TY - JOUR
T1 - Re-examination of terminal relaxation behavior of high-molecular-weight ring polystyrene melts
AU - Doi, Yuya
AU - Matsumoto, Atsushi
AU - Inoue, Tadashi
AU - Iwamoto, Takuro
AU - Takano, Atsushi
AU - Matsushita, Yushu
AU - Takahashi, Yoshiaki
AU - Watanabe, Hiroshi
N1 - Funding Information:
The authors thank Mr. K. Matsubara and Mr. K. Kinoshita (Nagoya University) for their help of preparation of the high-quality ring polymer samples. The authors highly appreciate thoughtful comments from Prof. D. Vlassopoulos (IESL-FORTH and University of Crete) and Prof. M. Rubinstein (University of North Carolina at Chapel Hill) that helped us to refine this study. This work was partly supported by Grant-in-Aid for Scientific Research (B) (No. 15H03865) from the Japan Society for the Promotion of Science and by the Collaborative Research Program of Institute for Chemical Research, Kyoto University (Grant No. 2015-58). Y.D. (the first author) acknowledges with thanks the financial support from the ACCEL program of the Japan Science and Technology Agency (JST).
Publisher Copyright:
© 2017, Springer-Verlag Berlin Heidelberg.
PY - 2017/6/1
Y1 - 2017/6/1
N2 - For high-molecular-weight (M) ring polymers with low contamination of linear chains, recent viscoelastic tests revealed broad terminal relaxation associated with no clear entanglement plateau. This relaxation behavior is qualitatively similar to that deduced from molecular models (double-folded lattice-animal model and the fractal loopy globule model) for entangled ring polymers, but quantitatively important differences are also noted: For example, the full terminal relaxation of those polymers is slower than the model prediction. This study re-examined the viscoelastic data of entangled high-M ring polystyrene (PS) samples (coded as R-240; M = 244×103) specifically for two points: the purity of the ring samples after the viscoelastic tests and the molecular origin of the stress. For the first point, the R-240 samples contaminated with linear chains at low but different levels were prepared by tuning either the purification efficiency or the retention time of the sample at high temperature (T) before/during the viscoelastic test. The fraction wL of the linear contaminant, determined after the viscoelastic measurement, was ranging from 0.7 to 4.9%, and the extrapolation of the modulus data to wL = 0 gave the data for the ideally pure ring melt. This pure ring melt exhibited broad terminal relaxation that started faster but completed slower compared to the model prediction, indicating that the ring relaxation is not well described by the current model(s) even in the absence of linear contaminant. For the second point, dynamic birefringence measurements were conducted for the R-240 samples with wL = 4.6 and 1.0%. These samples obeyed the stress-optical rule, and their stress-optical coefficient was indistinguishable from that for linear PS samples, revealing that the stress of the ring PS chains reflects the orientational anisotropy of the chains (as is the case also for linear chains). The relaxation behavior of pure ring PS melt is discussed on the basis of these findings, with the focus being placed on the ring-ring threading not considered in the models.
AB - For high-molecular-weight (M) ring polymers with low contamination of linear chains, recent viscoelastic tests revealed broad terminal relaxation associated with no clear entanglement plateau. This relaxation behavior is qualitatively similar to that deduced from molecular models (double-folded lattice-animal model and the fractal loopy globule model) for entangled ring polymers, but quantitatively important differences are also noted: For example, the full terminal relaxation of those polymers is slower than the model prediction. This study re-examined the viscoelastic data of entangled high-M ring polystyrene (PS) samples (coded as R-240; M = 244×103) specifically for two points: the purity of the ring samples after the viscoelastic tests and the molecular origin of the stress. For the first point, the R-240 samples contaminated with linear chains at low but different levels were prepared by tuning either the purification efficiency or the retention time of the sample at high temperature (T) before/during the viscoelastic test. The fraction wL of the linear contaminant, determined after the viscoelastic measurement, was ranging from 0.7 to 4.9%, and the extrapolation of the modulus data to wL = 0 gave the data for the ideally pure ring melt. This pure ring melt exhibited broad terminal relaxation that started faster but completed slower compared to the model prediction, indicating that the ring relaxation is not well described by the current model(s) even in the absence of linear contaminant. For the second point, dynamic birefringence measurements were conducted for the R-240 samples with wL = 4.6 and 1.0%. These samples obeyed the stress-optical rule, and their stress-optical coefficient was indistinguishable from that for linear PS samples, revealing that the stress of the ring PS chains reflects the orientational anisotropy of the chains (as is the case also for linear chains). The relaxation behavior of pure ring PS melt is discussed on the basis of these findings, with the focus being placed on the ring-ring threading not considered in the models.
UR - http://www.scopus.com/inward/record.url?scp=85018841484&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85018841484&partnerID=8YFLogxK
U2 - 10.1007/s00397-017-1014-3
DO - 10.1007/s00397-017-1014-3
M3 - Article
AN - SCOPUS:85018841484
VL - 56
SP - 567
EP - 581
JO - Rheologica Acta
JF - Rheologica Acta
SN - 0035-4511
IS - 6
ER -