Type A polymer

Chiral synthetic polymer phases can be classified into three types. In one type, a polymer matrix is formed in the presence of an optically pure compound to moleculady imprint the polymer matrix (Fig. 10) (107,108). Subsequent to the polymerisation, the chiral template is removed, leaving the polymer matrix... 

Anderson RA, Broadhurst CL, Polansky MM, Schmidt WF, Khan A, Flanagan VP, Schoene NW, Graves DJ. 2004. Isolation and characterization of polyphenol type-A polymers from cinnamon with insulin-like biological activity. J Agric Food Chem 52 65-70. 

Watanabe H (2001) Dialectric relaxation of type-A polymers in melts and solutions. Macro-mol Rapid Commun 22(3) 127-175... 

Figure 8. Scheme showing (a) the monomer of els-1,4-poly isoprene and (b) a type-A polymer, having a dipole moment related to the end-to-end distance of the polymer chain. 

Figure 9. Concentration dependence of microviscosities and Brookfield viscosities of unneutralized type A polymer...

Schematically shown in Fig. 5 is the preparation of an enzyme mimic for the hydrolysis of ester 6 by molecular imprinting. Phosphonate 5 is an analog of the transition state for the alkaline hydrolysis of Ester 4. It was used as a template for polymerization with two equivalents of the binding-site monomer iVJV -diethyl-4-vinyl-benzamidine. Amidinium groups were chosen, because they can interact electrostatically with the side carboxyl-ate group as well as with the anionic transition state of the alkaline hydrolysis, thus achieving substrate recognition and transition-state stabilization. Polymerization of the preassembled binding-site monomer with the template (Fig. 5A) followed by template removal (Fig. 5B) leaves a cavity that acts as transition-state receptor for the ester substrate (Fig. 5C). The imprinted polymer accelerates the hydrolysis of 6 more than 100-fold compared to the reaction at the same pH in buffer solution without the polymer. The reaction kinetics is of the Michaelis-Menten type. A polymer obtained with amidinium benzoate as a control, with a statistical distribution of amidinium groups, is ca. one order of magnitude less active in the hydrolysis of 6.

Transfer to polymer can be studied particularly well by adding comparatively low-molecular-weight polymers of the same type (a-polymers) to the polymerizing monomer mixture. The transfer const nt Cp iy can then be calculated from the degrees of polymerization X or found for polymerizations with and without the addition of these a-polymers ... 

A.3. The Normal-Mode (n) Relaxation Process The term normalmode relaxation refers to the long-range motions of the end-to-end dipole moment vector along a polymer chain, and thus corresponds to the comparably slow motion of a whole chain (Adachi 1997). This relaxation mode is characteristic of polymers with dipoles fixed parallel to the mainchain (type A polymers). A representative class of such polymers are the polyethers (-CH2—CHR—O—) , with R H [e.g., poly(propylene glycol) (Hayakawa and Adachi 2001) poly(butylene oxide) (Casalini and Roland 2005)], for which, with the exception of a few members [e.g., poly(styrene oxide) (Hirose and Adachi 2005)], a strong normal-mode relaxation signal can be resolved... 

The dissolution of the polymer component of an erodible implant system for drug delivery may be achieved in two ways. For the Type A polymer matrix, the soluble hydrolytic products remain macromolecular. An example of such a polymer is poly(vinyl acetate) which can be de-acetylated to give the water-soluble poly(vinyl alcohol). In the Type B scheme, the matrix is degraded into low molecular weight fragments like in the ester hydrolysis of polycaprolactone. Previous work in this... 

Dielectric studies on type-A polymers readily yield four sorts of information. First, the strength of the dielectric relaxation reveals the polymer s mean-square end-to-end distance (r ). Second, the relaxation time of the longest-Uved mode corresponds to the correlation time for reorientation of the end-to-end vector. Third, the detailed lineshape of the dielectric relaxation gives information about more complex relaxations. Fourth, by examining copolymers in which all monomers do not have the same dipole moment, one can in principle gain information on polymer internal modes. 

X depend much more strongly on c (a increasing 30-fold when c is increased from 5.2 to 118 g/1, while x falls from 1.7 to 1.26 over the observed c). These behaviors are quite similar to those observed for poly-cw-isoprene, but in a very different polymeric system, arguing that the phenomenology is generally characteristic of type-A polymers in solution and does not reflect specific chemical effects. 

Normal mode descriptions can be compared with experiment. Each normal mode makes a contribution to the dielectric relaxation strength determined by its eigenvector and by the 0j. For a simple type-A polymer, the dielectric moment is determined by the polymer end-to-end vector. This vector relaxes along two paths. In large part, the end-to-end vector relaxes by changing its direction via whole-chain... 

Independent of the significance of normal mode behavior is the use of normal or collective coordinates to describe polymer motion. For example, with a simple type-A polymer in which all monomer dipoles are inserted parallel to each other, the net dipole moment can be represented as proportional to a collective variable, the end-to-end vector ryv - ro. Collective coordinates supply sets of 3A -I- 3 collective variables, all vectors that are properly normalized and orthogonal, with no intent of claiming that they correspond to normal modes of motion or are eigenvectors of some linearized problem. 

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