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

Chen, Jinglu; Xue, Gi; Li, Yanhong; Wang, Lei; Tian, Guohua

doi:10.1021/ma001388l

Cited by 27 publications

(26 citation statements)

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“…12 We also found that the molar volume of solvents plays an important role in the entanglement state of polymer in solution. [13][14][15] Therefore, it is necessary for us to explore the effect of solvent on the conformation of PVC.…”

Section: Introductionmentioning

confidence: 63%

“…In our previous paper, we reported that the PVC sample prepared from very dilute solution in THF was in the expanded state with fewer entanglements which would result a higher crystallinity than samples prepared from more concentrated solution. 12 In the IR spectra shown in Figure 1, the change in relative intensity of the 1427 and 1435 cm -1 bands and the increased intensity of a crystalline bands at 638 cm -1 in curve A indicate that an ordering takes place in PVC due to effect of partly disentanglement of polymer chain in concentrated solution in DOP. PVC freeze-extracted from 5 wt % in DOP has relatively high content of crystalline units, as shown in Figure 1A, while Figure 1B,C illustrates the amorphous morphology of the polymer samples recovered from PVC/THF and PVC/DMP.…”

Section: Resultsmentioning

confidence: 95%

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Crystallization and Relaxation Behavior of Partially Disentangled Poly(vinyl chloride) Prepared from Large Molecule Solvent Dioctyl Phthalate

et al. 2002

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Poly(vinyl chloride) (PVC) samples for the conformation and structural relaxation studies were prepared by freeze-extracting the solutions in various solvents and with varying concentrations. The partially disentangled PVC samples could be obtained by freeze-extracting very dilute PVC/ tetrahydrofuran (THF) and PVC/dimethyl phthalate (DMP) solution (0.05 wt %), while the PVC sample remains in an entangled state after freeze-extracting the concentrated solutions in THF and in DMP. Surprisingly, the extent of interpenetration of PVC chain decreases, even in concentrated solution in dioctyl phthalate (DOP) (5 wt %), which is contrary to accepted theories. DSC and infrared spectroscopic studies showed that a higher ordered conformation could be achieved for the disentangled specimens recovered from concentrated solution in DOP than for the entangled samples prepared from THF and DMP. DSC heating curves showed strong and sharp endothermal peaks for the disentangled polymer after sub-T g annealing. The structural relaxation behavior of the disentangled PVC freeze-extracted from DOP solutions is more predominant, which is in good agreement with the modeling predictions. IntroductionIt is well-known 1 that atactic poly(vinyl chloride) (PVC) is a low crystalline polymer. Commercial PVC contains less than 10% crystalline segments. But this relatively low level of order has a surprisingly significant effect on both its processing and properties. As early as 1926, Flumiani 2 reported that the dispersion state of PVC in the solution could be influenced by temperature, the various heating period, the aging of the solution, the solvent itself, and even the method of preparation of different concentrations of the solution. Despite numerous studies 2-6 dealing with the gelation and aging process of PVC solutions, the mechanism of formation and the structure of PVC physical gel have still not been fully elucidated. It is generally accepted that the cross-links in these gels are tiny crystallites, although according to Guenet et al.,7 hydrogen bonding also plays an important role. Effects of polymerization temperature, 8 heat treatment, 9,10 and processing temperature 11 on crystalline of PVC have been investigated. However, until now, little has been done on the conformation and structural relaxation of PVC affected by solvent because of the complexity of the solvents applied.In our previous work, we prepared partially disentangled PVC samples by the freeze-extraction method from dilute PVC/THF solutions and found that the conformation and relaxation behavior of PVC depended strongly on the entanglements in polymers. 12 We also found that the molar volume of solvents plays an important role in the entanglement state of polymer in solution. 13-15 Therefore, it is necessary for us to explore the effect of solvent on the conformation of PVC. In this work, we selected a normal plasticizer DOP, which has large molar volume, as well as DMP and THF, as the solvents for PVC. Some attempts [16][17][18] have been made to study the extent of...

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Section: Introductionmentioning

confidence: 63%

Section: Resultsmentioning

confidence: 95%

Crystallization and Relaxation Behavior of Partially Disentangled Poly(vinyl chloride) Prepared from Large Molecule Solvent Dioctyl Phthalate

et al. 2002

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“…The results showed that the PVC samples prepared from dilute solutions (<0.25 wt%) were in the expanded state with fewer entanglements, which makes a limited crystallization after annealing of polymer just above T g easier. The structural relaxation rate, observed as a magnitude of the endothermic peak at glass transition, increased with decreasing chain entanglements (i.e., with a lower concentration of initial solution) . Surprisingly, for the same PVC it was discovered that when the solvent was dioctyl phthalate, having a large molecular volume, then the polymer prepared from 5 wt% solution shows similar crystallization behavior as PVC from very dilute solution, suggesting that the extent of chain interpenetration in this concentrated solution was similar to that in the very dilute solutions in THF …”

Section: Properties Of Polymers With Limited Density Of Entanglementsmentioning

confidence: 96%

“…The structural relaxation rate, observed as a magnitude of the endothermic peak at glass transition, increased with decreasing chain entanglements (i.e., with a lower concentration of initial solution). [110] Surprisingly, for the same PVC it was discovered that when the solvent was dioctyl phthalate, having a large molecular volume, then the polymer prepared from 5 wt% solution shows similar crystallization behavior as PVC from very dilute solution, suggesting that the extent of chain interpenetration in this concentrated solution was similar to that in the very dilute solutions in THF. [75] The properties of disentangled materials were studied only for homopolymers, with the exception of Yang's et al work, [165] where the extrusion with injection was used for blending HDPE with 0-10 wt% of commercial, entangled UHMWPE or with synthesized, partially disentangled UHMWPE.…”

Section: Other Observationsmentioning

confidence: 98%

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 this respect a possible role of the entanglement was invoked. It is also worth noting that it has been recently evidenced the influence of the chain entanglements on the structural relaxation features of polycarbonate [36], polystyrene and poly(ether sulfone) [37] and poly(vinyl chloride) [38] with the use of special drying methods [39][40][41] which provide highly disentangled polymeric systems. In particular after annealing the samples in the glass, the enthalpy recovery measured by DSC thermograms showed a quite different behavior for the disentangled systems with respect to the entangled ones.…”

Section: Theoretical Frameworkmentioning

confidence: 99%

Enthalpy recovery in low molecular weight PMMA

Andreozzi

Faetti

Giordano

et al. 2003

Journal of Non-Crystalline Solids

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

Cited by 27 publications

References 28 publications

Crystallization and Relaxation Behavior of Partially Disentangled Poly(vinyl chloride) Prepared from Large Molecule Solvent Dioctyl Phthalate

Crystallization and Relaxation Behavior of Partially Disentangled Poly(vinyl chloride) Prepared from Large Molecule Solvent Dioctyl Phthalate

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

Enthalpy recovery in low molecular weight PMMA

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