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Title: Acceleration or Retardation to Crystallization if Liquid-Liquid Phase Separation Occurs: Studies on a Polyolefin Blend by SAXS/WAXD DSC and TEM

Abstract

Blends of statistical copolymers containing ethylene/hexene (PEH) and ethylene/butene (PEB) exhibited the behavior of upper critical solution temperature (UCST). The interplay between the early and intermediate stage liquid-liquid phase separation (LLPS) and crystallization of the PEH/PEB 50/50 blend was studied by time-resolved simultaneous small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) techniques. Samples were treated by two different quench procedures: in single quench, the sample was directly quenched from 160 C to isothermal crystallization temperature of 114 C; while in double quench, the sample was firstly quenched to 130 C for 20 min annealing, where LLPS occurred, and then to 114 C. It was found that in the early stage of crystallization, the integrated values of Iq2 and crystallinity, Xc, in the double quench procedure were consistently higher than those in the single quench procedure, which could be attributed to accelerated nucleation induced by enhanced concentration fluctuations and interfacial tension. In the late stage of crystallization, some morphological parameters were found to crossover and then reverse, which could be explained by retardation of lamellar growth due to phase separation formed during the double quench procedure. This phenomenon was also confirmed by DSC measurements in blends of different compositions atmore » varying isothermal crystallization temperatures. The crystal lamellar thickness determined by SAXS showed a good agreement with TEM observation. Results indicated that the early stage LLPS in the PEH/PEB blend prior to crystallization indeed dictated the resulting lamellar structures, including the average size of lamellar stack and the stack distribution. There seemed to be little variation of lamellar thickness and long period between the two quenching procedures (i.e., single quench versus double quench).« less

Authors:
; ; ; ; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
959874
Report Number(s):
BNL-82860-2009-JA
Journal ID: ISSN 0032-3861; POLMAG; TRN: US201016%%1018
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Polymer; Journal Volume: 48
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ACCELERATION; ANNEALING; COPOLYMERS; CRYSTALLIZATION; DISTRIBUTION; FLUCTUATIONS; NUCLEATION; POLYOLEFINS; QUENCHING; SCATTERING; THICKNESS; X-RAY DIFFRACTION; national synchrotron light source

Citation Formats

Niu,Y., Wang, Z., Avila Orta, C., Xu, D., Wang, H., Shimizu, K., Hsiao, B., and Han, C. Acceleration or Retardation to Crystallization if Liquid-Liquid Phase Separation Occurs: Studies on a Polyolefin Blend by SAXS/WAXD DSC and TEM. United States: N. p., 2007. Web. doi:10.1016/j.polymer.2007.08.060.
Niu,Y., Wang, Z., Avila Orta, C., Xu, D., Wang, H., Shimizu, K., Hsiao, B., & Han, C. Acceleration or Retardation to Crystallization if Liquid-Liquid Phase Separation Occurs: Studies on a Polyolefin Blend by SAXS/WAXD DSC and TEM. United States. doi:10.1016/j.polymer.2007.08.060.
Niu,Y., Wang, Z., Avila Orta, C., Xu, D., Wang, H., Shimizu, K., Hsiao, B., and Han, C. Mon . "Acceleration or Retardation to Crystallization if Liquid-Liquid Phase Separation Occurs: Studies on a Polyolefin Blend by SAXS/WAXD DSC and TEM". United States. doi:10.1016/j.polymer.2007.08.060.
@article{osti_959874,
title = {Acceleration or Retardation to Crystallization if Liquid-Liquid Phase Separation Occurs: Studies on a Polyolefin Blend by SAXS/WAXD DSC and TEM},
author = {Niu,Y. and Wang, Z. and Avila Orta, C. and Xu, D. and Wang, H. and Shimizu, K. and Hsiao, B. and Han, C.},
abstractNote = {Blends of statistical copolymers containing ethylene/hexene (PEH) and ethylene/butene (PEB) exhibited the behavior of upper critical solution temperature (UCST). The interplay between the early and intermediate stage liquid-liquid phase separation (LLPS) and crystallization of the PEH/PEB 50/50 blend was studied by time-resolved simultaneous small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) techniques. Samples were treated by two different quench procedures: in single quench, the sample was directly quenched from 160 C to isothermal crystallization temperature of 114 C; while in double quench, the sample was firstly quenched to 130 C for 20 min annealing, where LLPS occurred, and then to 114 C. It was found that in the early stage of crystallization, the integrated values of Iq2 and crystallinity, Xc, in the double quench procedure were consistently higher than those in the single quench procedure, which could be attributed to accelerated nucleation induced by enhanced concentration fluctuations and interfacial tension. In the late stage of crystallization, some morphological parameters were found to crossover and then reverse, which could be explained by retardation of lamellar growth due to phase separation formed during the double quench procedure. This phenomenon was also confirmed by DSC measurements in blends of different compositions at varying isothermal crystallization temperatures. The crystal lamellar thickness determined by SAXS showed a good agreement with TEM observation. Results indicated that the early stage LLPS in the PEH/PEB blend prior to crystallization indeed dictated the resulting lamellar structures, including the average size of lamellar stack and the stack distribution. There seemed to be little variation of lamellar thickness and long period between the two quenching procedures (i.e., single quench versus double quench).},
doi = {10.1016/j.polymer.2007.08.060},
journal = {Polymer},
number = ,
volume = 48,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • No abstract prepared.
  • The concentration fluctuations in a poly(2-chlorostyrene)/polystyrene (P2ClS/PS) blend and their changes induced by temperature jumps were studied using time-resolved synchrotron small-angle X-ray scattering (SAXS). The virtual structure factor, which represents a formal extension of the one-phase equilibrium structure factor into the two-phase region, has been obtained from the mean-field static susceptibilities measured in the one-phase region. Three sets of measurements at different jump temperatures (from 140C to 156.87C, to 166.96C, and then to 179.91C) were performed. In the metastable region (142-167C) the experiments indicate that the initial kinetics can be described by the theory developed by Binder, with relaxation timesmore » of chain molecules being in a scale of minutes. The values are comparable with the results of the self-diffusion coefficient (on the order of [approximately]10[sup [minus]15] cm[sup 2]s[sup [minus]1]) of poly(bromostyrene)/polystyrene blends measured in the molten state. In the small scattering wave vector q range the initial relaxation rates of concentration fluctuations increased with increasing q in accordance with theoretical predictions. However, the relaxation process did not clearly follow a simple exponential law. The relaxation rate became slower with increasing time. In the case of a deeper jump (at 179.91C), the relaxation rate changed its sign from positive to negative, with the concentration fluctuations growing and eventually leading to phase separation.« less
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  • The crystallization behavior of isotactic propylene-1-hexene (PH) random copolymer having 5.7% mole fraction of hexene content was investigated using simultaneous time-resolved small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) techniques. For this copolymer, the hexene component cannot be incorporated into the unit cell structure of isotactic polypropylene (iPP). Only {alpha}-phase crystal form of iPP was observed when samples were melt crystallized at temperatures of 40 C, 60 C, 80 C, and 100 C. Comprehensive analysis of SAXS and WAXD profiles indicated that the crystalline morphology is correlated with crystallization temperature. At high temperatures (e.g., 100 C) the dominant morphologymore » is the lamellar structure; while at low temperatures (e.g., 40 C) only highly disordered small crystal blocks can be formed. These morphologies are kinetically controlled. Under a small degree of supercooling (the corresponding iPP crystallization rate is slow), a segmental segregation between iPP and hexene components probably takes place, leading to the formation of iPP lamellar crystals with a higher degree of order. In contrast, under a large degree of supercooling (the corresponding iPP crystallization rate is fast), defective small crystal blocks are favored due to the large thermodynamic driving force and low chain mobility.« less