Normale und anomale Gefrierpunktserniedrigung

Kühn, Werner; Majer, Helge

doi:10.1002/ange.19560681002

Cited by 40 publications

(11 citation statements)

References 6 publications

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“…This extended range of influence of network junctions has an analogous effect on crystallization in networks. [45][46][47] Along with the study of segmental dynamics in polymers, microgels offer the possibility of serving as model networks for the study of rubber elasticity. 48 This is an area in which the role of entanglements remains to be quantitatively established, and hence any insights microgels can provide will be welcome.…”

Section: Discussionmentioning

confidence: 99%

Mechanical Behavior of Polystyrene Microgels

Roland¹,

Santangelo²,

Antonietti³

et al. 1999

Macromolecules

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Polystyrene microgels are nanometer-sized particles produced by polymerization and crosslinking in microemulsion. As a result of their internal network structure, microgels have negligible intermolecular entanglement interactions. This can have a profound effect on their rheology; it also leads to glassy fracture resembling the behavior of low molecular weight, linear polystyrene. At higher frequencies, the mechanical response of microgels is quite similar to that of linear polystyrene. Breakdown of time-temperature superpositioning occurs in the softening zone of the viscoelastic spectrum. In the glass transition region, the segmental relaxation function is broadened and exhibits an enhanced dependence on temperature. The latter two effects, due to the cross-linking of the microgels, are also seen in conventional, macroscopic networks.

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Section: Discussionmentioning

confidence: 99%

Mechanical Behavior of Polystyrene Microgels

Roland¹,

Santangelo²,

Antonietti³

et al. 1999

Macromolecules

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“…The principle of the method due to KUEN (2) is that the size of the crystal of the solvent which grows in the swollen vulcanizate is limited in size by the mesh of the network (Fig.l), the resulting freezing point depression AT is therefore related to the …”

Section: Principlementioning

confidence: 99%

Structure of filled and unfilled elastomers: Thermoporometric measurements

Pouchelon¹,

Soria²,

Moll³

1990

Makromolekulare Chemie. Macromolecular Symposia

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The thermoporometry has been applied to the determination of the crosslink density of silicone elastomers. Significant effort was devoted to the choice of the solvent, only the 2-butanone leads to the desired thermoporometric effect. The problem of the physical state of the polymer at the temperature of the experiment was pointed out. Nevertheless, the obtained results expressed by the distribution of the molecular weigth between crosslinks and their average values are compatible with those of the usual techniques and they well explain the mechanical properties of the elastomers. INTRmum1ON

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“…2b-2e). On the other hand, it is known [46,47] that, upon the freezing of single-phase crosslinked gels, the growth of crystals of frozen sol-vent in a mesh of the polymer network of a gel can readily lead to the rupture of weak parts of chains and, hence, to the changes in the gel structure (e.g., such changes caused by cryogenic treatment were revealed in crosslinked polyacrylamide gels by electron microscopy [48]). Upon repeated freezing, the ice is formed first in the cryogel macropores [4]; therefore, the stages of the nucleation of ice and initial growth of its crystals proceed, in this case, in a microenvironment that is not constrained by the presence of polymer network and, in essence, is close to the nucleation and initiation of the growth of crystals of some salts upon their "growth" from supersaturated solutions in the matrix of some low-concentrated gels [44,45].…”

Section: Structure-induced Morphological Peculiarities Of Cryopvags Fmentioning

confidence: 99%

10.1007/s10595-008-2011-0

2000

CrossRef Listing of Deleted DOIs

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Macroporous viscoelastic poly(vinyl alcohol) (PVA) cryogels are prepared from aqueous concentrated (80-120 g/l) PVA solutions subjected to 1-5 cycles of cryogenic treatment (freezing at -20 ° C for 19 h and subsequent thawing at a rate of 0.3 ° C/min). Shear moduli and fusion temperatures of corresponding samples are determined and the structure of thin sections is studied by optical microscopy with subsequent processing and analysis of images obtained. The previously described effect of a substantial increase in the rigidity and thermal stability of PVA cryogels resulted from the repeated freezing-thawing cycles is confirmed. The largest (jumpwise) changes in the physicochemical characteristics of such gels and their macroporous morphology take place after the second cycle of cryogenic treatment. Moreover, depending on the PVA concentration in the initial solution, the mean cross section of micropores increases by a factor of 2-3 and the total porosity of cryogel rises by a factor of 1.5 − 2; i.e., the imperfection of material increases. Nevertheless, this negative (from viewpoint of the integral properties of cryogel) effect is completely overpowered by processes of additional structuring, which result in the strengthening of polymer phase proceeding during the repeated freezing-thawing cycles.

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Normale und anomale Gefrierpunktserniedrigung

Cited by 40 publications

References 6 publications

Mechanical Behavior of Polystyrene Microgels

Mechanical Behavior of Polystyrene Microgels

Structure of filled and unfilled elastomers: Thermoporometric measurements

10.1007/s10595-008-2011-0

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