Scattering function of semi-rigid cyclic polymers analyzed in terms of worm-like rings: cyclic amylose tris(phenylcarbamate) and cyclic amylose tris(n-butylcarbamate)

Abstract

Recently reported data of the particle scattering function P(q) with the magnitude q of the scattering vector for rigid cyclic amylose tris(phenylcarbamate) (cATPC) and cyclic amylose tris(n-butylcarbamate) (cATBC) in different solvents were analyzed in terms of a novel simulation method based on the Kratky-Porod wormlike chain model. Although similar wormlike chain parameters were evaluated for both relatively flexible cyclic chains and the corresponding linear polymers, an appreciable decrease in the chain stiffness and slight extension of the local helical structure were found for cyclic chains with a higher chain stiffness. The difference in the wormlike chain parameters between the cyclic and linear chains cannot be realized in the previously reported molar mass dependence of the radius of gyration. This suggests that analyses of P(q) are decisively important to understand the conformational properties of rigid and/or semiflexible cyclic chains in solution if the molar mass range of the cyclic polymer samples is limited.

Linear and cyclic amylose derivatives having brush like side groups in solution: Amylose tris(n-octadecylcarbamate)s

“…While P(q) of the wormlike ring cannot be calculated analytically, Tsubouchi et al [64] developed a Monte Carlo simulation method to calculate the particle scattering function Pc(q) of thin wormlike ring. Furthermore, if the chain thickness is taken into account by the touched-bead model as follows, ( ) (9) we reported that the resultant P(q) successfully reproduced the experimental data for the three amylose derivatives, that is, cATPC, cATBC, and cADMPC [24,44]. A curve fitting procedure was examined assuming log-normal molar-mass distribution with Ð = 1.05 and 1.20.…”

“…Recently, we showed that the Kuhn segment number of the ring polymer becomes larger with lowering NK for the corresponding linear chain. The current NK data are plotted along with our recent results [24,44] in Fig. 11.…”

“…They only reproduce the S 2 z data for high Mw region and deviate upward with lowering Mw in MHK and in MTBE, suggesting that the wormlike chain parameters of the cyclic chain are different from those for the corresponding linear chain and/or they may depend on the chain length as depicted in our previous reports. [24,37,44] It should be noted that the chain thickness effect is insignificant in the Mw range investigated if we estimate it as the touched-bead model of which the contribution can be estimated as S 2  = S 2 c + 3db 2 /20 with db being the bead diameter estimated from the P(q) described below.…”

“…Double logarithmic plots of NK,ring against NK,linear for cATODC in MHK (a green diamond), in MTBE (a blue square), and in THF (a red circle). The other symbols are the literature values [24,44] for cADMPC (filled circles), cATPC (filled squares), and cATBC (filled triangles). A solid line, NK,ring = NK,linear.…”

“…On the contrary, cyclic amylose tris(phenylcarbamate) (cATPC) [22,37], cyclic amylose tris(n-butylcarbamate) (cATBC) [23], and cyclic amylose tris(3,5dimethylphenylcarbamate) (cADMPC) [24] have relatively high chain stiffness in solution since the corresponding linear amylose derivatives behave as semiflexible or rigid chain of which chain stiffness depends significantly on the intramolecular hydrogen bonds [38][39][40][41] (Hbonds) and/or H-bonding interactions between polymer and solvent molecules [42,43]. A further surprising finding was that the chain stiffness and/or the local helical structure are not always the same as the corresponding linear chain [24,37,44]. It is however still unclear whether this topologically originated conformational difference depend on the chemical structure of the side groups.…”