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Specific refractive index increments of polymer solutions. Part II. Scope and applications
Author(s) -
Huglin M. B.
Publication year - 1965
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1965.070091220
Subject(s) - refractive index , solvent , polymer , dispersion (optics) , copolymer , monomer , constant (computer programming) , thermodynamics , limiting , volume (thermodynamics) , wavelength , lorentz transformation , chemistry , materials science , analytical chemistry (journal) , physics , optics , organic chemistry , quantum mechanics , mechanical engineering , computer science , programming language , engineering
The data of Part I are examined in the light of accepted theories. The specific refractive index increment ñ of most polymer solutions lies between −0.2 and +0.2 ml./g., although larger values can obtain in circumstances wherein the scattering unit is unusually large, e.g., solutions of partially neutralized polyacids the units of which contain the gegenions. ñ depends on the indices of solvent n 1 and polymer n 2 . Among common solvents, water and 1‐bromonaphthalene are capable of affording high positive and negative values, respectively, for n. The Gladstone‐Dale rule applies rigorously to pure and mixed solvents, but the Lorenz‐Lorentz expression is preferable for evaluating n 2 . Results of current theories applied to mixed solvents and copolymers are summarized. In the former, the true molecular weight M is determined by using ñ and the variation of solvent index with composition. For a copolymer of monomers A and B, M as well as M a and M b are obtainable by using ñ , ñ a , and ñ b . Dispersion is expressed as ( ñ )λ = ( ñ ) 436 [ D ′ + D ″/λ 2 ] at a wavelength λ, and dispersive constants D ′ and D ″ are evaluated for some solutions. ∂ñ/∂ T is generally 3.2 (±2.3) × 10 –4 ml./g./°C. and changes very little with λ. When ñ increases with M, the limiting characteristic value is derived (at 1/ M = 0) from a plot of ñ versus 1/ M . ñ can be determined to a maximum accuracy of 1% by using n 2 calculated from the Lorenz‐Lorentz equation and the experimental partial specific volume.