The effect of crosslinking on the glass transition temperature and the specific volume of poly(diethylene glycol bis(allyl carbonate)) networks was studied using a series of networks with progressively decreasing density of crosslinks. The networks were prepared by a bulk copolymerisation of ethylene glycol bis(allyl carbonate) with an increasing amount of allyl ethoxyethyl carbonate. It was found that their glass transition temperature determined by the Dynamic Mechanical Thermal Analysis decreases linearly with increasing concentration of the monoallyl comonomer whilst the increase in their specific volume is non-linear. This is explained by the non-equilibrium state of the networks at the temperature of the specific volume measurement.