FT-IR Study of Concentration Dependence for Crystallization of Isotactic Polystyrene Arising from Freeze-Drying Dilute Solutions

Xue, Gi; Wang, Y.; Liu, S.; Liao, Yih-Tyan

doi:10.1021/ma00116a043

Cited by 25 publications

(20 citation statements)

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“…Xue et al have found that the coils of the freeze-dried i-PS or freeze-extracted PET from dilute solution were in the expanded state with fewer entanglements which could crystallize upon annealing at a much higher rate than the i-PS or PET prepared from more concentrated solutions. 18,19 To study further the crystallizability of partially disentangled PVC sample prepared from very dilute solution, we also measured the DSC thermograms of PVC samples after annealing. The melting traces in DSC curves for PVC powder reported in the literature were usually broad and featureless, 20 and two or three peaks often appeared in the annealed samples.…”

Section: Resultsmentioning

confidence: 99%

Conformation and Structural Relaxation of Partially Disentangled Poly(vinyl chloride) Prepared by Freeze-Extracting Dilute Solutions

Chen¹,

Xue²,

Li³

et al. 2001

Macromolecules

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The partially disentangled poly(vinyl chloride) (PVC) samples were prepared by freezeextracting from dilute PVC/THF solutions. The conformation of these samples was investigated by infrared and Raman spectroscopy. The structural relaxation behaviors were studied by differential scanning calorimeter (DSC). The results showed that the PVC samples prepared from dilute solutions with concentrations lower than 0.25% were in the expanded state with fewer entanglements. The conformation and structural relaxation of PVC depended strongly on the entanglements in polymers, and the structural relaxation rate increased with decreasing chain entanglements, which is in good agreement with the modeling predictions.

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Section: Resultsmentioning

confidence: 99%

Conformation and Structural Relaxation of Partially Disentangled Poly(vinyl chloride) Prepared by Freeze-Extracting Dilute Solutions

Chen¹,

Xue²,

Li³

et al. 2001

Macromolecules

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“…A half time of isothermal crystallization (at ranges of 120–140 and 190–220 °C) was shorter for samples obtained from dilute solutions (see Figure ) . Also, when iPS was crystallized from disentangled melt a rapid increase of crystallization rate was visible and the final crystallinity was higher when compared to the bulk, fully entangled polymer …”

Section: Properties Of Polymers With Limited Density Of Entanglementsmentioning

confidence: 99%

“…The disentangled polymers after solidification can be used for studies of crystallization from liquid state (melt, solution) or crystallization in the solid state (i.e., cold crystallization). The crystallization from disentangled melt was examined for iPP, sPP, PLA, iPS, PEO, and UHMWPE . Cold crystallization was examined for PC, PET, PEO, and iPS .…”

Section: Properties Of Polymers With Limited Density Of Entanglementsmentioning

confidence: 99%

The Entanglements of Macromolecules and Their Influence on the Properties of Polymers

Pawlak

2019

Macro Chemistry & Physics

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Macromolecules form entanglements, the presence of which determines many of the polymer's properties; in solution, melt, and solid state. In this review, how the properties of polymers (rheological, thermal, and mechanical), depend on the concentration of the entanglements, is discussed. Although a typical polymer is characterized by the equilibrium density of entanglements, there are methods that can be applied for the reduction of this density. The methods used most often include dissolving a polymer and rapid freezing, crystallization during polymerization, and crystallization from a cooled dilute solution. The properties of disentangled polymers are significantly different from the properties of fully entangled polymers. These properties are discussed in relation to their dependence on the density of the entanglements. The disentangled material can be re‐entangled by the annealing of the polymer; however, reaching the equilibrium density of the entanglements is usually a slow process. It means that a polymer may be processed without losing its disentanglements. The properties of the re‐entangled polymer are usually close to the properties of the initial polymer.

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“…In the nearest several decades, the study of the glass transition of single chain polymers was focused with providing a valuable way to understand the glass transition behavior 1–10. The generally accepted characteristic for such interesting single chain systems is short of the chain entanglement.…”

Section: Introductionmentioning

confidence: 99%

Understanding the effect of chain entanglement on the glass transition of a hydrophilic polymer

Lü¹,

Xue²,

Mi³

2010

J of Applied Polymer Sci

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In this article, we report an interesting phenomenon of the glass transition temperature (T g ) deviation of a hydrophilic polymer. Polyacrylamide (PAL) samples with different extents of chain entanglement were prepared by spray drying and solution casting. We found that the glass transition temperature increases as the extent of chain entanglement decreases upon the sub-T g annealing. The water content in the PAL matrix is found with no direct correlation to T g . However, the observation of a faster diffusion process of water in the disentangled PAL matrix offers an evidence of a faster relaxation process of disentangled PAL molecules. The T g increase of the disentangled PAL samples is believed to be associated with the increased molecular interaction during the chain relaxation process upon the sub-T g annealing. A macroscopic evidence is the fact that the density of the hot-laminated samples increases as the extent of chain entanglement decreases. A thermodynamic analysis suggests that enthalpy more than entropy favors an elevated T g of a disentangled hydrophilic polymer upon the sub-T g annealing. We believe that this research provides new understanding of T g of the hydrophilic polymers, which are being extensively used in bio-related studies.

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FT-IR Study of Concentration Dependence for Crystallization of Isotactic Polystyrene Arising from Freeze-Drying Dilute Solutions

Cited by 25 publications

References 1 publication

Conformation and Structural Relaxation of Partially Disentangled Poly(vinyl chloride) Prepared by Freeze-Extracting Dilute Solutions

Conformation and Structural Relaxation of Partially Disentangled Poly(vinyl chloride) Prepared by Freeze-Extracting Dilute Solutions

The Entanglements of Macromolecules and Their Influence on the Properties of Polymers

Understanding the effect of chain entanglement on the glass transition of a hydrophilic polymer

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