Changes in structure of PA6 during processing

Using thermomechanical analysis, the molecular weight distribution and relaxation transitions were investigated in commercial PA6 and in this polymer after passage through an extruder with a static mixer. A diblock or triblock amorphous structure and a crystalline portion in the studied PA6 were found. These amorphous structures differ in the glass transition temperatures by 80–180°C. There was a principal difference in the topological and molecular structures of PA6 depending on the processing conditions—number of cycles and shear rates. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2361–2368, 2001     

Reducing life‐cycle environmental impacts of coal‐power by using coal‐mine methane

The exploitation of coal‐mine methane is analysed to reduce the environmental impact from coal power systems. The analyses are based on a life cycle assessment, and the results were compared with carbon‐capture and storage technologies. The results suggest that by increasing the use of coalmine methane, the environmental impacts of coal power plants could be clearly reduced. Although the CO₂ reduction is much less than through sequestration of CO₂, increased use of coal‐mine methane in Poland could potentially reduce greenhouse gas emissions up to 9 million tonnes of CO₂ per year, which corresponds to about 2.5% of the emissions of Poland. Copyright © 2012 John Wiley & Sons, Ltd.     

The effect of post-mortem ageing and heating on water retention in bovine muscles

The muscles semitendinosus (ST) and psoas major (PM) were removed from chilled young bull carcasses 24 h after slaughter and stored at 4 °C. At the 1st, 6th and 12th day of post-mortem ageing the chemical composition (moisture, fat, protein, collagen) and contents of free, immobilized and unfreezable water in the muscles were estimated. The muscle steaks were boiled at 100 °C, roasted at 170 °C or fried at 160 °C to an internal temperature of 75 °C, and the amounts of total, free, immobilized, and unfreezable water in heated muscles were evaluated. The unfreezable water was estimated by DSC. In the raw muscles immobilized water constituted 74–75%, free water 16.6–17.6% and unfreezable water 7–8% of the total water. Independent of time of ageing, PM muscle contained significantly more free water than ST muscle. During post-mortem ageing, changes in free, immobilized and unfreezable water in muscles were not significant. The level of free water was highest in boiled and least in fried meat, however the amount of immobilized water was highest in fried and lowest in boiled meat. The amount of unfreezable water in muscles heated after 12 days of post-mortem ageing decreased.     

The use of long-chain plant polyprenols as a means to modify the biological properties of new biodegradable polyurethane scaffolds for tissue engineering. A pilot study

Microporous membranes for tissue engineering were produced from new biodegradable polyurethane based on hexamethylene diisocyanate, poly(ε-caprolactone) diol and 1,4:3,6-dianhydro-d-sorbitol. The interconnected pores had an average size in the range of 5–100 μm. The tensile strength at break, the Young’s modulus and elongation at break of the membranes were 3.2 ± 0.3 MPa, 25.2 ± 1.5 MPa and 190 ± 12%, respectively, while nonporous foils from the same polymers had a tensile strength at break of 40 ± 2 MPa, a Young’s modulus of 91 ± 6 MPa, and an elongation at break of 370 ± 10%. The membranes were incubated for 10 days in a 2.65 vol% solution of long-chain plant polyprenol in n-hexane to promote their interaction with cells and tissues. The polyprenol was isolated from leaves of Magnolia cobus and was a mixture of prenol-10 and prenol-11. The prenol-impregnated membranes and nonimpregnated membranes (control) were tested in cell culture to assess whether impregnation has a beneficial effect on cell-material interaction. The cells used in the test were chondrocytes isolated from the articular-epiphyseal cartilage of leg bones of 5-day-old inbred LEW rats. The time of culture was 2 and 5 weeks. Both, the nonimpregnated and impregnated polyurethane membranes supported attachment and growth of rat chondrocytes. The cells firmly attached to the surface of the microporous membranes, invaded the pores and maintained the round shape characteristic for chondrocyte-like-morphology. Abundant fibrillar extracellular matrix produced by the cells resembled the network formed by chondrocytes in vivo. The cells produced relatively more extracellular matrix in the membranes impregnated with polyprenol than in the control membranes. Impregnation of polyurethane scaffolds with biologically active amphiphilic polyprenols may be a route to facilitate the cell–material interaction.     

Synthesis of linear polysiloxanes with electron-donating organophosphorus pendant groups by kinetically controlled ring-opening polymerization

Six-membered ring siloxane monomers containing a phosphorus electron-donating groupR=–CH₂CH₂PPh₂ (1), –CH₂CH₂P(S)Ph₂ (2), and –CH₂CH₂P(O)Ph₂ (3) were synthesized. The anionic ring-opening polymerization of these monomers with kinetic control of products has been studied using tetrahydrofuran (THF) as solvent and lithium silanolates as initiators. The polymerization leads to a high molecular weight linear polymer with a very good yield in the case of2 and with a fairly good yield in the case of1 and3. The presence of the phosphorus group enhances the cyclization and broadens the molecular weight distribution of the linear polymer. This effect is relatively weak for the thiophosphinoyl group. At least in the case of the polymer obtained from2, phosphorus groups are distributed uniformly in the macromolecule, however, their arrangement along the chain is not regular. The interaction of polymers obtained from monomers1, 2, and3 with some electrophiles such as alkyl or silyl halides was demonstrated to lead to generation of polyelectrolytes.     

Thioether–Polyglycidol as Multivalent and Multifunctional Coating System for Gold Nanoparticles

Thiofunctional polymers are the established standard for the coating and biofunctionalization of gold nanoparticles (AuNPs). However, the nucleophilic and oxidative character of thiols provokes polymeric crosslinking and significantly limits the chemical possibilities to introduce biological functions. Thioethers represent a chemically more stable potential alternative to thiols that would offer easier functionalization, yet a few studies in the literature report inconclusive data regarding the efficacy of thioethers to stabilize AuNPs in comparison to thiols. A systematic comparison is presented of mono‐ versus multivalent thiol‐ and thioether‐functional polymers, poly(ethylene glycol) versus side chain functional poly(glycidol) (PG) and it is shown that coating of AuNPs with multivalent thioether‐functional PG leads to superior colloidal stability, even under physiological conditions and after freeze‐drying and resuspension, as compared to thiol analogs at comparable polymer surface coverages. In addition, it is shown that a wide range of functional groups can be introduced in these polymers. Using diazirine functionalization as example, it is demonstrated that proteins can be covalently immobilized, and that conjugation of antibodies via this strategy enables efficient targeting and laser‐irradiation induced killing of cells.     

Properties of anionic polymerized ε‐caprolactam in the presence of carbon nanotubes

The results of the investigations of the relations between structure, physical and usage properties of polyamide 6 (PA6) reinforced with multiwall carbon nanotubes (MWNTs) are presented. A method of in situ anionic bulk polymerization of ε‐caprolactam in the presence of MWNTs was used for the preparation of reinforced PA6. The polymerization product was crushed, and the pellets of PA6 and PA6/MWNTs composites were injection molded to produce the standard test specimens for various measurements. The surface morphology (SEM), thermal (DSC, TGA, DMTA), and mechanical properties (tensile strength, Charpy's notched impact strength) of these materials were examined. Some differences between our specimens and those obtained by hydrolytic polymerization of ε‐caprolactam (CL) were found. It was found that a small amount of carbon nanotube decreases the crystallinity degree of PA6 matrix in the composites. The thermal stability was higher than that for neat PA6. DMTA results showed that the magnitudes of the storage modulus are higher for the PA6/MWNTs composites than for the unmodified PA6 in the temperature range between ?90 and 200°C. The tensile strength and tensile modulus are higher compared with the neat PA6. The elongation at break showed no noticeable change in the range of MWNTs loading considered, while the Charpy's notched impact strength slightly decreased. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Reactive polymeric microspheres: Catalytic reduction of a nitrobenzene derivative

Polymeric microspheres have been demonstrated as a potentially useful vehicle for targeted delivery applications. In this work we report on the preparation of polymer microspheres capable of performing specific reaction chemistry. The microspheres are modified with silver nanoparticles in a two‐step reaction. The first step involves formation of the microsphere by UV‐induced polymerization of pyrrole and the second step is the reduction of silver cations to metallic silver in situ. The resulting Ag‐decorated microspheres were characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, energy dispersive X‐ray, and thermogravimetry analysis. The catalytic reaction behavior of the decorated microspheres was illustrated through the reduction reaction of m‐nitrobenzene sulfonate acid in the presence of sodium borohydride. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43653.     

High-Resolution scanning electron micrographs of freeze-cracked cells in testes from normal and irradiated rats at different stages of gonadal development

Newly developed techniques in high-resolution scanning electron microscopy (SEM) and for tissue-processing procedures have been applied to an investigation of structures of various cells in rat testes at different stages of gonadal maturation. A series of high-resolution SEM micrographs are presented which survey the surfaces of different types of testis cells during normal development, and which also illustrate ultrastructural features of some of their intracellular organelles. In addition, a series of high-resolution SEM micrographs are presented which compare the structural features of Sertoli cells in normal testes with those in germ-cell-depleted testes obtained from rats killed at varying times after having been irradiated in utero. We describe our observations on the structural properties of surfaces and intracellular organelles in Sertoli cells, Leydig cells, peritubular myoid cells, and some classes of germinal cells. We also consider the possible role of Sertoli cell apical cytoplasmic processes in lumen formation. Similarities are pointed out between the structure of germ-cell-depleted testes, resulting from irradiation in utero, and the structure of germ-cell-depleted testes in seasonal breeders during periods of involution. Finally, we discuss advantages and disadvantages of methods employed to reveal the fine structure of intracellular organelles in cells of the testis.     

Weathering of low‐density polyethylene grafted with itaconic acid in laboratory tests

Polyethylene grafted with itaconic acid was subjected to weathering under laboratory accelerated conditions. The course of the photo‐oxidative degradation process of that material was studied by FTIR spectroscopy both through quantitative measurements of changes in absorbance values at selected wave numbers and through measurements of surface area values for absorption bands which were separated by means of deconvolution. The use of both those procedures of quantitative determinations resulted in a general conclusion that the oxidation process was initiated from the very first moment of irradiation, and it produced ketones, acids, esters (intramolecular and of acetate type), peracids, peresters, hydroperoxides, and alcohols. The molecular weight values and gel number values, which were established as well, pointed out that oxidation was accompanied by cracking of polymer macromolecules, and also by polymer crosslinking to a limited degree. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012