Synergistic Self-Healing Enhancement in Multifunctional Silicone Elastomers and Their Application in Smart Materials.

Organosilicon polymers (silicones) are of enduring interest both as an established branch of polymer chemistry and as a segment of commercial products. Their unique properties were exploited in a wide range of everyday applications. However, current silicone trends in chemistry and materials engineering are focused on new smart applications, including stretchable electronics, wearable stress sensors, protective coatings, and soft robotics. Such applications require a fresh approach to methods for increasing the durability and mechanical strength of polysiloxanes, including crosslinked systems. The introduction of self-healing options to silicones has been recognized as a promising alternative in this field, but only carefully designed multifunctional systems operating with several different self-healing mechanisms can truly address the demands placed on such valuable materials. In this review, we summarized the progress of research efforts dedicated to the synthesis and applications of self-healing hybrid materials through multi-component systems that enable the design of functional silicon-based polymers for smart applications.

Eugenol-Based Polymeric Materials-Antibacterial Activity and Applications.

Eugenol (4-Allyl-2-methoxy phenol) (EUG) is a plant-derived allyl chain-substituted guaiacol, widely known for its antimicrobial and anesthetic properties, as well as the ability to scavenge reactive oxygen species. It is typically used as a mixture with zinc oxide (ZOE) for the preparation of restorative tooth fillings and treatment of root canal infections. However, the high volatility of this insoluble-in-water component of natural essential oils can be an obstacle to its wider application. Moreover, molecular eugenol can be allergenic and even toxic if taken orally in high doses for long periods of time. Therefore, a growing interest in eugenol loading in polymeric materials (including the encapsulation of molecular eugenol and polymerization of EUG-derived monomers) has been noted recently. Such active macromolecular systems enhance the stability of eugenol action and potentially provide prolonged contact with pathogens without the undesired side effects of free EUG. In this review, we present an overview of methods leading to the formation of macromolecular derivatives of eugenol as well as the latest developments and further perspectives in their pharmacological and antimicrobial applications.

Self-Healing Antimicrobial Silicones-Mechanisms and Applications.

Organosilicon polymers (silicones) are an important part of material chemistry and a well-established commercial product segment with a wide range of applications. Silicones are of enduring interest due to their unique properties and utility. Recently, new application areas for silicone-based materials have emerged, such as stretchable electronics, wearable stress sensors, smart coatings, and soft robotics. For this reason, research interest over the past decade has been directed towards new methods of crosslinking and increasing the mechanical strength of polyorganosiloxanes. The introduction of self-healing mechanisms may be a promising alternative for such high-value materials. This approach has gained both growing research interest and a rapidly expanding range of applications. Inherent extrinsic and intrinsic self-healing methods have been used in the self-healing of silicones and have resulted in significant advances in polymer composites and coatings, including multicomponent systems. In this review, we present a summary of research work dedicated to the synthesis and applications of self-healing hybrid materials containing polysiloxane segments, with a focus on antimicrobial and antifouling coatings.

Hybrid Perovskite-Based Materials Modified with Polyhedral Silsesquioxanes-Structure and Properties.

Polyhedral oligomeric silsesquioxanes (POSS) and hybrid organo-halide perovskites are two important types of hybrid nanoscale frameworks with great potential in materials chemistry. Both are currently under intensive investigation for a wide range of possible applications. Recent results suggest that POSS can be attractive passivating and structure-controlling agents for perovskite materials. In this review, we present the importance of POSS in engineering the structures of inorganic cesium-halide perovskites CsPbX3 (X = Cl, Br, I) to create a new class of hybrid derivatives with improved properties. The combination of these two components can be an effective strategy for controlling the perovskite crystallization process. In addition, passivation of surface defects/bulk and the engineering of energy and optoelectronic properties of perovskite-based materials can be achieved following this method. In this minireview, we summarized the existing literature reports on the structural specificity and properties of hybrid POSS perovskites.

Hybrid Bio-Based Silicone Coatings with Anti-adhesive Properties.

Hybrid polysiloxanes and polysilsesquioxanes grafted with naturally occurring bioactive phytochemicals: eugenol and linalool, were synthesized and investigated with regard to their structure and properties. The two series of materials, differing in the type of inorganic structure and the content of active groups, were coated onto the surface of glass plates, and their antibiofilm activities against bacteria Aeromonas hydrophila were assessed by luminometry and fluorescence microscopy. Bioactivity was correlated with specific properties of the hybrid coatings (chemical structure, surface free energy and adhesiveness). The functionalized polysilsesquioxanes exhibited the most favorable anti-adhesive effects. Cell adhesion after 6 days of incubation, expressed as RLU/cm2, was significantly reduced (44 and 67 for, respectively, Z-E-100 and Z-L-100, compared to 517 for the control glass carrier). The surface stickiness of polysiloxane films deteriorated their anti-adhesion properties, despite the presence of a large amount of bioactive species.

Trends in Adolescent Substance Use: Analysis of HBSC Data for Four Eastern European Countries, 1994-2018.

The aim of the study was to analyze the trends of adolescent substance use in four eastern European countries over the time period from 1994 to 2018. The four countries in focus were selected based on their shared historical backgrounds and major economic and social transformations experienced. METHODS: Two decades (1993/1994-2017/2018) of repeated cross-sectional data from the Estonian, Latvian, Lithuanian, and Polish Health Behaviour in School-aged Children survey were used. Data comprised 42,169 school children 15 years of age (9th grade). The following categories of substance use were included: regular alcohol consumption and drunkenness, tobacco smoking, electronic cigarette smoking, and cannabis use. Trends in substance use over time were tested using Jonckheere's trend test. RESULTS: Prevalence of substance use among adolescents over time revealed that the Baltic states and Poland have faced relatively different temporal trends. In the Baltic states, there was a general increase during the period of 1994-2002, which was followed by a period of peaking or stability between 2002-2010, and then decreasing trends of these risky behaviors from 2010 onwards. In Poland, the same period had less consistent patterns, with decreasing trends starting much earlier on. The prevalence of cannabis use, which had been measured since 2006, had its own unique pattern with many fluctuations within and between countries. CONCLUSIONS: The findings on the prevalence of substance use among adolescents from 1994 to 2018 revealed that the Baltic states and Poland have faced relatively different temporal trends. These countries might be facing new public health challenges in a near future, e.g., use of electronic cigarettes and cannabis use among adolescents.

Who Is Able to Resist What Is Forbidden?-The Relationship between Health Literacy and Risk Behaviours in Secondary School Students in the Broader Social and Educational Context.

In the last Health Behaviour in School-Aged Children (HBSC) survey conducted in Poland in 2018, a group of 17-year-old adolescents (n = 1663; mean age 17.63 ± 0.36 years) was included outside the international protocol. This allowed an assessment to be made of their level of health literacy (HL) using the 10-point HBSC research tool. The aim of the study was to investigate the relationship between HL and risk behaviours (RB). A standardised index of RB in the last 30 days was considered as an outcome measure. This index was significantly higher in the group with low HL (0.318 ± 1.269) in comparison with the group with high HL (-0.083 ± 0.962). In a multivariate linear regression model, the strongest predictors of RB were gender, academic performance and level of regional deprivation, but the association with HL remained significant. This significant association persisted in general schools and in girls but disappeared in vocational schools and in boys. It was also shown that in rural areas, good academic performance has a less significant impact on RB if the HL level is low. The analyses led to the conclusion that when examining the relationship between HL and RB in older adolescents, it is advisable to take into account gender, the educational track and neighbourhood characteristics.

Self-Healing Silsesquioxane-Based Materials.

This review is devoted to self-healing materials (SHM) containing polyhedral oligomeric silsesquioxanes (POSS) as building blocks. The synthetic approach can vary depending on the role POSS are expected to play in a given system. POSS (especially double-decker silsesquioxanes) can be grafted in side chains of a polymer backbone or used as segments of the main chain. Appropriate functionalization allows the formation of dynamic bonds with POSS molecules and makes them an active component of SHM, both as crosslinking agents and as factors that enhance the dynamics of macromolecules in the polymer matrix. The latter effect can be achieved by reversible release of bulky POSS cages or by the formation of separated inclusions in the polymer matrix through hydrophobic interactions and POSS aggregation. The unique properties of POSS-based self-healing systems make them interesting and versatile materials for various applications (e.g., repairable coatings, sealants, sensors, soft materials for tissue engineering, drug delivery, and wound healing).

Modification of Polylactide Nonwovens with Carbon Nanotubes and Ladder Poly(silsesquioxane).

Electrospun nonwovens of poly(L-lactide) (PLLA) modified with multiwall carbon nanotubes (MWCNT) and linear ladder-like poly(silsesquioxane) with methoxycarbonyl side groups (LPSQ-COOMe) were obtained. MWCNT and LPSQ-COOMe were added to the polymer solution before the electrospinning. In addition, nonwovens of PLLA grafted to modified MWCNT were electrospun. All modified nonwovens exhibited higher tensile strength than the neat PLA nonwoven. The addition of 10 wt.% of LPSQ-COOMe and 0.1 wt.% of MWCNT to PLLA increased the tensile strength of the nonwovens 2.4 times, improving also the elongation at the maximum stress.

Phase Structure and Properties of Ternary Polylactide/Poly(methyl methacrylate)/Polysilsesquioxane Blends.

Ternary blends of polylactide (PLA, 90 wt.%) and poly(methyl methacrylate) (PMMA, 10 wt.%) with functionalized polysilsesquioxanes (LPSQ-R) were obtained by solution blending. R groups in LPSQ containing hydroxyethyl (LPSQ-OH), methylglycolic (LPSQ-COOMe) and pentafluorophenyl (LPSQ-F5) moieties of different chemical properties were designed to modify PLA blends with PMMA. The effect of the type of LPSQ-R and their content, 1-3 wt.%, on the structure of the blends was studied with scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (SEM-EDS), dynamic mechanical thermal analysis (DMTA) and Raman spectroscopy. Differential scanning calorimetry (DSC) and tensile tests also showed various effects of LPSQ-R on the thermal and mechanical properties of the blends. Depth-sensing indentation was used to resolve spatially the micro- and nano-scale mechanical properties (hardness and elastic behaviour) of the blends. The results showed clearly that LPSQ-R modulate the structure and properties of the blends.

New Antiadhesive Hydrophobic Polysiloxanes.

Intrinsic hydrophobicity is the reason for efficient bacterial settlement and biofilm growth on silicone materials. Those unwelcomed phenomena may play an important role in pathogen transmission. We have proposed an approach towards the development of new anti-biofilm strategies that resulted in novel antimicrobial hydrophobic silicones. Those functionalized polysiloxanes grafted with side 2-(carboxymethylthioethyl)-, 2-(n-propylamidomethylthioethyl)- and 2-(mercaptoethylamidomethylthioethyl)- groups showed a wide range of antimicrobial properties towards selected strains of bacteria (reference strains Staphylococcus aureus, Escherichia coli and water-borne isolates Agrobacterium tumefaciens, Aeromonas hydrophila), fungi (Aureobasidium pullulans) and algae (Chlorella vulgaris), which makes them valuable antibacterial and antibiofilm agents. Tested microorganisms showed various levels of biofilm formation, but particularly effective antibiofilm activity was demonstrated for bacterial isolate A. hydrophila with high adhesion abilities. In the case of modified surfaces, the relative coefficient of adhesion for this strain was 18 times lower in comparison to the control glass sample.

Hybrid Fluorescent Poly(silsesquioxanes) with Amide- and Triazole-Containing Side Groups for Light Harvesting and Cation Sensing.

Hybrid polymers containing pyrene (Py) units bound to linear poly(silsesquioxane) (LPSQ) chains through flexible linkers containing heteroatoms (S, N, O) (LPSQ-triazole-Py and LPSQ-amide-Py) exhibit intense fluorescence emission, both in very diluted solutions (c = 10-8 mol/L) and in the solid state. The materials are thermally stable and exhibit good thin film forming abilities. Their optical and physicochemical properties were found to be strongly dependent on the structure of the side chains. Comparative studies with octahedral silsesquioxane (POSS) analogues (POSS-triazole-Py and POSS-amide-Py) emphasized the role of the specific double-strand architecture of the LPSQ backbone and distribution of side Py groups for their photo-luminescent properties. The new hybrid materials were tested as fluorescence energy donors to red-emitting dyes (Nile Red and Coumarine 6). All the silsesquioxanes studied were found to be able to transfer FL emission energy to Coumarin 6, irrespectively of their spatial structure. However, due to the differences in the wavelength range of FL emission, only LPSQ-triazole-Py were able to act as energy donors to Nile Red. The Py-grafted LPSQ may be also applied for development of soluble and highly emissive chemosensors. Their fluorescent nature was explored for the detection of Cu(II), Fe(III), Co(II), Ag(I), Hg(II), Mg(II), Ca(II), Pb(II) and Zn(II). The morphology of the side chains and hydrogen-bonding interactions influenced the sensing capacity of all the studied materials.

Psychosocial determinants of sexual norms and their impact on sexual debut in Polish adolescents.

OBJECTIVES: In an attempt to describe composite scales relating to sexual norms, we present their structure, psychosocial determinants, and the association with adolescent sexual initiation. METHODS: A representative sample of Polish students was surveyed in 2015 (n = 1024, mean age 17.8 ± 0.31). Three scales of sexual norms were identified using principal component analysis. Logistic regression and path models were applied. RESULTS: The scales concerning stereotype gender norms, as well as restrictive and permissive sexual norms, were developed. Restrictive norms lead to later sexual initiation and were more frequent in combination with love for the first partner. The variability of all the indices was significantly correlated with the peer environment. A number of direct and indirect paths were found among the above indices, family relationships (support, communication), and socio-emotional strengths, such as the meaning of life, coherence, and self-esteem. CONCLUSIONS: The norms of sexual morality should be included in the analysis of the determinants of adolescent sexual behaviours along with an investigation of complex causal models. The results may contribute to improvement in sexual health promotion.

Supramolecular Interactions in Hybrid Polylactide Blends-The Structures, Mechanisms and Properties.

The conformation of polylactide (PLA) chains can be adjusted by supramolecular interactions (the formation of hydrogen bonds or host-guest complexes) with appropriate organic molecules. The structures formed due to those intermolecular interactions may act as crystal nuclei in the PLA matrix ("soft templating"). In this review, the properties of several supramolecular nucleating systems based on synthetic organic nucleators (arylamides, hydrazides, and 1,3:2,4-dibenzylidene-d-sorbitol) are compared to those achieved with biobased nucleating agents (orotic acid, humic acids, fulvic acids, nanocellulose, and cyclodextrins) that can also improve the mechanical properties of PLA. The PLA nanocomposites containing both types of nucleating agents/additives are discussed and evaluated in the context of their biomedical applicability.

Antimicrobial and Antibiofilm N-acetyl-L-cysteine Grafted Siloxane Polymers with Potential for Use in Water Systems.

Antibiofilm strategies may be based on the prevention of initial bacterial adhesion, the inhibition of biofilm maturation or biofilm eradication. N-acetyl-L-cysteine (NAC), widely used in medical treatments, offers an interesting approach to biofilm destruction. However, many Eubacteria strains are able to enzymatically decompose the NAC molecule. This is the first report on the action of two hybrid materials, NAC-Si-1 and NAC-Si-2, against bacteria isolated from a water environment: Agrobacterium tumefaciens, Aeromonas hydrophila, Citrobacter freundii, Enterobacter soli, Janthinobacterium lividum and Stenotrophomonas maltophilia. The NAC was grafted onto functional siloxane polymers to reduce its availability to bacterial enzymes. The results confirm the bioactivity of NAC. However, the final effect of its action was environment- and strain-dependent. Moreover, all the tested bacterial strains showed the ability to degrade NAC by various metabolic routes. The NAC polymers were less effective bacterial inhibitors than NAC, but more effective at eradicating mature bacterial biofilms.

Poly(silsesquioxanes) and poly(siloxanes) grafted with N-acetylcysteine for eradicating mature bacterial biofilms in water environment.

Bacteria adapt to their living environment forming organised biofilms. The survival strategy makes them more resistant to disinfectants, which results in acute biofilm-caused infections, secondary water pollution by biofilm metabolites and bio-corrosion. New, efficient and environmentally friendly strategies must be developed to solve this problem. Water soluble N-acetyl derivative of L-cysteine (NAC) is a non-toxic compound of mucolytic and bacteriostatic properties that can interfere with the formation of biofilms. However, it can also be a source of C and N for undesired microorganisms, as well as a reason for some adverse human health effects. Consequently, novel procedures are required, that would decrease the take-up of NAC but not reduce its antibacterial properties. We have grafted N-acetyl-l-cysteine onto linear poly(vinylsilsesquioxanes) and poly(methylvinylsiloxanes) via thiol-ene addition. Antibacterial activity of the obtained hybrid materials (respectively, NAC-Si-1 and NAC-Si-2) was determined against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus strains. Native NAC inhibited growth of planktonic cells for the tested bacteria at concentration 0.25% w/v. Inhibition with equivalent solutions of the polymer derivatives was less effective due to the lack of SH groups. However, the tested polymers proved to be quite effective in eradication of mature biofilms. Treatment with 1% w/v emulsions of the hybrid polymers resulted in a significant reduction of viable cells in biofilm matrix despite the absence of thiol moieties. The effect was most pronounced for mature biofilms of S. aureus eradicated with NAC-Si-2.

Current trends in tobacco smoking among 15-year-old adolescents in Poland in the background of 30 countries.

The international HBSC (Health Behaviour in School-aged Children) survey has enabled the comparison of the patterns of changes with respect to a number of health indicators in adolescence. The aim of the study was to show international trends and how the position of Poland in international rankings of smoking prevalence has changed since 2002. Material and Methods: The study comprised 30 countries for which data was available from four rounds of HBSC survey (2002-2014). In total, 218 759 15-year-olds were surveyed, including 7289 in Poland. For each country a linear trend was estimated, separately for boys and girls, to describe changes in regular smoking (daily or at least once a week). Results: In the investigated period, the percentage of 15-year-old boys who smoke every week fell in Poland from 26.2% to 15.5%, and the respective percentage in girls decreased from 17.2% to 14.7%. This means annual decrease of 0.88% in boys and 0.24% in girls. In a combined international sample, exactly the same as in Poland rate of change was noted in boys; however, a definitely faster in girls (0.95% a year). The highest rate of change was observed in Ukraine, Germany and Norway, while the lowest in Greece, Croatia and Israel. Poland's position in the international ranking moved from 8th to 24th, providing that the countries are listed according to the growing percentage of 15-year-olds of both genders who smoke regularly. Conclusions: Decrease in the prevalence of smoking among Polish adolescents, observed from the beginning of this century, has been undoubtedly a success related to the implemented preventive measures. However, attention should be drawn to the strategies launched in countries which achieved better results than Poland, as well as to the reasons of less positive trends among Polish girls.

[School performance as a mediator of the association between family affluence and risk behaviour in adolescents in Poland].

It can be assumed that family socioeconomic status does affect the frequency of undertaking risk behaviours by adolescents directly or indirectly, i.e. by having impact on other proven risk factors. The objective of the study was to show the combined influence of family affluence and school performance on alcohol consumption and tobacco and marijuana smoking, defined as risk behaviour syndrome. Material and Methods: The survey was conducted on a nationwide sample of 1,202 adolescents aged on average 15.6 years (SD=0.31), who participated in the HBSC (Health Behaviour in School-aged Children) survey. Structural equation models were used in the analysis in order to test the hypothesis that school performance is a mediator of the association between family affluence and risk behaviour. Results: It was found that 23.0% of adolescents smoked tobacco; 40.8% drank alcohol; 10.2% smoked marijuana. One fifth of the respondents used one of those substances frequently, i.e. more than 5 days in the last month. It was shown that family affluence is strongly correlated with school performance (p<0.001), however, there was no direct relationship with the general level of psychoactive substance use (p=0.481). In analysing individual substances, only with regard to marijuana it was found that it was used less frequently in more affluent families. School performance resulted to be a stronger mediator of the relationship between family affluence and risk behaviour in girls (Sobel's test: p=0.013) than in boys (p=0.111). In the analysis of the social determinants of the health behaviour of adolescents, indirect correlations and confounding variables should be considered. Worse school performance may be the cause or effect of a more frequent psychoactive substance.

Supramolecular self-assembly of linear oligosilsesquioxanes on mica--AFM surface imaging and hydrophilicity studies.

Linear oligomeric [2-(carboxymethylthio)ethylsilsesquioxanes] (LPSQ-COOH) adsorb spontaneously on muscovite mica and form smooth, well-ordered lamellar structures at the liquid-solid interface. Side carboxylic groups, having donor-acceptor character with regard to hydrogen bonds, are engaged both in multipoint molecule-to-substrate interactions and intermolecular cross-linking. The unique arrangement of silsesquioxane macromolecules, with COOH groups situated at the interface with air, produces highly hydrophilic surfaces of good thermal and solvolytic stability. Supramolecular assemblies of LPSQ-COOH were studied using atomic force microscopy (AFM), angle-resolved X-ray photoelectron spectroscopy (ARXPS) and attenuated total reflectance (ATR) FTIR spectroscopy. Comparative height profile analysis combined with ATR-FTIR studies of the spectral regions characteristic of carboxylic groups and C1s core level envelope by XPS confirmed specific interactions between LPSQ-COOH and mica.

Novel blends of polylactide with ethylene glycol derivatives of POSS.

Polylactide (PLA), a main biodegradable and biobased candidate for the replacement of petrochemical polymers, is stiff and brittle at room conditions. It is therefore of high interest to formulate new PLA-based materials suitable for applications demanding flexibility and toughness. In this work, novel blends of PLA with polyhedral oligomeric silsesquioxanes (POSS) grafted with longer (P1) and shorter (P2) arms of ethylene glycol derivatives were prepared and studied. It was hypothesized that, owing to their architecture with the central POSS cage grafted with arms, miscibility and stability of the blends could be improved. Indeed, PLA/P1 blends were homogeneous despite P1 relatively high Mw of 9,500 g mol-1. The blend with 20 wt% of P1, having Tg at 16 °C, was transparent and flexible, elastomer-like material with excellent drawability. The blend remained homogeneous and retained its good drawability as well as flexibility during 6 months of aging at room temperature: a 2 % secant modulus of elasticity well below 100 MPa, a low yield stress below 2 MPa, and and a large strain at break of 8 (800 %). Contary to that, PLA/P2 blends were only partially miscible. Nevertheless, owing to the liquid state of the dispersed phase, the blend with 15 wt% of P2 was transparent and ductile, with Tg at 49 °C, a relatively high yield strength of 29 MPa, and a large strain at break of 2.3 (230 %). The toughening mechanism involved the initiation of crazes and facilitation of their propagation by the liquid inclusions via the local plasticization effect.