Endgroups, polymer

Monodisperse Polystyrene Latexes Surface Charge and Number of Sulfate Endgroups/Polymer Molecule (3,5,9)... 

The direct synthesis of block copoljmiers by radical polymerization is an alternative to using preformed blocks with functional endgroups. Polymers with initiator end-groups (3a,3b), with end groups accessible to radical activation polyinitiators (6, 7.)... 

The broader distribution and bimodal character of the semi-contin-uous molecular weight distributions were attributed to the low concentration of monomer present in the particles and the higher probability of branching. For the batch latexes, the number average molecular weight and the number of surface endgroups/polymer mole-... 

Process Vinyl Acetate-Butyl Acrylate Molar Ratio M, xlO n Acid Endgroups/ Polymer Molecule... 

The number-average molecular weight of a polymer may be controlled by offsetting the stoichiometry of two dissimilar mutually reactive difunctional monomers. The polymer will have the same endgroup functionality as that of the monomer used in excess. For a generic polymer made from a difunctional monomer AA with A functional groups and an excess of difunctional monomer BB widt B functional groups, r is defined as... 

Due to the high reaction temperatures required during the last stages of these syntheses, side reactions cannot be avoided. Acetaldehyde, carboxyl endgroups, and vinyl endgroups are formed during PET and PEN synthesis. The formation of 2,2/-oxydiethylene moieties in polymer chains by etherification of hydroxyl endgroups is also a well-known side reaction of EG polyester syntheses.264 These reactions should be carefully controlled since they can exert an important influence on polymer properties such as Ts, mechanical properties, hydrolytic stability, and discoloration. 

Polyesters are not different from other polymers, and any of the characterization methods commonly used in polymer science can obviously be applied to polyesters and provide information on their structure and properties. In this section, some data specific to polyesters—solubility information, COOH and OH endgroup titration, and infrared (IR) and NMR spectra assignments—are briefly summarized. Most of these data originate from the authors laboratory. References are provided on some particular points only. 

Other endgroups can indirectly be quantified by first hydrolyzing the polymer in diluted chloric acid solution and then determining the composition of the compound by HPFC, reverse-phase chromatography, or gas chromatography (GC).45 48... 

The AB polyamides are made from either >-amino acids or cyclic lactams, derivatives of the oj-amino acids (Table 3.1). In these polymers, the amino and acid groups are inherently balanced and the polymer also contains one amino and one acid endgroup. There are a number of different routes available for polymerizing these AB-type polyamides ... 

Melt viscosity is lower dian the one of corresponding linear polymers, but polar endgroups can increase die viscosity by several orders of magnitude. 

Useful information such as the functionality and crystallinity of the polymers can be obtained by using infrared spectroscopy. Elemental analysis is also considered as one of die tools for die characterization of die polymers. Due to die endgroups and incomplete combustion of the carbon, it is common to observe die low-value carbon content than die theoretical one. 

Chemistry (Continued) polyimide, 287-300 polyurethane, 222-236, 546 transition metal coupling, 483-490 Chiral conjugated polymers, 479-480 Chlorinated solvents, 91 Chlorofluorocarbons (CFCs), 201, 205 Chloroformate endgroups, 87 Chloromethylation, 354 Church, A. Cameron, 431 Circular dichroism, 490 Classical catalysts, 433 Clean Air Act of 1990, 201, 205 Clearcoat, 240... 

Endgroup analyses were carried out with an automatic potentiometer. The [-NH2] and [-C00H] were determined simultaneously. The polymer was dissolved in o-cresol/chloroform mixture (70/30), excess alcoholic KOH added and titrated with alcoholic HCl (0.1 N). The inherent viscosities were determined in0.5% solutions... 

The results of the reaction of finely devided powdered polymer (0.1reaction times and temperatures are given in table 1. On some samples both and (/P) have been determined but as the aci and amine endgroup concentrations do not differ much,(M ) = (/P). The... 

In semi-crystalline polymers at least two effects play a role in the diffusion of the reactive endgroups. Firstly, the restriction in endgroup movement due to the lowering of the temperature, which usually follows an Arrhenius type equation. Secondly, the restriction of the molecular mobility as a result of the presence of the crystalline phase whose size and structure changes on annealing. 

If the reaction goes to completion, the polymer molecules will have the form B B, and the final concentration of B endgroups will be [B]o-[A]q. The number average chain length is... 

The factor of 2 appears in this equation because each polymer molecule has two endgroups. A pesky factor of 2 haunts many polymer equations. It factors out in this example, but we are not always so lucky. 

Suppose that the reactivity of the A and B endgroups is independent of the chains to which they are attached. This is a form of the equal reactivity assumption that is needed for almost all analytical solutions to polymer kinetic problems. If it is satisfied, we can ignore the details of the polymerization and just concentrate on the disappearance of the endgroups. For a batch system. 

---