Light scattering studies on unfractionated poly(<i>n</i>‐docosyl methacrylate)

SynopsisThe specific refractive index increments of 158 natural and synthetic polymers and copolymers in pure and mixed solvents have been collated. Wherever possible the temperature and wavelength (generally 436 and/or 546mp) are quoted.The specific refractive index increment of a solution, dn/dc, is defined as (n -nl)/c, where n , nl, and c are, respectively, the indices of refraction for the solution and solvent and the concentration of solute (in grams per milliliter). In macromolecular chemistry a threefold importance is attached to the increment which, it should be noted, is not a characteristic constant of a given polymer, but depends on the temperature, the wavelength of the light, and the nature of the solvent. Firstly, for example, it affords an indirect means of determining the refractive index of the solute. Accurate values of nz for several proteins have been obtained by Putzeys and Brosteaux,l who measured dn/dc and iiz, the partial specific volume of the protein in essentially aqueous media and applied the LorenzLorentz (L-L) or Gladstone-Dale (G-D) relations.2 For a binary mixture the latter assumes the formSecondly, because of the proportionality between (n -nl) and c, the concentration changes (between solution and solvent or between solutions differing in concentration) across stationary, diffusing or moving boundaries may be followed by observing the corresponding differences in refractive index. The Schlieren optics method incorporates this as its baska Thirdly, and most pertinently to this and the succeeding paper, a precise knowledge of the specific increment presents a prerequisite to the determination of molecular weights by light ~cattering,~ utilizing eq. and the terms have their customary accepted meaning. As the molecular weight M of the polymer is derived from a plot of H C / T against c, an un-3963

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Poly(N‐isopropylacrylamide) Prepared by Free‐Radical Polymerization in Aqueous Solutions and in Nanocomposite Hydrogels

Haraguchi

2011

Macromolecular Symposia

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The molecular characteristics of poly(N‐isopropylacrylamide) (PNIPA) synthesized in aqueous solution were studied with respect to its polymer yield, molecular weight (MW), the polydispersity (the ratio of weight‐ to number‐average molecular weight: Mw/Mn), and intrinsic viscosity ([η]). Gel permeation chromatography (GPC) measurements were performed on unfractionated and fractionated PNIPA by selecting appropriate conditions and solvents, e.g., DMF/10 mM LiBr. It was observed that the MW, Mw/Mn and [η] of PNIPA change significantly depending on the monomer concentration ([NIPA]) in the reaction solution. Linear relationships were observed for the variations of log [NIPA] and Mw/Mn with log Mw. Also, the Mark‐Houwink‐Sakurada equation and the molecular weight exponent α were determined for PNIPA in DMF/10 mM LiBr solution (GPC measurements) and in methanol (light scattering measurements). Also, PNIPA chains were separated from nanocomposite hydrogels with different clay concentrations by decomposing the clay using an aqueous HF solution. The resulting PNIPA showed good correlation between Mw and [η] consistent with that for PNIPA synthesized in aqueous solution. The effects of fractionation and solvents on α and chain conformations, as well as the relationship between α and [η] are discussed.

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Light scattering studies on unfractionated poly(n‐docosyl methacrylate)

Cited by 7 publications

References 9 publications

Specific Refractive Index Increments of Polymers in Dilute Solution

Specific Refractive Index Increments of Polymers in Dilute Solution

Specific refractive index increments of polymer solutions. Part I. Literature values

Poly(N‐isopropylacrylamide) Prepared by Free‐Radical Polymerization in Aqueous Solutions and in Nanocomposite Hydrogels

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