A liquid composition polymerizable by the free-radical polymerization route, with a low shrinkage, to yield organic glasses endowed with high thermal stability, is constituted by the product of transesterification of diallyl-carbonate (A) with a mixture of diol (B) and of a polyol (C) containing from 3 to 6 hydroxy groups in the molecule, or a mixture of a diol (B) with a cycloaliphatic diol (C'), by operating with a molar ratio of A/(B+C) or A/(B+C') equal to, or larger than, 3/1, and with an amount of (C) in the (B+C) mixture equal to, or smaller than, 70% by weight, or with an amount of (C') in the (B+C') mixture equal to, or smaller than, 90% by weight.