Abstract
The solubility of iodine in PDS (polydimethylsiloxane) has been measured for varying degrees of polymerization (number of silicon atoms) from 2 to 470. The data obtained show good agreement with a solubility equation derived on the basis of the following two assumptions : (1) a PDS molecule is composed of several completely freely oriented segments, and (2) the mixture of these segments and iodine can be treated as a regular solution as far as enthalpy calculation is concerned.
A constant segment solubility parameter δS, which is about 7.5 cal1/2/cm3/2, is obtained regardless of degree of polymerization by the use of this solubility equation. This value is nearly the same as that of silicon rubber from swelling data. On the basis of the discussions above, it is concluded that the size of a segment is nearly equal to that of a siloxane unit. The molecular-attraction constant for a siloxane unit is found to be 580-600 cal1/2•cm3/2/mol.
