Thermoreversible Gelation with Two-Component Mixed Cross-Link Junctions of Variable Multiplicity in Ternary Polymer Solutions

Theoretical scheme is developed to study thermoreversible gelation interfering with liquid–liquid phase separation in mixtures of reactive f-functional molecules R{Af} and g-functional ones R{Bg} dissolved in a common solvent. Formed polymer networks are assumed to include multiple cross-link junctions containing arbitrary numbers k1 and k2 of functional groups A and B of each species. Sol-gel transition lines and spinodal lines are drawn on the ternary phase plane for some important models of multiple cross-link junctions with specified microscopic structure. It is shown that, if the cross-link structure satisfies a certain simple condition, there appears a special molar ratio of the two functional groups at which gelation takes place with a lowest concentration of the solute molecules, as has been often observed in the experiments. This optimal gelation concentration depends on f and g (functionality) of the solute molecules and the numbers k1 and k2 (multiplicity) of the functional groups in a cross-link junction. For cross-links which allow variable multiplicity, special attention is paid on the perfectly immiscible cross-links leading to interpenetrating polymer networks, and also on perfectly miscible cross-links leading to reentrant sol-gel-sol transition. Results are compared with recent observations on ion-binding polymer solutions, polymer solutions forming recognizable biomolecular complexes, polymer/surfactant mixtures, hydrogen-bonding polymers, and hydrophobically-modified amphiphilic water-soluble polymers.

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EXPERIMENTAL VALIDATION OF THE CHARLESBY AND HORIKX MODELS APPLIED TO DE-VULCANIZATION OF SULFUR AND PEROXIDE VULCANIZATES OF NR AND EPDM

Rubber Chemistry and Technology ◽

10.5254/rct.16.83776 ◽

2016 ◽

Vol 89 (4) ◽

pp. 671-688 ◽

Cited By ~ 8

Author(s):

M. A. L. Verbruggen ◽

L. van der Does ◽

W. K. Dierkes ◽

J. W. M. Noordermeer

Keyword(s):

Experimental Validation ◽

Main Chain ◽

Sol Gel ◽

Chain Scission ◽

Cross Linking ◽

Cross Link ◽

Practical Reality ◽

Cross Links ◽

The Cross ◽

Theoretical Considerations

ABSTRACT The theoretical model developed by Charlesby to quantify the balance between cross-links creation of polymers and chain scission during radiation cross-linking and further modifications by Horikx to describe network breakdown from aging were merged to characterize the balance of both types of scission on the development of the sol content during de-vulcanization of rubber networks. There are, however, disturbing factors in these theoretical considerations vis-à-vis practical reality. Sulfur- and peroxide-cured NR and EPDM vulcanizates were de-vulcanized under conditions of selective cross-link and random main-chain scissions. Cross-link scission was obtained using thiol-amine reagents for selective cleavage of sulfur cross-links. Random main-chain scission was achieved by heating peroxide vulcanizates of NR with diphenyldisulfide, a method commonly employed for NR reclaiming. An important factor in the analyses of these experiments is the cross-linking index. Its value must be calculated using the sol fraction of the cross-linked network before de-vulcanization to obtain reliable results. The values for the cross-linking index calculated with sol-gel data before de-vulcanization appear to fit the experimentally determined modes of network scission during de-vulcanization very well. This study confirms that the treatment of de-vulcanization data with the merged Charlesby and Horikx models can be used satisfactorily to characterize the de-vulcanization of NR and EPDM vulcanizates.

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Quasi-Solid Semi-Interpenetrating Polymer Networks as Electrolytes: Part I. Dependence of Physicochemical Characteristics and Ion Conduction Behavior on Matrix Composition, Cross-Link Density, Chain Length between Cross-Links, Molecular Entanglements, Charge Carrier Concentration, and Nature of Anion

The Journal of Physical Chemistry C ◽

10.1021/jp409533r ◽

2013 ◽

Vol 118 (1) ◽

pp. 159-174 ◽

Cited By ~ 16

Author(s):

Nimai Bar ◽

Kota Ramanjaneyulu ◽

Pratyay Basak

Keyword(s):

Polymer Networks ◽

Physicochemical Characteristics ◽

Charge Carrier Concentration ◽

Interpenetrating Polymer Networks ◽

Matrix Composition ◽

Cross Link ◽

Link Density ◽

Conduction Behavior ◽

Cross Links ◽

Cross Link Density

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Recyclable polymer networks containing hydroxyurethane dynamic cross-links: Tuning morphology, cross-link density, and associated properties with chain extenders

Polymer ◽

10.1016/j.polymer.2019.121604 ◽

2019 ◽

Vol 178 ◽

pp. 121604 ◽

Cited By ~ 15

Author(s):

Xi Chen ◽

Lingqiao Li ◽

John M. Torkelson

Keyword(s):

Polymer Networks ◽

Cross Link ◽

Link Density ◽

Cross Links ◽

Chain Extenders ◽

Cross Link Density

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Thermoreversible gelation with ion-binding cross-links of variable multiplicity

The Journal of Chemical Physics ◽

10.1063/1.5096546 ◽

2019 ◽

Vol 150 (17) ◽

pp. 174904

Author(s):

Fumihiko Tanaka ◽

Yoshiyuki Nakagawa ◽

Seiichi Ohta ◽

Taichi Ito

Keyword(s):

Ion Binding ◽

Variable Multiplicity ◽

Thermoreversible Gelation ◽

Cross Links

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Thermally-Induced Shape-Memory Behavior of Degradable Gelatin-Based Networks

International Journal of Molecular Sciences ◽

10.3390/ijms22115892 ◽

2021 ◽

Vol 22 (11) ◽

pp. 5892

Author(s):

Axel T. Neffe ◽

Candy Löwenberg ◽

Konstanze K. Julich-Gruner ◽

Marc Behl ◽

Andreas Lendlein

Keyword(s):

Shape Memory ◽

Shape Memory Effect ◽

Memory Effect ◽

Shape Recovery ◽

Polymer Networks ◽

Water Soluble ◽

Compression Tests ◽

Thermally Induced ◽

Thermomechanical Process ◽

Triple Helices

Shape-memory hydrogels (SMH) are multifunctional, actively-moving polymers of interest in biomedicine. In loosely crosslinked polymer networks, gelatin chains may form triple helices, which can act as temporary net points in SMH, depending on the presence of salts. Here, we show programming and initiation of the shape-memory effect of such networks based on a thermomechanical process compatible with the physiological environment. The SMH were synthesized by reaction of glycidylmethacrylated gelatin with oligo(ethylene glycol) (OEG) α,ω-dithiols of varying crosslinker length and amount. Triple helicalization of gelatin chains is shown directly by wide-angle X-ray scattering and indirectly via the mechanical behavior at different temperatures. The ability to form triple helices increased with the molar mass of the crosslinker. Hydrogels had storage moduli of 0.27–23 kPa and Young’s moduli of 215–360 kPa at 4 °C. The hydrogels were hydrolytically degradable, with full degradation to water-soluble products within one week at 37 °C and pH = 7.4. A thermally-induced shape-memory effect is demonstrated in bending as well as in compression tests, in which shape recovery with excellent shape-recovery rates Rr close to 100% were observed. In the future, the material presented here could be applied, e.g., as self-anchoring devices mechanically resembling the extracellular matrix.

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Linear Dynamic Viscoelasticity of Dual Cross-Link Poly(Vinyl Alcohol) Hydrogel with Determined Borate Ion Concentration

Gels ◽

10.3390/gels7020071 ◽

2021 ◽

Vol 7 (2) ◽

pp. 71

Author(s):

Takuro Taniguchi ◽

Kenji Urayama

Keyword(s):

Vinyl Alcohol ◽

Ion Concentration ◽

Poly Vinyl Alcohol ◽

Relaxation Dynamics ◽

Cross Link ◽

Dynamic Viscoelasticity ◽

Linear Dynamic ◽

Cross Links ◽

Pva Gel ◽

Pva Hydrogel

We investigated the linear dynamic viscoelasticity of dual cross-link (DC) poly(vinyl alcohol) (PVA) (DC-PVA) hydrogels with permanent and transient cross-links. The concentrations of incorporated borate ions to form transient cross-links in the DC-PVA hydrogels (CBIN) were determined by the azomethine-H method. The dynamic viscoelasticity of the DC-PVA hydrogel cannot be described by a simple sum of the dynamic viscoelasticity of the PVA gel with the same permanent cross-link concentration and the PVA aqueous solution with the same borate ion concentration (CB = CBIN) as in the DC-PVA gel. The DC-PVA hydrogel exhibited a considerably higher relaxation strength, indicating that the introduction of permanent cross-links into temporary networks increases the number of viscoelastic chains with finite relaxation times. In contrast, the relaxation frequency (ωc) (given by the frequency at the maximum of loss modulus) for the DC-PVA hydrogel was slightly lower but comparable to that for a dilute PVA solution with the same CB. This signifies that the relaxation dynamics of the DC-PVA hydrogels is essentially governed by the lifetime of an interchain transient cross-link (di-diol complex of boron). The effect of permanent cross-linking on the relaxation dynamics was observed in the finite broadening of the relaxation-time distribution in the long time region.

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Microtubules and microtubule-associated proteins from the nematode Caenorhabditis elegans: periodic cross-links connect microtubules in vitro.

The Journal of Cell Biology ◽

10.1083/jcb.103.1.23 ◽

1986 ◽

Vol 103 (1) ◽

pp. 23-31 ◽

Cited By ~ 35

Author(s):

E J Aamodt ◽

J G Culotti

Keyword(s):

Caenorhabditis Elegans ◽

Apparent Molecular Weight ◽

Cross Link ◽

Nematode Caenorhabditis Elegans ◽

Microtubule Associated Proteins ◽

C Elegans ◽

Associated Proteins ◽

Cross Links ◽

The Cross

The nematode Caenorhabditis elegans should be an excellent model system in which to study the role of microtubules in mitosis, embryogenesis, morphogenesis, and nerve function. It may be studied by the use of biochemical, genetic, molecular biological, and cell biological approaches. We have purified microtubules and microtubule-associated proteins (MAPs) from C. elegans by the use of the anti-tumor drug taxol (Vallee, R. B., 1982, J. Cell Biol., 92:435-44). Approximately 0.2 mg of microtubules and 0.03 mg of MAPs were isolated from each gram of C. elegans. The C. elegans microtubules were smaller in diameter than bovine microtubules assembled in vitro in the same buffer. They contained primarily 9-11 protofilaments, while the bovine microtubules contained 13 protofilaments. The principal MAP had an apparent molecular weight of 32,000 and the minor MAPs were 30,000, 45,000, 47,000, 50,000, 57,000, and 100,000-110,000 mol wt as determined by SDS-gel electrophoresis. The microtubules were observed, by electron microscopy of negatively stained preparations, to be connected by stretches of highly periodic cross-links. The cross-links connected the adjacent protofilaments of aligned microtubules, and occurred at a frequency of one cross-link every 7.7 +/- 0.9 nm, or one cross-link per tubulin dimer along the protofilament. The cross-links were removed when the MAPs were extracted from the microtubules with 0.4 M NaCl. The cross-links then re-formed when the microtubules and the MAPs were recombined in a low salt buffer. These results strongly suggest that the cross-links are composed of MAPs.

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