An NMR study of mobility in a crystalline side‐chain comblike polymer

Abstract

Carbon-13 spin-lattice relaxation times are measured for poly(octadecyl acrylate) above and below the melting point of the crystalline side chains. The chain backbone has long spin-lattice relaxation times below the melting point that shorten by more than an order of magnitude as the melting point range is traversed. Below the melting point, the backbone is nearly immobilized with spin-lattice relaxation changing very slowly with temperature. Above the melting point, the shorter spin-lattice relaxation times are typical of a rubber above the glass transition and decrease with increasing temperature. The methylene groups in the side chain are quite mobile well below the melting point, indicating fairly rapid anisotropic motion within the crystal. The methyl group at the end of the chain and the adjacent methylene group have longer spin-lattice relaxation times, indicating the greatest side-chain mobility at the end, which is in the middle of the crystal structure. The side-chain carbon adjacent to the carbonyl group is as mobile as the majority of the side-chain carbon, indicating sidechain mobility extends to all of the side-chain CH 2 groups. The abrupt transition in the mobility of the backbone is not typical of the amorphous phase in a semicrystalline polymer where the backbone units can crystallize. The close proximity of every backbone segment to the crystalline domain locks backbone segmental motion below the melting point. Melting and crystallization of the side chains switch segmental motion of the backbone on and off.

Synthesis of poly(octadecyl acrylate‐b‐styrene‐b‐octadecyl acrylate) triblock copolymer by atom transfer radical polymerization

“…An outstanding feature is the liquid-crystal and thermochromic properties. [1][2][3][4][5][6] Moreover, the biphasic structure of comblike poly(octadecyl acrylate) gives rise to unique transport properties, [7][8][9] which make it attractive to mimic barrier synthetic composites and biological structures related to the permeation processes. In addition, copolymers containing ODA show shape memory behaviors attributed to a reversible order-disorder transition associated with the interaction between the alkyl side chains of ODA units.…”

Conformational Effect of Silica-supported Poly(octadecyl acrylate) on Molecular-Shape Selectivity of Polycyclic Aromatic Hydrocarbons in RP-HPLC

“…The peaks at 14 ppm and 29.7 ppm can be assigned to be C18 as terminal methyl groups and C4 -C14 as most of the methylene groups, respectively. Some peaks at 64.6 ppm (C1) and 41.3 ppm (C20), assigned by previous works, 28 were also used to determine the chemical shifts of C2, C3, and C15 -C19. Additional supporting data were obtained by the 2D-INADEQUATE test.…”

Structural analysis of polymer-brush-type cellulose β-ketoesters by molecular dynamics simulation

“…So far, various apparatuses have been used for structural analyses of hyper-branched polymers and dendrimers: small-angle neutron scattering, smallangle X-ray scattering, static and dynamic light scattering, NMR relaxation dynamics and scanning probe microscopy (Wataoka et al 1996;Gerle et al 1999;Giotto et al 2001;Sheiko et al 2001Sheiko et al , 2004Lecommandoux et al 2002;Gallyamov et al 2004;Sun et al 2004;Rathgeber et al 2005;Zhang et al 2006;Pietrasik et al 2007). On the other hand, computer simulations of hyper-branched polymers have recently been studied along with the development of theoretical backgrounds and computational technologies (Shiokawa et al 1999;Subbotin et al 2000;Yamakawa and Yoshizaki 2003a, b;Connolly et al 2005;Zhang and Müller 2005;Yethiraj 2006).…”