Aging Stability of Neoprene Latex. Relation between Cross-Linking and Hydrolysis of Allylic Chlorine

1955 ◽  
Vol 28 (2) ◽  
pp. 628-640
Author(s):  
D. E. Andersen ◽  
Peter Kovacic
Keyword(s):  
Molecular Weight ◽  
Tensile Strength ◽  
Active Sites ◽  
Film Structure ◽  
Polymer Chains ◽  
Active Chlorine ◽  
Cross Linking ◽  
Curing Conditions ◽  
Cross Links ◽  
Hydrolysis Of

Abstract Neoprene polymer chains are cross-linked between active chlorine sites on the chains. There are two types of active sites of different reactivity. It is necessary to use more vigorous curing conditions to actuate the less reactive chlorine. The polymer develops cross-links while aging as a latex as well as during cure, and the decline of tensile strength with latex age may be inversely correlated with the amount of cross-linking during aging. The decline of tensile strength can be prevented by compounding with bis (diethylthiocarbamyl) disulfide. The calculations of the swelling data are not so complete as might be desired, primarily because of difficulty of measuring and interpreting the molecular weight of high-conversion polymers and to some uncertainty in determining μ. It is felt that the qualitative observations are justified, and that they serve to define both the technically important effect of film structure on tensile strength and the mechanism of cure.

scholarly journals Localization of the Transglutaminase Cross-Linking Sites in the Bacillus subtilis Spore Coat Protein GerQ

2006 ◽  
Vol 188 (21) ◽  
pp. 7609-7616 ◽  
Author(s):  
Alicia Monroe ◽  
Peter Setlow
Keyword(s):  
Bacillus Subtilis ◽  
Coat Protein ◽  
Cross Linking ◽  
Spore Coat ◽  
Bacillus Subtilis Spore ◽  
Binding Partners ◽  
Lysine Residues ◽  
Cross Links ◽  
Hydrolysis Of ◽  
Spore Coat Protein

ABSTRACT The Bacillus subtilis spore coat protein GerQ is necessary for the proper localization of CwlJ, an enzyme important in the hydrolysis of the peptidoglycan cortex during spore germination. GerQ is cross-linked into high-molecular-mass complexes in the spore coat late in sporulation, and this cross-linking is largely due to a transglutaminase. This enzyme forms an ε-(γ-glutamyl) lysine isopeptide bond between a lysine donor from one protein and a glutamine acceptor from another protein. In the current work, we have identified the residues in GerQ that are essential for transglutaminase-mediated cross-linking. We show that GerQ is a lysine donor and that any one of three lysine residues near the amino terminus of the protein (K2, K4, or K5) is necessary to form cross-links with binding partners in the spore coat. This leads to the conclusion that all Tgl-dependent GerQ cross-linking takes place via these three lysine residues. However, while the presence of any of these three lysine residues is essential for GerQ cross-linking, they are not essential for the function of GerQ in CwlJ localization.

scholarly journals p-NN′-phenylenebismaleimide, a specific cross-linking agent for F-actin

1978 ◽  
Vol 175 (3) ◽  
pp. 1023-1032 ◽  
Author(s):  
P Knight ◽  
G Offer
Keyword(s):  
Quantitative Analysis ◽  
Sodium Dodecyl Sulphate ◽  
Actin Filaments ◽  
Sodium Dodecyl ◽  
Cysteine Residue ◽  
Cross Linking ◽  
Maximum Value ◽  
Cross Links ◽  
The Cross ◽  
Hydrolysis Of

Covalent cross-links can be inserted between the subunits of F-actin by using p-NN′-phenylenebismaleimide. Cross-linking reaches its maximum value when one molecule of reagent has reacted with each actin subunit. p-NN′-Phenylenebismaleimide reacts initially with a cysteine residue on one subunit, the slower cross-linking reaction involving a lysine residue on a neighbouring subunit. Hydrolysis of the actin-bound reagent limits the extent of cross-linking. Quantitative analysis of the amounts of cross-linked oligomers seen on polyacrylamide gels containing sodium dodecyl sulphate suggests that neither the binding of the reagent to actin nor the formation of cross-links introduces strain into the structure. The cross-links do not join together different F-actin filaments, and evidence is presented that suggests that the cross-links join subunits of the same long-pitched helix.

Mechanically robust, readily repairable polymers via tailored noncovalent cross-linking

Science ◽  
2017 ◽  
Vol 359 (6371) ◽  
pp. 72-76 ◽  
Author(s):  
Yu Yanagisawa ◽  
Yiling Nan ◽  
Kou Okuro ◽  
Takuzo Aida
Keyword(s):  
Molecular Weight ◽  
Polymer Chains ◽  
Cross Linking ◽  
Low Molecular Weight ◽  
Structural Element ◽  
Reasonable Time ◽  
Diffusion Dynamics ◽  
Important Challenge ◽  
Sustainable Societies ◽  
Hydrogen Bonded

Expanding the range of healable materials is an important challenge for sustainable societies. Noncrystalline, high-molecular-weight polymers generally form mechanically robust materials, which, however, are difficult to repair once they are fractured. This is because their polymer chains are heavily entangled and diffuse too sluggishly to unite fractured surfaces within reasonable time scales. Here we report that low-molecular-weight polymers, when cross-linked by dense hydrogen bonds, yield mechanically robust yet readily repairable materials, despite their extremely slow diffusion dynamics. A key was to use thiourea, which anomalously forms a zigzag hydrogen-bonded array that does not induce unfavorable crystallization. Another key was to incorporate a structural element for activating the exchange of hydrogen-bonded pairs, which enables the fractured portions to rejoin readily upon compression.

3'-Arylazido-β-alanyl-2-azido ATP, a Cross-Linking Photoaffinity Label for F1ATPases

1989 ◽  
Vol 44 (11-12) ◽  
pp. 955-958 ◽  
Author(s):  
Hans-Jochen Schäfer ◽  
Gabriele Rathgeber ◽  
Klaus Dose
Keyword(s):  
Molecular Weight ◽  
Micrococcus Luteus ◽  
Photoaffinity Labeling ◽  
Cross Linking ◽  
Photoaffinity Label ◽  
Cross Links

Abstract The synthesis of the 3′-arylazido-2-azido ATP derivative 3′-O-{3-[N-(4-azido-2-nitrophenyl)-amino]propionyl}2-azido-adenosine 5′-triphosphate (2,3′-DiN3ATP) is described. The bifunc­ tional photoreactive ATP analog is characterized spectroscopically. Photoaffinity labeling of F, ATPase from Micrococcus luteus by this analog results in the inactivation of the enzyme and in the formation of higher molecular weight cross-links,

scholarly journals Optimization of the Curing and Post-Curing Conditions for the Manufacturing of Partially Bio-Based Epoxy Resins with Improved Toughness

Polymers ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1354 ◽  
Author(s):  
Diego Lascano ◽  
Luis Quiles-Carrillo ◽  
Sergio Torres-Giner ◽  
Teodomiro Boronat ◽  
Nestor Montanes
Keyword(s):  
Epoxy Resin ◽  
Epoxy Resins ◽  
Polymer Network ◽  
Thermomechanical Properties ◽  
Diglycidyl Ether ◽  
Polymer Chains ◽  
Cross Linking ◽  
Reactive Diluent ◽  
Gel Time ◽  
Curing Conditions

This research deals with the influence of different curing and post-curing temperatures on the mechanical and thermomechanical properties as well as the gel time of an epoxy resin prepared by the reaction of diglycidyl ether of bisphenol A (DGEBA) with an amine hardener and a reactive diluent derived from plants at 31 wt %. The highest performance was obtained for the resins cured at moderate-to-high temperatures, that is, 80 ° C and 90 ° C , which additionally showed a significant reduction in the gel time. This effect was ascribed to the formation of a stronger polymer network by an extended cross-linking process of the polymer chains during the resin manufacturing. Furthermore, post-curing at either 125 ° C   or 150 ° C yielded thermosets with higher mechanical strength and, more interestingly, improved toughness, particularly for the samples previously cured at moderate temperatures. In particular, the partially bio-based epoxy resin cured at 80 ° C and post-cured at 150 ° C for 1 h and 30 min, respectively, showed the most balanced performance due to the formation of a more homogeneous cross-linked structure.

EPDM RUBBER PLASTICIZED WITH POLYMERIC SOYBEAN OIL OF DIFFERENT MOLECULAR WEIGHTS

2017 ◽  
Vol 90 (4) ◽  
pp. 667-682 ◽  
Author(s):  
Zoran S. Petrović ◽  
Jelena Milić ◽  
Mihail Ionescu ◽  
James R. Halladay
Keyword(s):  
Molecular Weight ◽  
Tensile Strength ◽  
Soybean Oil ◽  
Cross Linking ◽  
Tear Strength ◽  
Soybean Oils ◽  
Molecular Weights ◽  
Compression Set ◽  
Diene Rubber ◽  
Processing Aids

ABSTRACT Polymerization of soybean oil produces higher-viscosity liquids, which may serve as processing aids and plasticizers in certain rubbers as a replacement of petrochemical oils. Four polymerized soybean oils of different molecular weights showed good compatibility with ethylene–propylene–diene rubber (EPDM), but because of the presence of double bonds and copolymerization with EPDM, they decreased the cross-linking density when compared with paraffinic extender oil. As a consequence, polymeric soybean oils reduced tensile strength and modulus but increased elongation, tear strength, and compression set. Higher-molecular-weight plasticizers are expected to reduce sweating out of oils. Pure soybean oil was not completely compatible at the concentration tested, but it showed a strong plasticizing effect; dramatically lowered tensile strength, tear strength, and modulus; and increased elongation and compression set. No clear effect of molecular weight of polymerized soybean oils on properties was observed, but increasing the sulfur content was found to be beneficial. Using polymeric vegetable oils instead of petrochemical extenders in EPDM rubbers is economical and environmentally desirable, but the curing system requires optimization to accommodate loss of cross-linking density.

THE ANIONIC POLYMERIZATION OF ALLYL ACRYLATE AND OF ALLYL METHACRYLATE

1966 ◽  
Vol 44 (6) ◽  
pp. 695-702 ◽  
Author(s):  
S. Bywater ◽  
P. E. Black ◽  
D. AM. Wiles
Keyword(s):  
Molecular Weight ◽  
Anionic Polymerization ◽  
Allyl Alcohol ◽  
Polymer Chains ◽  
Cross Linking ◽  
Low Molecular Weight ◽  
Carbonyl Groups ◽  
Double Bonds ◽  
Soluble Product ◽  
Allyl Methacrylate

The low temperature polymerization of allyl acrylate in toluene solution has been investigated with n-butyllithium and 1,1-diphenyl-n-hexyllithium initiators. The latter was also used in a study of the polymerization of allyl methacrylate under the same conditions. The reactions between initiator and monomer were rapid in all cases. More than half of the initiator molecules reacted with monomer acrylic double bonds to start polymer chains, only a few of which grew to a high molecular weight, highly isotactic product. Most of the chains remained as a low molecular weight, precipitant-soluble product. The remaining initiator molecules reacted with the carbonyl groups of the monomers to produce species which could be detected as allyl alcohol, after termination of the reaction with acetic acid. The allyl double bonds were not involved in reactions during polymerization but were presumably responsible for the cross-linking which occurred when the polymers were exposed to air.

scholarly journals Peptidoglycan Cross-Linking Activity of L,D-Transpeptidases from Clostridium difficile and Inactivation of These Enzymes by β-Lactams

2017 ◽  
Vol 62 (1) ◽  
Author(s):  
Laetitia Sütterlin ◽  
Zainab Edoo ◽  
Jean-Emmanuel Hugonnet ◽  
Jean-Luc Mainardi ◽  
Michel Arthur
Keyword(s):  
Mass Spectrometry ◽  
Clostridium Difficile ◽  
Cross Linking ◽  
Content Type ◽  
Catalytic Activities ◽  
Cross Links ◽  
Covalent Adducts ◽  
The Stability ◽  
Hydrolysis Of ◽  
Insight Into

ABSTRACT In most bacteria, the essential targets of β-lactam antibiotics are the d , d -transpeptidases that catalyze the last step of peptidoglycan polymerization by forming 4→3 cross-links. The peptidoglycan of Clostridium difficile is unusual since it mainly contains 3→3 cross-links generated by l , d -transpeptidases. To gain insight into the characteristics of C. difficile peptidoglycan cross-linking enzymes, we purified the three putative C. difficile l , d -transpeptidase paralogues Ldt Cd1 , Ldt Cd2 , and Ldt Cd3 , which were previously identified by sequence analysis. The catalytic activities of the three proteins were assayed with a disaccharide-tetrapeptide purified from the C. difficile cell wall. Ldt Cd2 and Ldt Cd3 catalyzed the formation of 3→3 cross-links ( l , d -transpeptidase activity), the hydrolysis of the C-terminal d -Ala residue of the disaccharide-tetrapeptide substrate ( l , d -carboxypeptidase activity), and the exchange of the C-terminal d -Ala for d -Met. Ldt Cd1 displayed only l , d -carboxypeptidase activity. Mass spectrometry analyses indicated that Ldt Cd1 and Ldt Cd2 were acylated by β-lactams belonging to the carbapenem (imipenem, meropenem, and ertapenem), cephalosporin (ceftriaxone), and penicillin (ampicillin) classes. Acylation of Ldt Cd3 by these β-lactams was not detected. The acylation efficacy of Ldt Cd1 and Ldt Cd2 was higher for the carbapenems (480 to 6,600 M −1 s −1 ) than for ampicillin and ceftriaxone (3.9 to 82 M −1 s −1 ). In contrast, the efficacy of the hydrolysis of β-lactams by Ldt Cd1 and Ldt Cd2 was higher for ampicillin and ceftriaxone than for imipenem. These observations indicate that Ldt Cd1 and Ldt Cd2 are inactivated only by β-lactams of the carbapenem class due to a combination of rapid acylation and the stability of the resulting covalent adducts.

Photoresins based on acrylated epoxidized soybean oil and benzenedithiols for optical 3D printing

2019 ◽  
Vol 25 (2) ◽  
pp. 378-387 ◽  
Author(s):  
Greta Miezinyte ◽  
Jolita Ostrauskaite ◽  
Egidija Rainosalo ◽  
Edvinas Skliutas ◽  
Mangirdas Malinauskas
Keyword(s):  
3D Printing ◽  
Soybean Oil ◽  
Real Time ◽  
Insoluble Fraction ◽  
Polymer Chains ◽  
Epoxidized Soybean Oil ◽  
Cross Linking ◽  
Content Type ◽  
Cross Links ◽  
Acrylated Epoxidized Soybean Oil

Purpose The purpose of this paper is the design and investigation of novel acrylated epoxidized soybean oil-based photocurable systems as candidate materials for optical 3D printing. Design/methodology/approach Aromatic dithiols, benzene-1,3-dithiol or benzene-1,4-dithiol, were used as cross-linking agents of acrylated epoxidized soybean oil in these systems. Kinetics of photocross-linking was investigated by real-time photorheometry using two different photoinitiators, 2, 2-dimethoxy-2-phenylacetophenone or 2-hydroxy-2-methylpropiophenone, in different quantities. The effect of the initial composition on the rate of photocross-linking, mechanical, thermal properties and swelling of obtained polymers was investigated. Findings The rate of photocross-linking was higher, more cross-links and shorter polymer chains between cross-linking points of the network were formed when benzene-1,4-dithiol and 2, 2-dimethoxy-2-phenylacetophenone were used in compositions. The higher yield of insoluble fraction, glass transition temperatures and values of compressive modulus were obtained when benzene-1,3-dithiol and 2, 2-dimethoxy-2-phenylacetophenone were used in compositions. Originality/value This is the first study of acrylated epoxidized soybean oil-based thiol-ene system by real-time photorheometry. The designed novel photocurable systems based on acrylated epoxidized soybean oil and benzenedithiols are promising renewable photoresins for rapid optical 3D printing on demand.

Collagen Cross-linking and Ultimate Tensile Strength in Dentin

2004 ◽  
Vol 83 (10) ◽  
pp. 807-810 ◽  
Author(s):  
P.A. Miguez ◽  
P.N.R. Pereira ◽  
P. Atsawasuwan ◽  
M. Yamauchi
Keyword(s):  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Dental Materials ◽  
Cross Linking ◽  
Anatomical Location ◽  
Dentinal Tubules ◽  
Root Dentin ◽  
Cross Links ◽  
The Difference ◽  
Collagen Cross Linking

Several studies have indicated differences in bond strength of dental materials to crown and root dentin. To investigate the potential differences in matrix properties between these locations, we analyzed upper root and crown dentin in human third molars for ultimate tensile strength and collagen biochemistry. In both locations, tensile strength tested perpendicular to the direction of dentinal tubules (undemineralized crown = 140.4 ± 48.6/root = 95.9 ± 26.1; demineralized crown = 16.6 ± 6.3/root = 29.0 ± 12.4) was greater than that tested parallel to the tubular direction (undemineralized crown = 73.1 ± 21.2/root = 63.2 ± 22.6; demineralized crown = 9.0 ± 3.9/root = 16.2 ± 8.0). The demineralized specimens showed significantly greater tensile strength in root than in crown. Although the collagen content was comparable in both locations, two major collagen cross-links, dehydrodihydroxylysinonorleucine/its ketoamine and pyridinoline, were significantly higher in the root (by ~ 30 and ~ 55%, respectively) when compared with those in the crown. These results indicate that the profile of collagen cross-linking varies as a function of anatomical location in dentin and that the difference may partly explain the site-specific tensile strength.

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