Positron annihilation and diffraction studies of the photopolymers based on the acrylate oligomers

Positron annihilation study of the free volume changes in thermally treated polymers based on acrylate oligomers

“…Larger values of the free volume in D-1 and D-2 with respect to D-5-2 were explained by different sample compositions [10,11]. It seems to be connected with the presence of DMOEM content in composition of the sample, their chains are shorter.…”

“…Therefore, during the fitting for the shortest lifetime, As the o-Ps component is relevant to the free-volume properties, and it is markedly sensitive to the microstructure changes, in this paper, our main attention is paid to the s 3 and I 3 . The lifetime parameters for the samples in the initial state, before thermal treatment, have already been reported [10][11][12]. The variations of o-Ps pick-off lifetime and its intensity for the investigated samples before and after thermal treatment are presented in Table 2.…”

Gamma irradiation effects on UV-cured polymers based on acrylate oligomers studied by positron annihilation lifetime spectroscopy

“…Larger values of the free volume in D-1 and D-2 than D-5-2 were explained from different compositions of samples [10,11]. It seems to be connected with the presence of DMOEM ( Fig.…”

“…If this happens then we have to observe a decrease in V f and s 3 and an increase in I 3 , respectively. On the other hand, it was found in [9][10][11] that intensity is not affected by crosslinking process. Thus degradations seem to be the more likely explanation.…”

Positron annihilation study of the free volume changes in bifocal contact lenses

“…The formation probability and lifetime of the positronium are extremely sensitive to the electron density surrounding Ps. The o-Ps localises in the space between and along the polymer chains and at chain ends (free volume holes), and the lifetime gives an indication on the mean radii of these holes [5][6][7][8]. The original free volume theory for positron annihilation in molecular substances was proposed by Brandt, Berko and Walker [9].…”