Polymer Mixtures - Polymer Science and Engineering - page 238

(b) Solubility parameters of polymers (MPa) 1/2

Polymer b H-bonding group c

δ

Polybutadiene 17.2 Poor

Polyisoprene 17.4 Poor

Poly(butadiene-co-styrene) 75/25 17.4 Poor

Poly(tetramethylene oxide) 17.6 Medium

Poly(butyl methacrylate) 18.0 Poor?

Polystyrene 18.4 Poor

Poly(methyl methacrylate) 19.0 Medium

Poly(butadiene-co-acrylonitrile) 75/25 19.2 Poor

Poly(ethyl acrylate) 19.2 Medium

Poly(vinyl acetate) 19.7 Medium

Poly(vinyl chloride) 19.9 Medium

Poly(methyl acrylate) 20.7 Medium

Polyformaldehyde 20.9 Medium

Ethyl cellulose 21.1 Strong

Poly(vinyl chloride-co-vinyl acetate) 87/13 21.7 Medium

Cellulose diacetate 23.3 Strong

Poly(vinyl alcohol) 26.0 Strong

Polyacrylonitrile 26.0 Poor

Nylon-6,6 28.0 Strong

a Selected data from Ref. [6] .
b Compositions of copolymers are in parts by weight.
c The hydrogen-bonding group of each polymer has been taken as equivalent to that of the parent
monomer. (The hydrogen-bonding tendency can be assigned qualitatively in the order alcohols .
ethers . ketones . aldehydes . esters . hydrocarbons or semiquantitatively from infrared
absorption shifts of CH 3 OD in a reference solvent and in the liquid of interest [7] .)

5.2.2 Flory Huggins Theory

Nonideal thermodynamic behavior has been observed with polymer solutions in
which H m is practically zero. Such deviations must be due to the occurrence of

a nonideal entropy, and the first attempts to calculate the entropy change when
long chain molecules are mixed with small molecules were due to Flory [8] and
Huggins [9] . Modifications and improvements have been made to the original the-
ory, but none of these variations has made enough impact on practical problems
of polymer compatibility to occupy us here.
The Flory

Δ

Huggins model uses a simple lattice representation for the polymer
solution and calculates the total number of ways the lattice can be occupied by
small molecules and by connected polymer segments. Each lattice site accounts
for a solvent molecule or a polymer segment with the same volume as a solvent