TY - JOUR

T1 - Conformations of Ring Polystyrenes in Bulk Studied by SANS

AU - Iwamoto, Takuro

AU - Doi, Yuya

AU - Kinoshita, Keita

AU - Ohta, Yutaka

AU - Takano, Atsushi

AU - Takahashi, Yoshiaki

AU - Nagao, Michihiro

AU - Matsushita, Yushu

PY - 2018/2/27

Y1 - 2018/2/27

N2 - We prepared five pairs of hydrogenous and deuterated ring polystyrene samples over a wide range of molecular weights (10 kg/mol ≤ Mw ≤ 400 kg/mol) and investigated their chain conformations in bulk by small-angle neutron scattering (SANS) measurements. From the SANS profiles obtained, we estimated the radii of gyration Rg of the ring polymers by the Guinier approximation. Rg can be related to the degree of polymerization N as Rg ∼ N0.47. This scaling exponent ν = 0.47 ± 0.01 is evidently smaller than that for the Gaussian chains (ν = 0.50) but higher than previous experimental reports (ν = 0.42-0.43). Then our data were compared with various simulation and experimental data by introducing the entanglement degree of polymerization Ne for linear polymers as a normalized parameter. Rg of three smaller rings, i.e., R-10, R-30, and R-70, where the numbers denote molecular weights in kg/mol unit, are in good agreement with simulation results, while two larger rings, R-100 and R-400, exhibit higher Rg values than the simulations. Considering that the latter two higher molecular weight samples include maximum 3% of linear contamination, their effects on chain dimension were calculated. As a result, it has been confirmed that 3% of linear contaminations can overestimate Rg of rings as much as 6% for R-100 and 12% for R-400. Thus, Rg for pure large rings should be considerably lower than the present experimental values. We conclude Flory's exponent v in Rg ∼ Nv for rings may not be constant but rather show molecular weight dependence due to their topological constraint.

AB - We prepared five pairs of hydrogenous and deuterated ring polystyrene samples over a wide range of molecular weights (10 kg/mol ≤ Mw ≤ 400 kg/mol) and investigated their chain conformations in bulk by small-angle neutron scattering (SANS) measurements. From the SANS profiles obtained, we estimated the radii of gyration Rg of the ring polymers by the Guinier approximation. Rg can be related to the degree of polymerization N as Rg ∼ N0.47. This scaling exponent ν = 0.47 ± 0.01 is evidently smaller than that for the Gaussian chains (ν = 0.50) but higher than previous experimental reports (ν = 0.42-0.43). Then our data were compared with various simulation and experimental data by introducing the entanglement degree of polymerization Ne for linear polymers as a normalized parameter. Rg of three smaller rings, i.e., R-10, R-30, and R-70, where the numbers denote molecular weights in kg/mol unit, are in good agreement with simulation results, while two larger rings, R-100 and R-400, exhibit higher Rg values than the simulations. Considering that the latter two higher molecular weight samples include maximum 3% of linear contamination, their effects on chain dimension were calculated. As a result, it has been confirmed that 3% of linear contaminations can overestimate Rg of rings as much as 6% for R-100 and 12% for R-400. Thus, Rg for pure large rings should be considerably lower than the present experimental values. We conclude Flory's exponent v in Rg ∼ Nv for rings may not be constant but rather show molecular weight dependence due to their topological constraint.

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U2 - 10.1021/acs.macromol.7b02358

DO - 10.1021/acs.macromol.7b02358

M3 - Article

AN - SCOPUS:85042704964

VL - 51

SP - 1539

EP - 1548

JO - Macromolecules

JF - Macromolecules

SN - 0024-9297

IS - 4

ER -