Poly rate from

FIGURE 22 Semilog plot of the in vitro rate of hydrolytic chain scission of PCL, poly glycolic acid-co-lactic acid, and a 1 1 blend of the two polymers, demonstrating the use of blends to modify degradation rates. (From Refs. 64 and 65.)... 

Pitt, C. G., Gratzl, M. M., Jeffcoat, A. R., Zweidinger, R., and Schindler, A., Sustained drug delivery systems. II. Factors affecting release rates from poly( e-caprolactone) and related biodegradable polyesters, J. Pharm. Sci.. 68, 1534-1538, 1979. 

Cai et al. [7e] investigated electron and hole transfer in various polynucleotide duplexes and compared them with previous results found for salmon sperm DNA, to examine the effect of base sequence on excess electron and hole transfer along the DNA 71-way at low temperature. Electron and hole transfer in DNA was found to be clearly base sequence dependent. In glassy aqueous systems (7M LiBr glasses at 77 K), excess electron-transfer rates increase in the order polydIdC-polydIdC<salmon testes DNAexcess electron and hole transfer rates increase in the order polyC-polyG<salmon testes DNATransfer distances at 1 min and distance decay constants for electron and hole transfer from base radicals to MX in polynucleotides-MX and DNA-MX at 77 K are derived and compiled in Table 3. This table clearly shows that the electron-transfer rate from donor sites decreases in... 

A large effective cation size should suppress the cation-siloxane coordination, favor the Iree ion pair 3 in reaction 10, and enhance charge separation. The anticipated effects would be values of n approaching 1 in the rate equation 9, greatly enhanced rates of polymerization, and suppressed formation of cyclosiloxanes. Evidence that these effects are achieved is indicated by the effects seen with R4N countercations (35), the lithium cryp-tates (25, 27), and the crown ether-potassium silanolate complexes (39, 40). Additional evidence for the influence of the countercation on the equilibria is seen in deviations of the amounts of oligomer produced in equilibrated poly(dimethylsiloxane) from the normal distribution caused by specific interactions between the potassium silanolate chain ends (37, 38). More de-... 

Data in Table 19 show the variations In the IMM of PMAA molecules (or poly-(acrylic acid), PAA), when these interact with insulin The polymer complex was se rated from the unreacted molecules. The great decrease in intramolecular motions in PMAA macromolecules as compared to those of PAA in polymer complexes with insulin may be due to hydrophobic interactions between methyl groups of PMAA and non-polar grou K of insulin in aqueous PMAA-insuIin solutions. Kinetic characteristics of intermolecular interactions in the polymer-polymer complexes have also been studied by tlK PL methodThe dependence of kinetic parameters of intermolecular interactions on the structure of interacting chains, their length and the chemical nature of bonds in PC has also been investigated... 

In the homogeneous MMA polymerization with 1-32 (Y = CH3)/CuBr/L-9 (R = n-Pen), the rate increased in the order xylene < DMB < DPE,179 probably due to the differences in the dielectric constant and coordination ability of the solvents. With the homogeneous Ru-1 catalyst, the polymerization of MMA was faster in a polar solvent such as CPI2C12 than in toluene.159 A more detailed analysis on solvent effects was carried out by end-capping a polymer radical with hydroxyl-TEMPO, where the radical intermediate was generated from bromide macroinitiators via CuBr/L-4 catalyst.242 A polar solvent such as butyl acetate increases the radical-generation rate from poly(acrylate)s but not from polystyrene. On the other hand, no rate increase was found for both macroinitiators in DMF, which is... 

C2H, C2F, CjH. Ar Prfy(2-hydroxyethyl methacrylate) (Poly(HEMA)) P<release rate from l diogd... 

The poly(vinyl alcohol) (PVOH) used in this study is Elvanol grade HV from DuPont chemicals. The material is derived from poly(vinyl acetate) (PVAc) by hydrolysis and is in powder form as received. The degree of hydrolysis for Elvanol HV is 99.8% (0.2% residual acetate groups). The molecular of the material used in this investigation is Mw =105,600 - 110,000. PVOH films were produced as described elsewhere 14). Samples were drawn in tension at a strain rate of 1.4 x 10 sec to a maximum draw ratio = 3.08 at 22 C. As-cast material has an equilibrium water content of 5.3 wt% at 22 C and 50% relative humidity (RH) giving a Tg value of 3rc. The HOPE is Hoechst unfractionated Hostalen GF 7660, Mw = 1.06x10 M = 1.01x10. Hydrostatic extrudon, with extrusion temperatures from 60-100 C and strain rates from 2.5 x 10 sec tol.4 x 10 sec" was us to vary draw ratio (die size was varied) with a maximum draw ratio Xm = 16. The maximum draw ratios were limited by fracture. 

Proton nuclear magnetic resonance CH NMR) spectra of the thylene unit in poly(ethylene 2,6-hapthalate) (PEN)/poly(ethylene terephthalate) (PET) blends at various dose rates. (From Kim, J. U. N. Y., Kim, O. FI. S., Kim, S. H. U. N., Jeon, H. A. N. Y., Effects of electron beam irradiation poly(ethylene terephthalate) blends. Polymer Engineering and Science 2004, 44(2), 395-405. With permission.)... 

It is found that (R)-Poly-l forms whiskers when slowly cooled from the isotropic phase, as depicted in Fig. 11.3. The observed whiskers of (R)-Poly-l are 5-7 pm in diameter and approximately 100-200 pm in length. The size of the whisker depends not only on the polymer structure including the side chains but also on the cooling rate from the isotropic phase. A large area of the POM micrograph is dark, but the circularly polarized micrograph indicates that the dark area contains many whiskers (Fig. 11.3b). 

Fig. 19.3. Temperature dependence of common logarithm of crystal growth rate from the melt for a variety of crystalline materials Glycreine [1], Li20-2Si02 [9, PBO-2B2O3 [12] and isotactic poly(styrene) [19] (i-PS). Solid lines are best fitting by Arrhenius expression of the molecular transport term...

Kim, J. M., Seo, K. S., Jeong, Y. K., Lee, H. B., Kim, Y. S. Khang, G. 2005. Co-effect of aqueous solubility of drugs and glycolide monomer on in vitro release rates from poly(D,L-lactide-co-glycolide) discs and polymer degradation. Journal of Biomaterials Science-Polymer Edition, 16, 991-1007. 

Song CX, Labhasetwar V, Levy RJ (1996) Modulation of release rates from double-layer poly(lactic-co-glycolic acid) films for periadventital implants in restenosis. Proc Int Symp... 

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