylene oxide containing small quantities (on the order of 1%) of lithium ions (LiClO4), confined as a sandwich of uniform thickness between parallel insulating mica surfaces. In the dielectric loss spectrum, we observed three peaks; they originated from the normal mode of the polymer, segmental mode of the polymer, and ion motions. With decreasing film thickness, the peak frequencies corresponding to the normal mode and ion motion shifted to lower frequencies, indicating retardation due to confinement above 30 nm. This was accompanied by diminished intensity of the dielectric normal-mode relaxation, suggesting that confinement diminished the fluctuations of the end-to-end vector of the chain dipole in the direction between the confining surfaces. On the contrary, the segmental mode was not affected at that thickness. Finally, significant retardation of the segmental mode was observed only for the thinnest film (14 nm). The different dynamical modes of the polymer (segmental and slowest normal modes) respond with different thickness and temperature dependence to confinement.X1113sciescopu

Confinement-induced differences between dielectric normal modes and segmental modes of an ion-conducting polymer

Dielectric measurement in the range 0.1 Hz to 1 MHz were used to study the motions of polymers and ions in an ion-conducting polymer, polypropylene oxide containing small quantities (on the order of 1%) of lithium ions (LiClO4), confined as a sandwich of uniform thickness between parallel insulating mica surfaces. In the dielectric loss spectrum, we observed three peaks; they originated from the normal mode of the polymer, segmental mode of the polymer, and ion motions. With decreasing film thickness, the peak frequencies corresponding to the normal mode and ion motion shifted to lower frequencies, indicating retardation due to confinement above 30 nm. This was accompanied by diminished intensity of the dielectric normal-mode relaxation, suggesting that confinement diminished the fluctuations of the end-to-end vector of the chain dipole in the direction between the confining surfaces. On the contrary, the segmental mode was not affected at that thickness. Finally, significant retardation of the segmental mode was observed only for the thinnest film (14 nm). The different dynamical modes of the polymer (segmental and slowest normal modes) respond with different thickness and temperature dependence to confinement

Effective dispersion of fullerene with methacrylate copolymer in organic solvent and poly(methyl methacrylate)

Dispersion of fullerene, C 60, by addition of polymethacrylate dispersant in methyl methacrylate (MMA) and incorporation of C 60 into poly(methyl methacrylate) (PMMA) were investigated. Copolymers synthesized by radical copolymerization of MMA and 2-naphthyl methacrylate (NMA), poly(MMA-co-NMA), effectively dispersed C 60 in MMA to form clusters of 20 nm. In these cases, addition of minimal 110 naphthyl groups per unit C 60 molecule afforded to give clusters with minimum of 20 nm sizes. Furthermore, block copolymers, poly(MMA-b-NMA) with MMA/NMA mole ratio from 12:1 to 20:1, also efficiently dispersed C 60 to give formation of clusters of 20 nm size by addition of minimal 40 naphthyl groups per unit C 60 molecule, which was corresponding to approximate nine layers of naphthyl group in block copolymer adsorbed on the surface of the cluster. Hybrid films of C 60/PMMA, prepared by casting of C 60-dispersed solution containing PMMA, exhibited absorbance at 400 nm linearly increased with C 60 content