Carboxylic acid end groups

Ethoxylation of the carboxylic acid end groups of aliphatic polyesters significantly changes the biodegradation rate as well as the crystallinity of these materials (41). 

An implication of the kinetic analysis presented in Sec. IV.A is that the rate of chain scission of polyesters can be retarded by endcapping to reduce the initial carboxylic acid end-group concentration. Alternatively, the rate may be increased by acidic additives that supplement the effect of the carboxy end groups. The first expectation was confirmed by partial ethanolysis of high molecular weight... 

Several studies have dealt with the problem of discriminating between mastic and dammar, and three marker compounds of mastic have been identified moronic, masticadienonic and acetyl masticadienolic acids [42], The chemical structure of (iso)masticadienonic acid and 3-0-acetyl-3-epi(iso)masticadienonic acid is characterized by a side chain, as for dammarane molecules, but with a carboxylic acid end group (Table 12.1). Under pyrolysis conditions this side chain is susceptible to cleavage as demonstrated by the presence, among the pyrolysis products of mastic, of 2-methyl-pent-2,4-dienoic acid, that perfectly matches with the chemical structure of the side chain end. In addition 3-(9-acetyl-3-epi-(iso)masticadienolic acid also loses the acetyl group and, in contrast to masticadienonic acid, is not detected at all. 

Predictions made by Mansfield et al. regarding the surface behaviour of dendrimers were confirmed by Tsukruk et al. who used poly(amidoamine) (PAMAM) dendrimers (generations G3.5-G10) to construct self-assembled monolayers (SAMs) [34,35]. PAMAMs of two adjacent generations with surface amine and carboxylic acid end-groups, respectively, were used in an electrostatic... 

A complicating feature of PBT chemistry is the degradation of hydroxybutyl end groups via a reaction which results in the formation of THF and carboxylic acid end groups. This reversion is often called a backbiting reaction ... 

PBT has both hydroxy and carboxylic acid end groups, and it often contains active residual catalyst (usually titanium based). The resin is still capable of reacting, and molecular weight may be increased by solid-state polymerization. 

The chemical reaction between glycidyl methacrylate (GMA) end groups on the reactive elastomer and the carboxylic acid end groups of PET is shown in... 

The size of dendritic polymers in solution has been shown to be greatly affected by solution parameters such as polarity and pH. Newkome et al., for example, have shown that the size of dendrimers with carboxylic acid end groups in water can be increased by as much as 50% on changing the pH [112]. 

Functionalization can, of course, also be carried out in solution, e.g., in te-trahydrofuran. In this case, temperature control is much easier and the problem of undesired condensation in the functionalization step is reduced. The viscosity increase due to the stronger hydrogen bondings of the formed carboxylic acid end groups is not of importance in the modification step in solution as viscosity can be adjusted through the amount of solvent. Nevertheless, complete solvent removal afterwards sometimes turns out to be laborious. 

Unfunctionalized, i.e., 2-hydroxypropylamide functional, hyperbranched polyesteramides have been tested in powder coating formulations together with stoichiometric (OH/COOH) amounts of acidic polyesters (Uralac). It was anticipated that the reaction of the hydroxyl end groups of the polyesteramide with the carboxylic acid end groups of the polyester would provide a well-crosslinked film with good mechanical properties by polymer/polymer cure. 

Observations Poly-a-glutamic acid containing amine and carboxylic acid end groups... 

Polypropylene imine) dendrimers (see Scheme 1 for structure) have been constructed step by step onto an amine functionalized polystyrene [38, 130, 131]. The challenge in this synthesis is finding conditions for the polypropylene imine) synthesis under which the low MW polystyrene (MW=3200) is soluble [38]. Similar poly(imine) dendrimers with carboxylic acid end groups have also been prepared [130]. The polypropylene imine) dendrimer has also been synthesized on an amino-terminated poly(2-methyl-2-oxazoline) [132]. 

Poly(s-caprolactone) Poly(e-caprolactone) is a semicrystalline polymer synthesized by anionic, cationic, free-radical, or ring-opening polymerization [94]. It is available in a range of molecular weights and degrades by bulk hydrolysis autocatalyzed by the carboxylic acid end groups. The presence of enzymes such as protease, amylase, and pancreatic lipase accelerates polymer degradation [95], The various methods of preparation of poly(e-caprolactone) nanoparticles include emulsion polymerization, interfacial deposition, emulsion-solvent evaporation, desolvation, and dialysis. These methods and various applications are extensively reviewed [94],... 

Polymerization could be terminated by several mechanisms. Cycliza-tion of the growing oligomer terminates chain growth. Reaction of the reactive chain ends with water resulted in the formation of hydroxyl (tetrahydrothiophenium ring termini) and carboxylic acid end groups. 

Tuning to increase solubility of some non-fluorous compounds in fluorous media has recently been reported. Krytox, a commercially available poly(per-fluoroether) lubricant, has a carboxylic acid end group and when this is added to an FC-72 phase, extraction of substituted pyridines is enhanced.This has been attributed to the formation of a hydrogen bond complex. This study shows that non-covalent interactions can be used in modifying the fluorous phase and tailoring its properties for a particular separation. 

Goodings [38] used ethylene dibenzoate as a model compound for pyrolysis studies on PET. His results indicated that an important pyrolytic reaction in molten PET is cleavage of an internal ester linkage to form a carboxylic acid end group and a vinyl ester end group... 

This interpretation was recently shown to be erroneous [66]. No evidence exists for the reversible dissociation, though there is little doubt that at elevated temperatures ester linkages can cleave to form carboxylic acid end-groups and vinyl esters (Section 5.2). 

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