Poly gels molecular weight dependence

Rotstein et al. included polystyrene (PS) as a probe polymer in poly(vinyl methyl ether) that is with a network chain concentration of 0.235 g/ml and is swollen by toluene. They measured the diffiision coefficient of PS, Dps, using the dynamic light scattering technique and obtained the results as shown in Fig. 15 [15]. The slope of this plot is —2.8. Similarly, the slope for the gel with network chain concentration of 0.200 g/ml was —2.7. These values for molecular weight dependence are larger than expected in a reptation region of —2. This was explained as due to the distribution of network size and the fact that the probe polymer localized near the entropically stable large networks. When the ratio r of... 

Poly(acrylamide) and its acrylic acid copolymers were obtained from polymerization of the monomers in aqueous solution using ammonium persulfate/sodium bisulfite initiator following the procedure reported by Fong and Kowalski.5 Depending on the amount of initiator used, the average molecular weights of the polymers were between 6,000 to 50,000 as determined by gel permeation chromatography (GPC). Taurine (2-aminoethanesulfonic acid) and sodium formaldehyde bisulfite were purchased from Aldrich and used without purification. 

As mentioned above, the preparation of nanogels by addition reactions of functional macromolecular precursors is mainly used for biomedical applications. Thus, the choice of synthetic precursors for microgel formation is restricted to biocompatible materials. Moreover, as most applications are in drug delivery, the molecular weight of the gel precursors should be below the threshold for renal clearance, a value that depends on the molecular architecture and chemical nature of the polymer but that is usually smaller than 30kDa, which is set as the limit for linear PEG [97], Polymers that are mostly used and thus presented in more detail here are PEG, poly(glycidol) (PG), and polyethylene imine) (PEI). 

Polymerization of 2-triethylsilyl-l, 3-butadiene initiated by n-butyl-lithium in hexane yielded (E)-l, 4-poly(2-triethylsilyl-l, 3-butadiene). The molecular weight distribution (as determined by gel permeation chromatography) of the polymers depended on the ratio of monomer to initiator concentrations. Polymers of low polydispersity (Mu [weight-average molecular weight]/Mn [number-average molecular weight] = 1.3-1.6) and with up to 110,000 w re obtained. The... 

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