[en] The relationship between the detection sensitivity for charged particles and the molecular structure of polymers like CR-39 was studied while changing the average chain length of the carbonate linkages cross-linking the polyallyl chains. It has been found that the polymer shows the highest sensitivity when the length of the carbonate linkages is about 1.6 times longer than that of CR-39. Just after polymerization this polymeric track detector named SR-90 has about 3 times higher sensitivity than CR-39 but ageing effects on its sensitivity are very strong. In this connection a model of the latent track formation and the mechanism of the track fading are discussed on the basis of the recombination of free radicals produced by charged particles. (author)