Altitudinal variation of microplastic abundance in lakeshore sediments from Italian lakes.

Microplastic (MP) contamination represents an issue of global concern for both aquatic and terrestrial ecosystems, but only in recent years, the study of MPs has been focused on freshwaters. Several monitoring surveys have detected the presence of a wide array of MPs differing in size, shape, and polymer composition in rivers and lakes worldwide. Because of their role of sink for plastic particles, the abundance of MPs was investigated in waters, and deep and shoreline sediments from diverse lakes, confirming the ubiquity of this contamination. Although diverse factors, including those concerning anthropogenic activities and physical characteristics of lakes, have been supposed to affect MP abundances, very few studies have directly addressed these links. Thus, the aim of the present study was to explore the levels of MP contamination in mountain and subalpine lakes from Northern Italy. Fourteen lakes dislocated at different altitudes and characterized by dissimilar anthropic pressures were visited. Lakeshore sediments were collected close to the drift line to assess MPs contamination. Our results showed the presence of MPs in lakeshore sediments from all the lakes, with a mean (± standard deviation) expressed as MPs/Kg dry sediment accounting to 14.42 ± 13.31 (range 1.57-61.53), while expressed as MPs/m2, it was 176.07 ± 172.83 (range 25.00-666.67). The MP abundance measured for Garda Lake was significantly higher compared to all the other ones (F1,13 = 7.344; P < 0.001). The pattern of contamination was dominated by fibers in all the lakes, but they were the main contributors in mountain lakes. These findings showed that the MP abundance varied according to the altitude of the lakes, with higher levels measured in subalpine lakes located at low altitudes and surrounded by populated areas.

Exposure to Microplastics Made of Plasmix-Based Materials at Low Amounts Did Not Induce Adverse Effects on the Earthworm Eisenia foetida.

The implementation of recycling techniques represents a potential solution to the plastic pollution issue. To date, only a limited number of plastic polymers can be efficiently recycled. In the Italian plastic waste stream, the residual, non-homogeneous fraction is called 'Plasmix' and is intended for low-value uses. However, Plasmix can be used to create new materials through mechanical recycling, which need to be tested for their eco-safety. This study aimed to investigate the potential toxicity of two amounts (0.1% and 1% MPs in soil weight) of microplastics (MPs) made of naïve and additivated Plasmix-based materials (Px and APx, respectively) on the earthworm Eisenia foetida. Changes in oxidative status and oxidative damage, survival, gross growth rate and reproductive output were considered as endpoints. Although earthworms ingested both MP types, earthworms did not suffer an oxidative stress condition or growth and reproductive impairments. The results suggested that exposure to low amounts of both MPs can be considered as safe for earthworms. However, further studies testing a higher amount or longer exposure time on different model species are necessary to complete the environmental risk assessment of these new materials.

Toward chemical recycling of PU foams: study of the main purification options.

The recovery of the polyol component, after glycolysis of polyurethane (PU) foams coming from automotive waste, was investigated. Several separation methods such as simple sedimentation, centrifugation and liquid-liquid extraction, eventually preceded by an acid washing step, were tested. The obtained fractions were characterized by infrared spectroscopy and CHN elemental analysis. Furthermore, multivariate data analysis was carried out on the infrared spectra by principal component analysis to classify the fractions based on purity. IR spectroscopy coupled with principal component analysis was able to estimate the success of the separation and eventual culprits such as contaminations, which were then quantified by CHN elemental analysis. This approach addresses some critical limitations associated with classical analytical techniques such as NMR, TGA, GPC, MALDI-TOF that often require an extremely accurate separation of the depolymerized product fractions. Moreover, IR spectroscopy and CHN elemental analysis techniques are cheap and widespread in standard materials science laboratories. At last, based on the results of the analysis of the regenerated polyol fractions, and on the foaming tests, considerations were made to guide the choice of the purification method according to the application specifications and greenness.

Thymus vulgaris Essential Oil in Beta-Cyclodextrin for Solid-State Pharmaceutical Applications.

Antimicrobial resistance related to the misuse of antibiotics is a well-known current topic. Their excessive use in several fields has led to enormous selective pressure on pathogenic and commensal bacteria, driving the evolution of antimicrobial resistance genes with severe impacts on human health. Among all the possible strategies, a viable one could be the development of medical features that employ essential oils (EOs), complex natural mixtures extracted from different plant organs, rich in organic compounds showing, among others, antiseptic properties. In this work, green extracted essential oil of Thymus vulgaris was included in cyclic oligosaccharides cyclodextrins (CD) and prepared in the form of tablets. This essential oil has been shown to have a strong transversal efficacy both as an antifungal and as an antibacterial agent. Its inclusion allows its effective use because an extension of the exposure time to the active compounds is obtained and, therefore, a more marked efficacy, especially against biofilm-producing microorganisms such as P. aeruginosa and S. aureus, was registered. The efficacy of the tablet against candidiasis opens their possible use as a chewable tablet against oral candidiasis and as a vaginal tablet against vaginal candidiasis. Moreover, the registered wide efficacy is even more positive since the proposed approach can be defined as effective, safe, and green. In fact, the natural mixture of the essential oil is produced by the steam current method; therefore, the manufacturer employs substances that are not harmful, with very low production and management costs.

Extracts from Cabbage Leaves: Preliminary Results towards a "Universal" Highly-Performant Antibacterial and Antifungal Natural Mixture.

As dramatically experienced in the recent world pandemic, viral, bacterial, fungal pathogens constitute very serious concerns in the global context of human health. Regarding this issue, the World Health Organization has promoted research studies that aim to develop new strategies using natural products. Although they are often competitive with synthetic pharmaceuticales in clinical performance, they lack their critical drawbacks, i.e., the environmental impact and the high economic costs of processing. In this paper, the isolation of a highly performant antibacterial and antifungal lipophilic natural mixture from leaves of savoy and white cabbages is proposed as successful preliminary results for the valorization of agricultural waste produced in cabbage cultivation. The fraction was chemically extracted from vegetables with diethyl ether and tested against two Candida species, as well as Pseudomonas aeruginosa, Klebsiella pneumoniae and Staphylococcus aureus reference strains. All the different fractions (active and not active) were chemically characterized by vibrational FT-IR spectroscopy and GC-MS analyses. The extracts showed high growth-inhibition performance on pathogens, thus demonstrating strong application potential. We think that this work, despite being at a preliminary stage, is very promising, both from pharmaceutical and industrial points of view, and can be proposed as a proof of concept for the recovery of agricultural production wastes.

Microplastic contamination of supraglacial debris differs among glaciers with different anthropic pressures.

Microplastic (MP) contamination is ubiquitous and widespread in terrestrial and aquatic ecosystems, including remote areas. However, information on the presence and distribution of MPs in high-mountain ecosystems, including glaciers, is still limited. The present study aimed at investigating presence, spatial distribution, and patterns of contamination of MPs on three glaciers of the Ortles-Cevedale massif (Central Alps, Northern Italy) with different anthropic pressures, i.e., the Forni, Cedec and Ebenferner-Vedretta Piana glaciers. Samples of supraglacial debris were randomly collected from the glaciers and MPs were isolated. The mean amount (±SE) of MPs measured in debris from Forni, Cedec and Ebenferner-Vedretta Piana glaciers was 0.033 ± 0.007, 0.025 ± 0.009, and 0.265 ± 0.027 MPs g-1 dry weight, respectively. The level and pattern of MP contamination from the Ebenferner-Vedretta Piana glacier were significantly different from those of the other glaciers. No significant spatial gradient in MP distribution along the ablation areas of the glaciers was observed, suggesting that MPs do not accumulate toward the glacier snout. Our results confirmed that local contamination can represent a relevant source of MPs in glacier ecosystems experiencing high anthropic pressure, while long-range transport can be the main source on other glaciers.

The hidden cost of following currents: Microplastic ingestion in a planktivorous seabird.

Microplastics are increasingly pervasive pollutants, particularly abundant in the neuston where they drift with currents. We assessed dietary microplastic ingestion in the Mediterranean storm petrel (Hydrobates pelagicus melitensis), a small pelagic seabird that forages on plankton and inhabit the Mediterranean sea, one of the most polluted seas worldwide. We collected spontaneous regurgitates from 30 chick-rearing individuals and used GPS tracking data from 7 additional individuals to locate foraging areas. Birds foraged in pelagic areas characterized by water stirring and mixing, and regurgitates from 14 individuals (i.e. 45 %) contained microplastics. Fibers were the dominant shape (56 %), with polyester, polyethylene and nylon being the most frequent polymers. Our findings highlight the potential sensitivity of this species of conservation interest to plastic pollution and suggest that storm petrel regurgitates can be a valuable matrix to investigate microplastic ingestion in planktonic foragers, providing a characterization of spatio-temporal patterns of microplastic exposure in pelagic environments.

Analytical Characterization of the Intercalation of Neutral Molecules into Saponite.

Organo-modified layered materials characterization poses challenges due to their complexity and how other aspects such as contamination, preparation methods and degree of intercalation influence the properties of these materials. Consequently, a deep understanding of their interlayer organization is of utmost importance to optimize their applications. These materials can in fact improve the stability of photoactive molecules through intercalation, avoiding the quenching of their emission at the solid state, to facilitate their use in sensors or other devices. Two synthetic methods for the preparation of saponites with a cationic surfactant (CTABr) and a neutral chromophore (Fluorene) were tested and the obtained products were initially characterized with several complementary techniques (XRPD, SEM, TGA, IR, UV-Vis, Fluorescence and Raman spectroscopy), but a clear understanding of the organization of the guest molecules in the material could not be obtained by these techniques alone. This information was obtained only by thermogravimetry coupled with gas chromatography and mass spectroscopy (TGA-GC-MS) which allowed identifying the species present in the sample and the kind of interaction with the host by distinguishing between intercalated and adsorbed on the surface.

Quantification of molecular weight discrimination in grafting to reactions from ultrathin polymer films by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

In the present study, a reliable and robust method was developed to quantify the molecular weight discrimination that can occur in grafting to reactions via indirect MALDI-TOF quantification of the molecular weights of grafted chains by comparing the characteristics of the polymeric material before the grafting reaction with those of the unreacted material recovered after grafting. Two polystyrene samples with different molecular weights and narrow molecular weight distributions were employed to prepare model blends that were grafted to silicon wafers and an analytical method was developed and validated to assess and quantify the modification of the molecular weight distribution that takes place during the grafting to process. Particular attention was paid to the standardization of the sample treatment and to find the best data collection and calibration methodologies in order to have statistically significant data even in the presence of a very scarce amount of the sample. Furthermore, to evaluate the accuracy of the analytical procedure, the lack of suitable standard and certified materials required a further experiment to be carried out by comparing the new optimized MALDI-TOF method and direct measurements using TGA-GC-MS on a model blend containing deuterated and hydrogenated polystyrene samples with appropriate molecular weights and distributions. The optimized method was applied on samples obtained by a thermally induced grafting to reaction from ultrathin polymer films and, for the first time, to our knowledge, an enrichment effect occurring in the ultrathin grafted layer obtained from a melt was evidenced.

Low-Cost Biobased Coatings for AM60 Magnesium Alloys for Food Contact and Harsh Environment Applications.

Low-cost, environmentally friendly and easily applicable coating for Mg alloys, able to resist in real world conditions, are studied. Coatings already used for other metals (aluminum, steel) and never tested on Mg alloy for its different surface and reactivity were deposited on AM60 magnesium alloys to facilitate their technological applications, also in presence of chemically aggressive conditions. A biobased PA11 powder coating was compared to synthetic silicon-based and polyester coatings, producing lab scale samples, probed by drop deposition tests and dipping in increasingly aggressive, salty, basic and acid solutions, at RT and at higher temperatures. Coatings were analyzed by SEM/EDX to assess their morphology and compositions, by optical and IR-ATR microscopy analyses, before and after the drop tests. Migration analyses from the samples were performed by immersion tests using food simulants followed by ICP-OES analysis of the recovered simulant to explore applications also in the food contact field. A 30 µm thick white lacquer and a 120 µm PA11 coating resulted the best solutions. The thinner siliconic and lacquer coatings, appearing brittle and thin in the SEM analysis, failed some drop and/or dipping test, with damages especially at the edges. The larger thickness is thus the unique solution for edgy or pointy samples. Finally, coffee cups in AM60 alloy were produced, as real word prototypes, with the best performing coatings and tested for both migration by dipping, simulating also real world aging (2 h in acetic acid at 70° and 24 h in hot coffee at 60 °C): PA11 resulted stable in all the tests and no migration of toxic metals was observed, resulting a promising candidate for many real world application in chemically aggressive environments and also food and beverage related applications.

Microplastic Contamination in Snow from Western Italian Alps.

Recent studies have documented the presence of microplastics (MPs) in remote areas, including soils or sediments collected in mountain and glacier environments, but information on their presence in snow is scant. The present study aimed at exploring the presence of MPs in residual snow collected in four locations of the Aosta Valley (Western Italian Alps), with different accessibility and human presence. Overall, the µ-FTIR analyses confirmed the presence of 18 MPs in snow, 7 (39%) items were fibres, while 11 (61%) were fragments. Polyethylene (PE; 7 MPs) was the main polymer, followed by polyethylene terephthalate (PET; 3 MPs), high density PE (HDPE; 3 MPs), polyester (2 MPs), while only 1 MP made by low density PE, polypropylene and polyurethane were found. The mean (± SE) concentration of MPs in snow ranged between 0.39 ± 0.39 MPs/L and 4.91 ± 2.48 MPs/L, with a mean of 2.32 ± 0.96 MPs/L for the sampling locations. The concentration of MPs did not statistically differ among locations. Our results suggest that MPs presence in high-mountain ecosystems might depend on deposition through atmospheric precipitations or local sources due to human activities. For these reasons, policies aiming at reducing plastic use and dispersal in mountain areas may be effective in preventing local MP contamination.

Effect of Trapped Solvent on the Interface between PS-b-PMMA Thin Films and P(S-r-MMA) Brush Layers.

The orientation of block copolymer (BCP) features in thin films can be obtained by spin-coating a BCP solution on a substrate surface functionalized by a polymer brush layer of the appropriate random copolymer (RCP). Although this approach is well established, little work reporting the amount and distribution of residual solvent in the polymer film after the spin-coating process is available. Moreover, no information can be found on the effect of trapped solvent on the interface between the BCP film and RCP brush. In this work, systems consisting of poly(styrene)-b-poly(methyl methacrylate) thin films deposited on poly(styrene-r-methyl methacrylate) brush layers are investigated by combining neutron reflectivity (NR) experiments with simulation techniques. An increase in the amount of trapped solvent is observed by NR as the BCP film thickness increases accompanied by a significant decrease of the interpenetration length between the BCP and RCP, thus suggesting that the interpenetration between grafted chains and block copolymer chains is hampered by the solvent. Hybrid particle-field molecular dynamics simulations of the analyzed system confirm the experimental observations and demonstrate a clear correlation between the interpenetration length and the amount of trapped solvent.

Effect of shell structure of Ti-immobilized metal ion affinity chromatography core-shell magnetic particles for phosphopeptide enrichment.

Magnetic materials in sample preparation for shotgun phosphoproteomics offer several advantages over conventional systems, as the enrichment can be achieved directly in solution, but they still suffer from some drawbacks, due to limited stability and selectivity, which is supposed to be affected by the hydrophilicity of the polymeric supports used for cation immobilization. The paper describes the development of an improved magnetic material with increased stability, thanks to a two-step covering of the magnetic core, for the enrichment of phosphopeptides in biological samples. Four materials were prepared featuring a polymeric shell with tunable hydrophilicity, obtained by "grafting from" polymerization of glycidyl methacrylate with 0-8.3% of polyethylene glycol methacrylate (PEGMA), the latter used to modulate the hydrophilicity of the material surface. Finally, the materials were functionalized with iminodiacetic acid for Ti4+ ion immobilization. The materials were analyzed for their composition by a combination of CHN elemental analysis and thermogravimetric analysis, also hyphenated to gas chromatography and mass spectrometric detection. Surface characteristics were evaluated by water contact angle measurements, scanning electron microscopy and energy dispersive X-ray spectrometry. These materials were applied to the enrichment of phosphopeptides from yeast protein digests. Peptides were identified by proteomics techniques using nano-high performance liquid chromatography coupled to mass spectrometry and bioinformatics. Qualitatively the peptides identified by the four systems were comparable, with 1606-1693 phosphopeptide identifications and a selectivity of 47-54% for all materials. The physico-chemical features of the identified peptides were also the same for the four materials. In particular, the grand average of hydropathy index values indicated that the enriched phosphopeptides were hydrophilic (ca. 90%), and only some co-enriched non-phosphorylated peptides were hydrophobic (21-28%), regardless of the material used for enrichment. Peptides had a pI ≤ 7, which indicated a well-known bias for acidic peptides binding, attributed to the interaction with the metal center itself. The results indicated that the enrichment of phosphopeptides and the co-enrichment of non-phosphorylated peptides is mainly driven by interactions with Ti4+ and does not depend on the amount of PEGMA chains in the polymer shell.

New Hints on the Maya Blue Formation Process by PCA-Assisted In Situ XRPD/PDF and Optical Spectroscopy.

The exact recipe to prepare the ancient Maya Blue (MB), an incredibly resistant and brilliant pigment prepared from indigo (dye) and Palygorskite (clay), is lost to the ages. To unravel the key features of the MB formation process, several inorganic-dye couples were heated to 200 °C and cooled to RT, to investigate their reactivity and the diffusion and degree of sequestration of the dye into the inorganic host. In situ XRPD/PDF and fiber optic reflectance spectroscopy (FORS) data, along with TGA, provided a comprehensive overview on MB formation mechanism. XRPD/PDF gave information on long/short range behaviors of water desorption/adsorption and indigo sequestration, while TGA and in situ FORS gave information on mass and optical changes within temperature. Ex situ dye removal was used to understand the sample stability after the thermal treatment. A statistical approach based on principal component analysis was exploited to efficiently and jointly analyze the ≈3000 collected patterns. MB formation starts below 110 °C with disordered distribution of indigo within the channels, reaching maximum reaction speed and higher ordering at 150 °C. Above 175 °C, color changes and a stronger sequestration of indigo into framework channels are observed, whereas the affinity for water is dramatically reduced. The origin of different colors, hues, and stability in historical MB samples can then be explained in terms of different thermal histories of the starting mechanical indigo/palygorskite mixtures.

Wine evolution during bottle aging, studied by 1H NMR spectroscopy and multivariate statistical analysis.

The study of wine evolution during bottle aging is an important aspect of wine quality. Ten different red wines (Vitis vinifera) from Piedmont region were analysed 3 months after bottling and after a further 48 month conservation in a climate controlled wine cellar kept at a constant/controlled temperature of 12 °C. Two white wines (Vitis vinifera) were included in this study for comparison purposes. White wines were analysed 3 months after bottling and after further 24 months of bottle aging in the same climate controlled wine cellar. Metabolite changes during this period were evaluated using 1H NMR spectroscopy combined with statistical analysis. Metabolite variations due to wine aging were minimal compared to those that resulted from a different wine type and wine geographical origin. Therefore, it was necessary to remove this source of variability to discriminate between fresh and refined samples. The storage at low and controlled temperature for 2 or 4 years permitted a slow but progressive evolution of all wines under investigation. 1H NMR spectroscopy, implemented with statistical data analysis, allowed identifying and differentiating wine samples from the two aging stages. In most wines, a decrease in organic acids (lactic acid, succinic acid and tartaric acid) and an increase in esters (ethyl acetate and ethyl lactate) was observed. Catechin and epicatechin decreased during aging in all wines while gallic acid increased in almost all red wines.

Relaxation Dynamics in Polyethylene Glycol/Modified Hydrotalcite Nanocomposites.

Polyethylene glycol-based nanocomposites containing an organo-modified hydrotalcite with loadings ranging from 0.5 to 5 wt.% were prepared by melt mixing performed just above the melting point of the polymer matrix. In these conditions, the dispersion of the nanofiller within the polymer matrix was quite homogeneous as revealed by TEM analyses. The effect of various thermal treatments and filler loadings was thoroughly investigated by means of rheological, morphological and gas chromatography-mass spectrometry, hyphenated to thermogravimetry analysis tests. Unfilled polyethylene glycol exhibited a continuous decrease in complex viscosity upon heating. In contrast, the complex viscosity of nanocomposites containing nanofiller loadings higher than 1 wt.% showed first a decrease, followed by an increase in the complex viscosity as the temperature increases, exhibiting a minimum between 130 and 140 °C. Annealing at 180 °C for different times further increased the viscosity of the system. This unusual behavior was explained by the occurrence of grafting reactions between the ⁻OH terminal groups of the polyethylene glycol chains and the hydroxyl groups of the organo-modified filler, thus remarkably affecting the relaxation dynamics of the system.

Control of Doping Level in Semiconductors via Self-Limited Grafting of Phosphorus End-Terminated Polymers.

An effective bottom-up technology for precisely controlling the amount of dopant atoms tethered on silicon substrates is presented. Polystyrene and poly(methyl methacrylate) polymers with narrow molecular weight distribution and end-terminated with a P-containing moiety were synthesized with different molar mass. The polymers were spin coated and subsequently end-grafted onto nondeglazed silicon substrates. P atoms were bonded to the surface during the grafting reaction, and their surface density was set by the polymer molar mass, according to the self-limiting nature of the "grafting to" reaction. Polymeric material was removed by O2 plasma hashing without affecting the tethered P-containing moieties on the surface. Repeated cycles of polymer grafting followed by plasma hashing led to a cumulative increase, at constant steps, in the dose of P atoms grafted to the silicon surface. P injection in the silicon substrate was promoted and precisely controlled by high-temperature thermal treatments. Sheet resistance measurements demonstrated effective doping of silicon substrate.

New Ti-IMAC magnetic polymeric nanoparticles for phosphopeptide enrichment from complex real samples.

The work describes the preparation of a new magnetic phase for batch enrichment of phosphopeptides. The material exploits the advantages of magnetic solid phase extraction and couples them with the most employed approach for phosphopeptide enrichment, i.e. Ti4+-IMAC. In order to immobilize Ti4+ ions on the surface of the magnetite nanoparticles, they were first covered by a silica shell and then modified to expose at the surface bromine containing groups. Glycidyl methacrylate was subsequently polymerized from these groups using the "grafting from" approach by the activator regenerated by electron transfer-atom transfer radical polymerization (ARGET-ATRP) technique. Finally, the glycidyl groups were reacted with iminodiacetic acid to functionalize the material with moieties suitable for coordination. The prepared material was extensively characterized and subsequently tested for enrichment of a bovine serum albumin mixture with casein to ascertain its potential. With positive results, the new magnetic polymeric material was further employed to set up an enrichment method on yeast protein digest based on shotgun proteomics. The sample to phase ratio was optimized and the best condition compared to a commercial TiO2 spin column. At the end of the comparison, the new material proved better and could enrich a larger total number of phosphopeptides with increased selectivity. All these conclusions and the test performed on a real complex sample within the final shotgun application further support the applicability of the new material in phosphopeptide analysis of real matrices.

Toward Lateral Length Standards at the Nanoscale Based on Diblock Copolymers.

The self-assembly (SA) of diblock copolymers (DBCs) based on phase separation into different morphologies of small and high-density features is widely investigated as a patterning and nanofabrication technique. The integration of conventional top-down approaches with the bottom-up SA of DBCs enables the possibility to address the gap in nanostructured lateral length standards for nanometrology, consequently supporting miniaturization processes in device fabrication. On this topic, we studied the pattern characteristic dimensions (i.e., center-to-center distance L0 and diameter D) of a cylinder-forming polystyrene-b-poly( methyl methacrylate) PS-b-PMMA (54 kg mol-1, styrene fraction 70%) DBC when confined within periodic SiO2 trenches of different widths (W, ranging between 75 and 600 nm) and fixed length (l, 5.7 µm). The characteristic dimensions of the PMMA cylinder structure in the confined configurations were compared with those obtained on a flat surface (L0 = 27.8 ± 0.5 nm, D = 13.0 ± 1.0 nm). The analysis of D as a function of W evolution indicates that the eccentricity of the PMMA cylinders decreases as a result of the deformation of the cylinder in the direction perpendicular to the trenches. The center-to-center distance in the direction parallel to the long side of the trenches (L0l) is equal to L0 measured on the flat surface, whereas the one along the short side (L0w) is subjected to an appreciable variation (ΔL0w = 5 nm) depending on W. The possibility of finely tuning L0w maintaining constant L0l paves the way to the realization of a DBC-based transfer standard for lateral length calibration with periods in the critical range between 20 and 50 nm wherein no commercial transfer standards are available. A prototype transfer standard with cylindrical holes was used to calibrate the linear correction factor c(Δx')xx' of an atomic force microscope for a scan length of Δx' = 1 µm. The relative standard uncertainty of the correction factor was only 1.3%, and the second-order nonlinear correction was found to be significant.

Effect of Entrapped Solvent on the Evolution of Lateral Order in Self-Assembled P(S-r-MMA)/PS-b-PMMA Systems with Different Thicknesses.

Block copolymers (BCPs) are emerging as a cost-effective nanofabrication tool to complement conventional optical lithography because they self-assemble in highly ordered polymeric templates with well-defined sub-20-nm periodic features. In this context, cylinder-forming polystyrene-block-poly(methyl methacrylate) BCPs are revealed as an interesting material of choice because the orientation of the nanostructures with respect to the underlying substrate can be effectively controlled by a poly(styrene-random-methyl methacrylate) random copolymer (RCP) brush layer grafted to the substrate prior to BCP deposition. In this work, we investigate the self-assembly process and lateral order evolution in RCP + BCP systems consisting of cylinder-forming PS-b-PMMA (67 kg mol-1, PS fraction of ∼70%) films with thicknesses of 30, 70, 100, and 130 nm deposited on RCP brush layers having thicknesses ranging from 2 to 20 nm. The self-assembly process is promoted by a rapid thermal processing machine operating at 250 °C for 300 s. The level of lateral order is determined by measuring the correlation length (ξ) in the self-assembled BCP films. Moreover, the amount of solvent (Φ) retained in the RCP + BCP systems is measured as a function of the thicknesses of the RCP and BCP layers, respectively. In the 30-nm-thick BCP films, an increase in Φ as a function of the thickness of the RCP brush layer significantly affects the self-assembly kinetics and the final extent of the lateral order in the BCP films. Conversely, no significant variations of ξ are observed in the 70-, 100-, and 130-nm-thick BCP films with increasing Φ.