Polymer chains, acid-rich

Dendrons attached as side chains on linear polymer chains behave different from free dendrimers and dendrons. Block copolymers, poly(3,5-bis(3,5-bis (benzyloxy)benzyloxy)-benzyl methacrylate-random-methacrylic acid)-block-poly(2-perfluorooctylethyl acrylate), possess poly(benzylether) dendrons and perfluorinated alkyl chains in their side chains (Fig. 4) [85], While an LB film of a copolymer with a medium substitution fraction of poly(benzylether) dendron side chain in poly(methacrylic acid) displays flat surface, a copolymer with high fraction of poly(benzylether) dendron side chains produces the zone texture. Dendron rich blocks are hydrophobic and oleophilic but perfluorinated blocks are solvophobic. Therefore, in this case, the solvophobicity-to-solvophilicity balance must be considered. As a result, copolymers with medium fraction of dendron are laid on solid substrate, but dendron blocks of copolymers with high fraction prefer to arrange at air side of air/ water interface and the fluorocarbon blocks are enforced to exist close to water subphase, resulting in the zone texture [86]. These situations of molecular arrangements at air/water interface are kept even after transfer on solid substrate. By contrast, when perfluorooctadecanoic acids are mixed with block copolymers with high dendron fraction, the flat monolayers are visualized as terrace [87], The monolayers are hierarchized into carboxyl, per-fluoroalkyl, and dendron layers, that is, hydrophilic, solvophobic, and oleophilic layers. In this case, perfluorooctadecanoic acids play a role for ordering of block copolymers. 

Cationic polymerisation employs a strong protic or Lewis acid initiator. A proton, for example, adds to an electron-rich alkene to form the most stable carbocation. The carbocation then adds to another electron-rich alkene to build the polymer chain. The polymerisation is terminated by, for example, deprotonation. 

Since these molecular fragments are produced in a hydrogen-rich environment, they promptly stabilize by hydrogen abstraction from the surrounding hydrocarbon polymer. This process produces dodecane and acid metal sulfide species, in addition to polystyryl radicals. Hydrogen atoms should be principally removed from tertiary carbons in the polymer chains, because in this case resonant-stabilized carbon radicals result ... 

Thiolated polymers, also termed thiomers, are conventional mucoadhesive polymers chemically modified to contain a cysteine residue in the polymer chain and thus establish covalent disulfide bonds with mucin." They can be manufactured to be either cationic (mostly thiolated chitosans) or anionic (carboxylic acid-containing polymers) however, their mucoadhesive extent will mostly be determined by their capacity to covalently bind to mucin. The polypeptide backbone of mucin can be divided into three major subunits tandem repeat array, carboxyl-, and amino-terminal domains. While the amino-terminal domain contains some of the cysteine residues, the carboxyl-terminal domain contains more than 10% of the cysteine residues. These cysteine-rich regions are responsible for forming the large mucin oligomers and ultimately, the groups that allow for the covalent mucoadhesive bond formation with oral mucosal systems." ... 

The application properties of many latexes are strongly affected by the chemistry of the surface of the polymer particles. Relatively small amounts (1-2 wt% based on monomers) of acidic monomers (e.g., acrylic acid, AA) are frequently used in the manufacture of latexes. Because this monomer is water-soluble, upon polymerization, most of the AA-rich polymer chains are located at the surface of the polymer particles. The presence of AA at the surface of the polymer particles is beneficial for both the stability of the latex [11] and the application properties (e.g., both the shear strength of the adhesives [ 12] and the pick strength of coated paper [9] increase with the AA content). In addition, the type and amount of surfactant affects application properties such as colloidal stability and water sensitivity of the film [13]. 

The homopolymers obtained with pure l- or pure D-feed are referred to as polyfL-lactic acid) PLLA) and poly(D-lactic acid) (PDLA), respectively. However, commercial PLA grades are usually based on an L-rich mixture as the majority of bacteria used in fermentation processes mainly produce L-lactic acid and typically comprise a minimum of 1-2% D units [14]. The presence of both L-lactic and D-lactic units in the polymer chain makes PLA a random copolymer as such, its properties are affected by the co-unit content [16,17]. 

The stiffness of the molecular chain of alginates has been compared with other polysaccharides by Smidsrod et al Alginates are found to be stiffer than the similar polymers like carboxymethylcellulose (Brucker et al and Smidsrod et al ). The stiffness is also dependent upon polymer composition and L-guluronic acid rich alginates posses a more rigid chain conformation than D-mannuronic acid rich alginates. The molecular stiffness of the three types of alginate blocks in solution decreases in the order ... 

If polymerized carboxyls are indeed preferentially located in the surface regions of particles, then the expansion model is as follows. At low pH the acid-rich polymer chains remain in a collapsed state until sufficient charge is developed (pH > 8) to cause separation. The attractive forces fall off rapidly as chain separation occurs leading to an abrupt extension. Full extension occurs when all the carboxyls are charged (equivalence point) subsequent addition of sodium hydroxide provides excess electrolyte... 

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