polyethylene glycol MW 300

wt%     	log P (dynes/cm^2)

2.6		6.36
5.0		6.73
10.0		7.00
15.0		7.23
20.0		7.41
25.0		7.57
30.0		7.71

An equation that fits this data is the following.

log P = a + b * (wt%) ^ c

where a = 4.79, b = 1.28 and c = 0.24

Note that it should be applied only over the range of pressures measured.