Stefan Połowiński

Modification of polysiloxanes by free-radical addition of pyridylthiols to the vinyl groups of the polymer

Abstract Polysiloxanes containing pyridyl groups were prepared by thiol-ene addition to vinyl side groups of polysiloxanes. Apart from polymethylvinylsiloxane, poly(methylvinylsiloxane-co-dimethylsiloxane)s synthesized by three different methods were used: (1) equilibrium copolymerization of 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane (V4) with hexamethylcyclotrisiloxane (D3); (2) kinetically controlled homopolymerization of 1-vinyl-1,3,3,5,5-pentamethylcyclotrisiloxane; and (3) kinetically controlled copolymerization of V4 and D3, which permitted us to obtain siloxane copolymers with different arrangements of the pyridyl groups along the chain. Addition of 2-(4-pyridyl)ethanethiol (PET) to the vinyl groups of these polymers proceeded with high yields, leading preferentially to β-addition products. The addition of 4-pyridylthiol (PT) proceeded much less readily. Polymers were characterized by FT-IR, 1H and 13C NMR, and by thermal analytical methods.

Synthesis of microsequential methylvinylsiloxane–dimethylsiloxane copolymers by nonequilibrium copolymerization

Nonequilibrium anionic ring-opening copolymerization of 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane (V4) with hexamethylcyclotrisiloxane (D3) was examined as a route to methylvinyl–dimethylsiloxane microsequential copolymers. The copolymerization was carried out in toluene and was initiated with Me3SiCH2Li using DMSO as the promoter. Distribution of siloxane units obtained from kinetic analysis based on first-order Markovian statistics was compared with that found from analysis by 29Si NMR spectroscopy. Results showed that although chain transfer and back-biting play some role in this system, the kinetics of copolymerization may be described to a reasonable approximation by the first-order Markov model.

Antibacterial properties of polypropylene textiles modified by poly(2-(N,N-dimethyloamino ethyl) methacrylate)

Polypropylene nonwoven fabrics samples were modified using poly(2-(N,N-dimethyloamino ethyl) methacrylate) (PDAMA) and silver-containing layers. The structure of the material after modification was confirmed using scanning electron mocroscope, energy-dispersive X-ray spectroscopy, Fourier Transfer Infrared Spectroscopy (FTIR), and electro-kinetic measurements. It was found that samples with external PDAMA layers have excellent activity against Staphylococcus aureus under dynamic contact conditions. In contrast, samples finished with deposited silver showed little antimicrobial effect. Antibacterial tests conducted under static conditions showed no antibacterial activity irrespective of the deposited layers.

PLA nonwovens modified with poly(dimethylaminoethyl methacrylate) as antimicrobial filter materials for workplaces

The objective of the present study was to assess the antimicrobial effectiveness of silver- and copper-modified polylactide (PLA)–poly(dimethylaminoethyl methacrylate) (PDMAEMA) nonwovens used as materials for the production of air purifying respirators. The antimicrobial activity of six types of PLA nonwovens, with different PDMAEMA, Ag, and Cu contents, were tested using the ATCC 100 method. Microorganisms were isolated from the air in 12 workplaces within composting plants, tanneries, and museums. Dominant bacterial and fungal species were identified using 16S RNA and ITS1/2 molecular analysis, respectively. Air samples collected from the composting plant and tannery were highly contaminated with bacteria, while those from museums with fungi (103–104 CFU/m3). We identified potentially pathogenic microorganisms from the following genera: Bacillus, Corynebacterium, Pseudomonas, Candida, Aspergillus, Penicillium, Scopulariopsis, and Paecilomyces. PLA nonwovens containing 5.1% poly(dimethylaminoethyl methacrylate) and 2.7% Ag or 3.8% Cu exhibited good antimicrobial properties (R > 99.9%) against the pathogenic strains found in the above workplaces. These nonwovens also have good inspiratory resistance parameters.