Istražene su djelomice interpenetrirane polimerne mreže (DIPM), te smjese na temelju poliesterskih poliuretana (PU) s karboksilnim skupinama i metakrilatnih kopolimera (PM) s tercijarnim amino skupinama, primjenom elektronske spinske rezonancije, ESR-metode spinske probe. Koncentracije funkcionalnih skupina u pretpolimerima iznose od 0 do 0,45 mmol g-1. Na temelju temperaturno ovisnih složenih ESR spektra odre|eni su heterogenost molekulnih gibanja i fazno razdvajanje u ovisnosti o udjelu funkcionalnih skupina. Probe smještene u domenama s većim slobodnim volumenom odgovaraju brzoj komponenti spektra, dok se sporo gibanje pripisuje probama u prostorima manjega slobodnoga volumena, odnosno staklastim domenama. Iz omjera intenziteta brze i spore komponente utvrđeno je da se povečanjem udjela funkcionalnih skupina smanjuje slobodni volumen u mrežama i smjesama. Smanjenje gibljivosti probe u mrežama u odnosu prema smjesama istoga sastava, posljedica je umreživanja polimernih lanaca. Razlike u molekulnom gibanju probe u ovisnosti o raspoloživome slobodnom volumenu povezuju se s difuzijom malih molekula u polimernoj matrici.The electron spin resonance, ESR-spin probe method was applied to study semi-interpenetrating polymer networks, SIPNs and mixtures on the basis of polyester polyurethanes, PU, with carboxylic groups and methacrylic copolymers, PM, with tertiary amine groups. The concentration of functional groups in prepolymers varied from 0 to 0.45 mmol g-1. From the temperature dependent composite ESR spectra motional heterogeneity and phase separation depending on the functional group concentration were deduced. The spin probes embedded within domains with larger free volume or soft domains correspond to the fast motional component, while the slow motion describes spin probes in the regions of smaller free volume characteristic for the glassy polymers. According to the ratio of fast and slow components, free volume decreases with an increase of functional groups concentration in both polymer mixtures and networks. Restriction of spin probe motion or decreased available free volume in polymer networks in comparison with polymer mixtures of the same composition is a consequence of additional crosslinking in the networks. The differences in spin probe motion due to the available free volume are related to the diffusion of small molecules in polymer matrices
