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.

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.

Calcium-Dependent Cross-Linking Processes in Platelets

1979 ◽  
Author(s):  
I. Cohen ◽  
T. Glaser
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Cross Linking ◽  
Low Molecular Weight ◽  
Tracer Concentration ◽  
Calcium Dependent ◽  
A 23187 ◽  
Polymer Formation ◽  
Total Disappearance ◽  
Low Molecular Weight Proteins

When platelet cytoplasmic Ca2+ is increased by the ionophore A 23187, there is the coincident appearance of a cross-linked polymer and the partial disappearance of five high molecular weight polypeptide bands (> 145,000). The glycoproteins show a partial disappearance of bands lb, IIb and IV and the total disappearance of hands la and Ilia. The disappearance of the protein bands, possibly contributing to the polymer formation, is prevented by histamine, aminoacetonltrile and cystamlne, which, as pseudodonor amines are known Inhibitors of factor XHIa-catalyzed cross-linking. 14C-histamine, at a tracer concentration, was incorporated into the polymer as well as into myosin, glycoproteins IIb and IIIa (α-actinln), actin and two unidentified low-molecular weight proteins. The polymer formed is also apparent in isolated membranes following the iono-phore-stimulated increase in intracellular Ca2+. These findings are unrelated to a proteolytic activity since the platelet Ca2+-dependent proteases are inhibited by leupep-tin. Ca2+-activation of a platelet cytosol transamidase would explain the data obtained. This platelet transamidase(s) may couple membrane proteins to cytoplasmic contra-tlle proteins. Thus, a new concept is proposed for the stabilization of platelet membranes and platelets as they form the hemostatic plug.

scholarly journals Binding Affinity, Cellular Uptake, and Subsequent Intracellular Trafficking of the Nano-Gene Vector P123-PEI-R13

2016 ◽  
Vol 2016 ◽  
pp. 1-8
Author(s):  
Yaguang Zhang ◽  
Hongmei Shu ◽  
Jing Hu ◽  
Min Zhang ◽  
Junweng Wu ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Cellular Uptake ◽  
Intracellular Trafficking ◽  
Transfection Efficiency ◽  
Cross Linking ◽  
Low Molecular Weight ◽  
Gene Vector ◽  
Dna Complexes ◽  
Dynamic Source

A nano-gene vector PEI-P123-R13 was synthesized by cross-linking low molecular weight PEI with P123 and further coupling bifunctional peptide R13 to the polymer for targeting tumor and increasing cellular uptake. The binding assessment of R13 toαvβ3 positive cells was performed by HRP labeling. The internalization pathways of P123-PEI-R13/DNA complexes were investigated based on the effect of specific endocytic inhibitors on transfection efficiency. The mechanism of intracellular trafficking was investigated based on the effect of endosome-lysosome acidification inhibitors, cytoskeleton, and dynein inhibitors on transfection efficiency. The results indicated that the bifunctional peptide R13 had the ability of binding toαvβ3 positive cellsin vitro. The modification of P123-PEI-R13 with R13 made it display new property of internalization. P123-PEI-R13/DNA complexes were conducted simultaneously via clathrin-mediated endocytosis, caveolin-mediated endocytosis, macropinocytosis, and possible energy-independent route. After internalization, P123-PEI-R13/DNA complexes could escape from the endosome-lysosome system because of its acidification and further took microtubule as the track and dynein as the dynamic source to be transported toward the microtubule (+) end, to wit nucleus, under the action of microfilament, and with the aid of intermediate filament.

Ozonolytic Degradation of Interpolymers of Natural Rubber with Methyl Methacrylate and Styrene

1958 ◽  
Vol 31 (1) ◽  
pp. 82-85
Author(s):  
D. Barnard
Keyword(s):  
Molecular Weight ◽  
Carbon Black ◽  
Natural Rubber ◽  
Accurate Determination ◽  
Synthetic Polymers ◽  
Polymer Chains ◽  
Low Molecular Weight ◽  
Rubber Content ◽  
Tert Butyl Hydroperoxide

Abstract The preparation of graft and block interpolymers of natural rubber and synthetic polymers has made it desirable that the number and size of polymer chains attached to rubber be readily determinate. The degradation of unsaturated polymers with tert-butyl hydroperoxide in the presence of osmium tet oxide has been used for the determination of free polystyrene in SBR and carbon black in several elastomers, and has recently been applied to the present problem. The accurate determination of the rubber content of interpolymers by quantitative ozonolysis essentially according to the method of Boer and Kooyman suggested that this might be made the basis of isolation of the attached polymer, the rubber being degraded into fragments of low molecular weight, from which the polymer could be separated by conventional techniques. The method should be applicable to any interpolymer, or mixture, of a polyunsaturated and a saturated polymer and is illustrated with reference to interpolymers of natural rubber (NR)-polymethyl methacrylate (PMM) and NR-polystyrene (PS).

SYNTHESIS AND CHARACTERIZATION OF FARNESENE-BASED POLYMERS

2017 ◽  
Vol 90 (2) ◽  
pp. 308-324 ◽  
Author(s):  
Taejun Yoo ◽  
Steven K. Henning
Keyword(s):  
Molecular Weight ◽  
Anionic Polymerization ◽  
Molar Mass ◽  
Functional Materials ◽  
Synthesis And Characterization ◽  
Low Molecular Weight ◽  
Structure Property ◽  
Structure Property Relationships ◽  
By Products

ABSTRACT A bio-based route to the production of trans-β-farnesene has recently been commercialized. Trans-β-farnesene is capable of being polymerized by both anionic and cationic pathways, creating low molecular weight polymers with structure–property relationships unique within the diene class of monomers. Trans-β-farnesene is produced through fermentation of sugar feedstocks. The pathway offers an alternative to petroleum-based feedstocks derived as by-products of naphtha or ethane cracking. Anionic polymerization of the monomer produces a highly branched “bottlebrush” structure, with rheological properties that are markedly different than those of linear diene polymers. Specifically, a lack of entanglements is observed even at relatively high molar masses. For hydroxyl-terminated oligomers, Tg as a function of molar mass follows a trend opposite non-functional materials. The synthesis and characterization of trans-β-farnesene–based polymers will be presented, including anionically prepared low molecular weight diols and monols.

Etude de quelques polymères obtenus lors de la déshydratation en système statique d'alcools allyliques disubstitués

1973 ◽  
Vol 51 (2) ◽  
pp. 288-291 ◽  
Author(s):  
Claude Roux ◽  
Hubert Daoust
Keyword(s):  
Molecular Weight ◽  
Allyl Alcohol ◽  
Thermal Dehydration ◽  
Low Molecular Weight ◽  
Static System ◽  
Molecular Weights ◽  
Molecular Weight Distributions ◽  
Weight Distributions ◽  
Allyl Alcohols ◽  
Specific Volumes

Diolefins, produced by thermal dehydration of disubstituted allyl alcohols in a static system, polymerize as they are formed giving low molecular weight polymers. The microstructure of the product is similar to that of thermal polymers of 1,3-dienes. Number- and weight-average molecular weights, partial specific volumes, and molecular weight distributions have been studied for the polymers obtained from 3-methyl-2-butene-1-ol and 3,3-dimethyl-allyl alcohol.

scholarly journals Benzil Photoperoxidations in Polymer Films and Crosslinking by the Resultant Benzoyl Peroxides in Polystyrene and Other Polymers

Molecules ◽  
2021 ◽  
Vol 26 (17) ◽  
pp. 5154
Author(s):  
Ivan Lukáč ◽  
Branislav Husár ◽  
Martin Danko ◽  
Richard G. Weiss
Keyword(s):  
Molecular Weight ◽  
Polymer Films ◽  
Glassy Polymer ◽  
Polymer Networks ◽  
Polymer Chains ◽  
Solid Surfaces ◽  
Low Molecular Weight ◽  
Long Wavelength ◽  
Covalently Linked ◽  
Phenyl Vinyl

Benzil (BZ) can be converted almost quantitatively to benzoyl peroxide (BP) in aerated polymer films upon irradiation at >400 nm (i.e., the long-wavelength edge of the n→π* absorption band of BZ, where BP does not absorb). Here, we summarize results for the photoperoxidation of BZ structures with molecular oxygen, principally in glassy polymer matrices. Some of the polymers are doped directly with BZ or its derivatives, and others, contain covalently attached BZ pendant groups from which BP groups are derived. While the decomposition of low-molecular-weight BP doped into polymer films (such as those of polystyrene (PS)) results in a net decrease in polymer molecular weight, thermal decomposition of pendant BP groups is an efficient method for chain crosslinking. Crosslinking of PS films doped with a molecule containing two covalently linked BZ or BP groups proceeds in a similar fashion. Free radicals from the covalently attached BP allow grafting of new monomers, as well. Additionally, the use of radiation filtered through masks has been used to create patterns of polymers on solid surfaces. Crosslinking of photodegradable poly(phenyl vinyl ketone) with BP structures obtained by photoperoxidation of BZ structures for the preparation of photodegradable polymer networks is described as well. In sum, the use of BZ and BP and their derivatives offers simple and convenient routes for modifying polymer chains and, especially, for crosslinking them. Specific applications of each use and process are provided. Although applications with PS are featured here, the methodologies described are amenable to a wide variety of other polymers.

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