Polymer weight

Figure C2.1.8. Reduced osmotic pressure V l(RTc as a function of the polymer weight concentration for solutions of poly(a-metliylstyrene) in toluene at 25 °C. The molecular weight of poly(a-metliylstyrene) varies...

The Mark-Houwink-Sakurada equation relates tire intrinsic viscosity to tire polymer weight ... 

Polymer Weight of Beads (g) Chloroform (g) Toluene (g) Ethyl Acetate (g) Dimethylformamide (g)... 

Here Ceq is the ethylene concentration equilibrium to the concentration in a gaseous phase, Kp the propagation rate constant, N the concentration of the propagation centers on the catalyst surface, Dpe the diffusion coefficient of ethylene through the polymer film, G the yield of polymer weight unit per unit of the catalyst and y0at, ype are the specific gravity of the catalyst and polyethylene. 

Thus, spray-dried xylan/ESlOO microparticles were produced at different polymer weight ratios dissolved in alkaline and neutral solutions, separately. More precisely, xylan and ESIOO were dissolved in 1 1 and 1 3 weight ratios in 0.6 N NaOH and phosphate buffer (pH 7.4). Then, the suspensions were spray-diied at the feed rate of 1.2 mL/min (inlet temperature of 120°C) using a Biichi Model 191 laboratory spray-dryer with a 0.7 mm nozzle, separately. Cross-linked xylan microcapsules were also coated by ESIOO after spraydrying at the same conditions. 

It was observed that this technique was able to produce microparticles with a mean diameter of approximately 10.17 + 3.02 pm in a reasonable to satisfactory yield depending on the formulation. This value was observed to be higher for the polymer weight ratio of 1 3 (87.00 + 4.25 %), which indicates that ESIOO improves the final result of the spray-drying process. According to the SEM analysis, the polymeric microparticles were shown to be quite similar in shape. Regardless of the formulation, they appeared to be mostly concave and asymmetric (Figure 12). 

Fig. 12. SEM images of 5-ASA-loaded spray-dried xylan and ESIOO microparticles in different polymer weight ratios (Unpublished data).

Figure 4. Entrance region polymer weight fraction (relative to value at the tube centerline) profiles in the tube cross section for a zeroth order reaction and uniform viscosity at GrSc = 10 and = 0.05 and 0.1.

The high permeability of PCL and its copolymers coupled with a controllable induction period prior to polymer weight loss (vide infra) lends itself to the development of delivery devices that are based on diffusion-controlled delivery of the drug during the induction period prior to weight loss. The subsequent biodegradation of the polymer serves the purpose of eliminating the need to recover the spent device. 

FIGURE 8 Cumulative release of methylene blue (o), [1,4 - 14c] succinic acid (a), and polymer weight loss ( ) from polymer discs prepared from 3,9-bis(ethylidene-2,4,8,10-tetraoxaspiro[5,5Jundecane) and a 50 50 mole ratio of trans - cyclohexane dimethanol and 1,6-hexanediol at pH 7.4 and 37°C. Polymer contains 0.1 wt% [1,4 — [succinic anhydride and 0.3 wt% methylene blue. (From Ref. 

Recently, we explored the effect of molecular weight on the pattern and employed post-dewetting processes to alter the shape of the dewetted polymer droplets. Since the viscosity of a polymer solution is nonlinear with respect to concentration and also strongly dependent on polymer weight, we expected a drastic effect. Figure 11.4... 

The polymer weight concentration can then be calculated by multiplying the polymer concentrations by the number of protomers per polymer and then by the protomer molecular weight. Thus we have... 

As noted above, turbidity and polymer weight concentration can be directly related (Cp = or, where t is the turbidity), and the proportionality constant may be determined experimentally (cf. Zackroff et al., 1980). Microtubule protein preparations, however, usually contain a fraction of protein that does not contribute to polymer formation, and the most likely interpretation is that this fraction is composed of assembly-incompetent tubulin and nontubulin protein contaminants (Gaskin et al., 1974 Zackroff et al., 1980). Note that Eq. (30) is based on the assumption that Co represents active, polymerization-competent protomer. If only a fraction y, less than one, is active, this equation must be corrected to give... 

Fig. 6. Determination of the critical protein concentration. (A) Plot of protein in the supernatant fluid after quantitatively sedimenting polymer from a polymerized solution of tubules and tubulin at steady state. The critical concentration, Ko, is determined from the value of the y axis intercept, and the fraction of active protein, y, from the slope. (B) The conventionally used experimental method for estimating the critical concentration. Note that the x axis intercept is actually Ko/y, instead of Kj,. Interpretation of the slope from such plots requires knowledge of the ratio of polymer weight concentradon to turbidity (given here as a). Data from experiments such as those in A may be used in conjunction with this plot to obtain the cridcal concentration, and this can serve as an internal test for self-consistency of the data.

The summations are made over all polymer lengths from one to a maximal length m and typically represents the polymer weight concentration i.e., the total amount of monomer present as polymeric species. Thus the two summations are alternate expressions of [P], the approximate concentration of polymer ends. At equilibrium, dX/dt = 0, and the dissociation constant (K = kofilkon) reduces to [X], which is the concentration of monomer that coexists with polymer at equilibrium. We chose to use the infinity sign as a subscript to distinguish this equilibrium concentration of monomer (i.e., [M]oo) from that concentration [M] that may be present at any other extent of reaction. 

We can consider three situations (a) if [M]oo > [M] , there will be a net increase in polymerization (b) if [M] < [M]oo, there will be net depolymerization and (c) when [M] = [M] , the monomer and polymer are in equilibrium. The last case does not imply a static condition rather, monomer addition and loss can constantly occur, but the total polymer weight concentration will always remain unchanged. In head-to-tah polymerizations, hke those of actin and tubulin assembly in vitro, each of the two polymer ends can interact with monomer the critical concentration [M]o then equals (koff +... 

Johnson and Borisy first showed that the lag phase in the plot of turbidity (i.e., polymer weight concentration) versus time accounted for only 5—10% of the entire amplitude obtained upon completion of the polymerization process. By fitting the elongation phase to a single exponential process, these investigators arrived at the correct conclusion that microtubule number concentration becomes relatively stable within the first minutes... 

Lower-molecular Lower-molecular weight polymer weight macroradical... 

For thermal stability polypyromellitimides are somewhat inferior to polyimides based on the anhydrides of other aromatic tetracarboxylic acids. This is apparently due to the higher chlorine content per unit polymer weight in the former. 

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