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New hydrogels based on different oligo(alkylene glycol) methacrylate (OAGMA) with inverse thermoresponse and volume phase transition temperature (VPTT) were obtained and characterised in this paper. Synthesis was performed from monomer-solvent (OAGMA-water/ethanol) mixture by simultaneous radiation-induced polymerisation and crosslinking; three different OAGMA (EG(6)MA, EG(6)PG(3)MA, and PG(5)MA) were used. The main focus was made on PEG(6)PG(3)MA hydrogel based on ethylene glycol (EG) propylene glycol (PG) pendant chains with EG (6) and PG (3) block units, since in the case of POPGMA and POEGMA homopolymers (i.e. hydrogels with pure PG and EG pendant chains) the VPTTs were observed far below and far above the human body temperature, respectively. Characterisation of the hydrogels was performed by swelling, UV-Vis, FTIR, SEM, DSC and in vitro biocompatibility (cytocompatibility and haemolytic activity) investigations. Due to the possibility to combine VPTT close to human body temperature with good biocompatibility, new hydrogel based on EGPG block pendant chains showed promising potential for different biomedical applications.

Changes in the structure and dielectric properties of low-density polyethylene were created by gamma irradiation in air, deionised water and nitrogen. Role of irradiation media on dielectric and charge trapping behaviour was studied through dielectric loss and thermally stimulated discharge current measurements. Changes in magnitude, position and activation energy of all dielectric relaxations (gamma, beta and alpha) were found to be dependent on crosslinking and oxidative degradation, two competitive processes which can be tuned by radiation dose and media. Largest changes in the position and activation energy were found for the beta relaxation due to its cooperative nature.

The purpose of this study was to attain oligo(propylene glycol) methacrylate (OPGMA) based hydrogels for different biomedical applications. Since the volume phase transition temperature (VPTT) of poly(oligo(propylene glycol) methacrylate) (POPGMA) homopolymer was below room temperature, it was necessary to tune the thermoresponsiveness and the VPTT to higher temperatures; radical copolymerisation of OPGMA with more hydrophilic and/or pH responsive monomers was used to adjust these values. A series of copolymeric hydrogels with different ratios of OPGMA, 2-hydroxyethyl methacrylate (HEMA) and itaconic acid (IA) was synthesised by gamma radiation. The swelling properties were preliminarily investigated over a wide pH (2.2-9.0) and temperature (4-80 degrees C) ranges. Additional characterization of their structure and properties was conducted by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The presented results revealed temperature/pH dual responsive P(OPGMA/IA) and P(OPGMA/HEMA/IA) copolymers with large diversity in swelling properties, as a result of the addition of OPGMA thermoresponsive units with a lower critical solution temperature (LCST) and IA pH responsive units. It was demonstrated that VPTT can be significantly shifted to higher (e. g. body) temperatures at higher pH values (pH = 4) by increasing the IA content in the hydrogel composition. Due to the possibility of making dual responsive copolymers in the manner explained in this paper, OPGMA based hydrogels show potential for different biomedical applications.