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Abstract

O objetivo deste trabalho foi avaliar os efeitos da modificação da atmosfera na embalagem sobre a qualidade de frutos de mangaba (Hancornia speciosa Gomes), armazenados sob refrigeração (11 ± 1°C), em filmes de policloreto de vinila ou polietileno de baixa densidade, com ou sem permanganato de potássio. Independentemente do tipo de filme, a acidez titulável e o teor de sólidos solúveis aumentaram, enquanto o pH diminuiu, ao longo do período de armazenamento. Durante todo o tempo de armazenamento, os frutos refrigerados sob atmosfera modificada tiveram valores mais altos para a relação sólidos solúveis/acidez titulável do que os outros frutos. Ocorreu significativa perda de massa fresca nos frutos embalados em policloreto de vinila, relativamente àqueles embalados em polietileno de baixa densidade. Os frutos sob atmosfera modificada por filme de policloreto de vinila, com ou sem permanganato de potássio, e por filme de polietileno de baixa densidade, com permanganato de potássio, mantiveram um bom aspecto geral, até o oitavo dia de armazenamento. Por outro lado, os frutos embalados com polietileno de baixa densidade, sem permanganato de potássio, somente mantiveram este aspecto até o quarto dia de armazenamento. Não houve ataque visível de microrganismos em quaisquer das amostras, durante os dez dias de armazenamento. PALAVRAS-CHAVE: Hancornia speciosa; embalagem; vida-de-prateleira. The objective of this study was to evaluate the effects of packing atmosphere alteration on the mangaba fruits quality (Hancornia speciosa Gomes), stored under refrigeration (11 ± 1°C), using polyvinyl chloride or low density polyethylene films, with or without potassium permanganate. Regardless the kind of film, the titratable acidity and soluble solids content increased, while the pH decreased, along the storage period. During that time, under modified atmosphere and refrigeration, fruits showed higher values for the soluble solids/titrable acidity ratio than other fruits. A significant loss of fresh matter occurred for the fruits packed with polyvinyl chloride, in relation to those packed with low density polyethylene. The fruits under atmosphere modified by polyvinyl chloride film, with or without potassium permanganate, and by low density polyethylene, with potassium permanganate, maintained good general features, until the eighth storage day. However, the fruits packed with low density polyethylene, without potassium permanganate, maintained their good features only until the fourth storage day. During ten storage days, none of the samples were visibly attacked by microorganisms. KEY-WORDS: Hancornia speciosa; packaging; shelf life.

The propagation of long surface water waves over an undulating bed is governed by a Mathieu equation. Instabilities of solutions of this equation indicate resonant interactions associated with the strong reflection of the surface waves by the bedforms. The strongest interaction occurs when the bed wavenumber (l) is approximately twice the surface wavenumber (k). This interaction is known in solid-state physics as Bragg reflection. In this paper the interaction of incident surface waves with a patch of ripples on an otherwise flat bed is considered. For the general nonresonant case (l ≠ 2k), a perturbation solution of the Mathieu equation is obtained. This solution indicates that the reflection coefficient R, defined as the ratio of the magnitudes of the reflected and incident waves, is both oscillatory in the ratio of the overall length of the ripple patch to the surface wavelength and also resonant in the vicinity of l = 2k. The condition of exact resonance (l = 2k) is studied separately and the solution obtained predicts that R tends uniformly to unity as the number of ripples (having l = 2k) is increased. The present approach is simpler and more readily applicable than the use of previous more complicated methods based on potential theory. It also provides some insight into the higher-order resonant interactions between waves on a free surface and an undulating bed. The results are particularly important in oceanography, in connection with the reflection of incident surface waves by sandbars off beaches. [ABSTRACT FROM AUTHOR]

Dense suspensions are materials with broad applications both in industrial processes (e.g. waste disposal, concrete, drilling muds, metalworking chip transport, and food processing) and in natural phenomena (e.g. flows of slurries, debris, and lava). Despite its long research history and its practical relevance, the mechanics of dense suspensions remain poorly understood. The major difficulty is that the grains interact both by hydrodynamic interactions through the liquid and by mechanical contact. These systems thus belong to an intermediate regime between pure suspensions and granular flows. We show that we can unify suspension and granular rheology under a common framework by transferring the frictional approach of dry granular media to wet suspensions of spherical particles. We also discuss non-Newtonian behavior such as normal-stress differences and shear-induced migration. Beyond the classical problem of dense suspension of hard spheres which is far from being completely resolved, there are also entirely novel avenues of study concerning more complex mixtures of particles and fluids such as those involving other types of particles (e.g. fibers) or non-Newtonian fluids that we will also address.

Biofouling on marine surfaces causes immense material and financial harm for maritime vessels and related marine industries. Previous reports have shown the effectiveness of amphiphilic coating systems based on poly(dimethylsiloxane) (PDMS) against such marine foulers. Recent studies on biofouling mechanisms have also demonstrated acidic microenvironments in biofilms and stronger adhesion at low-pH conditions. This report presents the design and utilization of amphiphilic polymer coatings with buffer functionalities as an active disruptor against four different marine foulers. Specifically, this study explores both neutral and zwitterionic buffer systems for marine coatings, offering insights into coating design. Overall, these buffer systems were found to improve foulant removal, and unexpectedly were the most effective against the diatom Navicula incerta .

In this work, two structurally different monoamines (trimethylamine [TMA] and N-methylpiperidine [N-MPip]) are used for the amination of a g-VBC-15 graft copolymer, obtained by the functionalization of a mechanically robust, commercially available styrene-butadiene block copolymer (SB) with vinylbenzyl chloride (VBC) via solution free-radical polymerization. Results demonstrate that g-VBC-15-based membranes quaternized with TMA have superior electrochemical performance than N-MPip counterparts; while, the mechanical properties are good and only slightly inferior to those of N-MPip. Therefore, TMA is the selected monoamine to be alternatively mixed with two polyamines (tetramethyl-1,3-propanediamine [TMPDA] and N,N,N',N'',N''-pentamethyldiethylenetriamine [PMDETA]) into different proportions, in order to modulate the average functionality of the amination mixture in terms of number of amine functional groups available for the quaternization reaction of the membranes. g-VBC-15-based membranes derived therefrom are extensively characterized to assess their thermal, mechanical, and ex situ electrochemical properties. Results indicate that membranes quaternized with a TMA/PMDETA mixture (90:10 in mole) display the highest conductivity among all the investigated membranes aminated with polyamine-based mixtures. Moreover, they have comparable mechanical and electrochemical properties to those quaternized with TMA, while exhibiting a reduced water uptake., (© 2024 Wiley‐VCH GmbH.)

The unique self-assembly properties of unimer micelles are exploited for the preparation of fluorescent nanocarriers embedding hydrophobic fluorophores. Unimer micelles are constituted by a (meth)acrylate copolymer with oligoethyleneglycol and perflurohexylethyl side chains (PEGMA90- co -FA10) in which the hydrophilic and hydrophobic comonomers are statistically distributed along the polymeric backbone. Thanks to hydrophobic interactions in water, the amphiphilic copolymer forms small nanoparticles (<10 nm), with tunable properties and functionality. An easy procedure for the encapsulation of a small hydrophobic molecule (C153 fluorophore) within unimer micelles is presented. UV-vis, fluorescence, and fluorescence anisotropy spectroscopic experimental data demonstrate that the fluorophore is effectively embedded in the nanocarriers. Moreover, the nanocarrier positively contributes to preserve the good emissive properties of the fluorophore in water. The efficacy of the dye-loaded nanocarrier as a fluorescent probe is tested in two-photon imaging of thick ex vivo porcine scleral tissue., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

Amphiphilic copolymer self-assembly is a straightforward approach to obtain responsive micelles, nanoparticles, and vesicles that are particularly attractive for biomedicine, i.e., for the delivery of functional molecules. Here, amphiphilic copolymers of hydrophobic polysiloxane methacrylate and hydrophilic oligo (ethylene glycol) methyl ether methacrylate with different lengths of oxyethylenic side chains were synthesized via controlled RAFT radical polymerization and characterized both thermally and in solution. In particular, the thermoresponsive and self-assembling behavior of the water-soluble copolymers in water was investigated via complementary techniques such as light transmittance, dynamic light scattering (DLS), and small-angle X-ray scattering (SAXS) measurements. All the copolymers synthesized were thermoresponsive, displaying a cloud point temperature ( T cp ) strongly dependent on macromolecular parameters such as the length of the oligo(ethylene glycol) side chains and the content of the SiMA counits, as well as the concentration of the copolymer in water, which is consistent with a lower critical solution temperature (LCST)-type behavior. SAXS analysis revealed that the copolymers formed nanostructures in water below T cp , whose dimension and shape depended on the content of the hydrophobic components in the copolymer. The hydrodynamic diameter ( D h ) determined by DLS increased with the amount of SiMA and the associated morphology at higher SiMA contents was found to be pearl-necklace-micelle-like, composed of connected hydrophobic cores. These novel amphiphilic copolymers were able to modulate thermoresponsiveness in water in a wide range of temperatures, including the physiological temperature, as well as the dimension and shape of their nanostructured assemblies, simply by varying their chemical composition and the length of the hydrophilic side chains.

In this work, a commercial SBS was functionalized with the 2,2,6,6-tetramethylpiperidin- N -oxyl stable radical (TEMPO) via free-radical activation initiated with benzoyl peroxide (BPO). The obtained macroinitiator was used to graft both vinylbenzyl chloride (VBC) and styrene/VBC random copolymer chains from SBS to create g-VBC-x and g-VBC-x- co -Sty-z graft copolymers, respectively. The controlled nature of the polymerization as well as the use of a solvent allowed us to reduce the extent of the formation of the unwanted, non-grafted (co)polymer, thereby facilitating the graft copolymer's purification. The obtained graft copolymers were used to prepare films via solution casting using chloroform. The -CH 2 Cl functional groups of the VBC grafts were then quantitatively converted to -CH 2 (CH 3 ) 3 N + quaternary ammonium groups via reaction with trimethylamine directly on the films, and the films, therefore, were investigated as anion exchange membranes (AEMs) for potential application in a water electrolyzer (WE). The membranes were extensively characterized to assess their thermal, mechanical, and ex situ electrochemical properties. They generally presented ionic conductivity comparable to or higher than that of a commercial benchmark as well as higher water uptake and hydrogen permeability. Interestingly, the styrene/VBC-grafted copolymer was found to be more mechanically resistant than the corresponding graft copolymer not containing the styrene component. For this reason, the copolymer g-VBC-5- co -Sty-16-Q with the best balance of mechanical, water uptake, and electrochemical properties was selected for a single-cell test in an AEM-WE.

Two types of amphiphilic random terpolymers, poly(ethylene glycol methyl ether methacrylate)- ran -poly(2,2,6,6-tetramethylpiperidinyloxy methacrylate)- ran -poly(polydimethyl siloxane methacrylate) (PEGMEMA- r -PTMA- r -PDMSMA), were synthesized and evaluated for antifouling (AF) and fouling-release (FR) properties using diverse marine fouling organisms. In the first stage of production, the two respective precursor amine terpolymers containing (2,2,6,6-tetramethyl-4-piperidyl methacrylate) units (PEGMEMA- r -PTMPM- r -PDMSMA) were synthesized by atom transfer radical polymerization using various comonomer ratios and two initiators: alkyl halide and fluoroalkyl halide. In the second stage, these were selectively oxidized to introduce nitroxide radical functionalities. Finally, the terpolymers were incorporated into a PDMS host matrix to create coatings. AF and FR properties were examined using the alga Ulva linza , the barnacle Balanus improvisus , and the tubeworm Ficopomatus enigmaticus . The effects of comonomer ratios on surface properties and fouling assay results for each set of coatings are discussed in detail. There were marked differences in the effectiveness of these systems against the different fouling organisms. The terpolymers had distinct advantages over monopolymeric systems across the different organisms, and the nonfluorinated PEG and nitroxide combination was identified as the most effective formulation against B. improvisus and F. enigmaticus .

Since the banning of tributyltin, the addition of inorganic (metal oxides) and organic (pesticides, herbicides) biocides in antifouling paint has represented an unavoidable step to counteract biofouling and the resulting biodeterioration of submerged surfaces. Therefore, the development of new methods that balance antifouling efficacy with environmental impact has become a topic of great importance. Among several proposed strategies, natural extracts may represent one of the most suitable alternatives to the widely used toxic biocides. Posidonia oceanica is one of the most representative organisms of the Mediterranean Sea and contains hundreds of bioactive compounds. In this study, we prepared, characterized, and assessed a hydroalcoholic extract of P. oceanica and then compared it to three model species. Together, these four species belong to relevant groups of biofoulers: bacteria (Aliivibrio fischeri), diatoms (Phaeodactylum tricornutum), and serpulid polychaetes (Ficopomatus enigmaticus). We also added the same P. oceanica extract to a PDMS-based coating formula. We tested this coating agent with Navicula salinicola and Ficopomatus enigmaticus to evaluate both its biocidal performance and its antifouling properties. Our results indicate that our P. oceanica extract provides suitable levels of protection against all the tested organisms and significantly reduces adhesion of N. salinicola cells and facilitates their release in low-intensity waterflows., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Hydrolyzable block copolymers consisting of a polyethylene glycol (PEG) first block and a random poly(trialkylsilyl methacrylate (TRSiMA, R = butyl, isopropyl)- co -methyl methacrylate (MMA)) second block were synthesized by RAFT polymerization. Two PEGs with different molar masses ( M n = 750 g/mol (PEG1) and 2200 g/mol (PEG2)) were used as macro-chain transfer agents and the polymerization conditions were set in order to obtain copolymers with a comparable mole content of trialkylsilyl methacrylate (~30 mole%) and two different PEG mole percentages of 10 and 30 mole%. The hydrolysis rates of PEG- b -(TRSiMA- co -MMA) in a THF/basic (pH = 10) water solution were shown to drastically depend on the nature of the trialkylsilyl groups and the mole content of the PEG block. Films of selected copolymers were also found to undergo hydrolysis in artificial seawater (ASW), with tunable erosion kinetics that were modulated by varying the copolymer design. Measurements of the advancing and receding contact angles of water as a function of the immersion time in the ASW confirmed the ability of the copolymer film surfaces to respond to the water environment as a result of two different mechanisms: (i) the hydrolysis of the silylester groups that prevailed in TBSiMA-based copolymers; and (ii) a major surface exposure of hydrophilic PEG chains that was predominant for TPSiMA-based copolymers. AFM analysis revealed that the surface nano-roughness increased upon immersion in ASW. The erosion of copolymer film surfaces resulted in a self-polishing, antifouling behavior against the diatom Navicula salinicola . The amount of settled diatoms depended on the hydrolysis rate of the copolymers.

Microplastic (MP) pollution represents a distinctive mark of the Anthropocene. Despite the increasing efforts to determine the ecological impacts of MP on marine biodiversity, our understanding of their toxicological effects on invertebrate species is still limited. Despite their key functional roles, sponges (Phylum Porifera) are particularly understudied in MP research. These filter-feeders extract and retain particles from the water column, across a broad size range. In this study, we carried out a laboratory experiment to assess the uptake of MPs (polyethylene, PE) by the Mediterranean sponge Petrosia ficiformis, how MPs influence key biological process after different times of exposure (24h and 72h) and whether they can be subsequently eliminated. MP uptake increased with time of exposure, with 30.6% of the inoculated MP particles found in sponge samples after 72h. MPs impaired filtration and respiration rates and these effects were still evident 72h after sponges had been transferred in uncontaminated water. Our study shows that time of exposure represents a key factor in determining MP toxicity in sponges. In addition, our results suggest that sponges are able to incorporate foreign particles and may thus be a potential bioindicator for MP pollutants., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Water-soluble amphiphilic random copolymers composed of tri(ethylene glycol) methacrylate (TEGMA) or poly(ethylene glycol) methyl ether methacrylate (PEGMA) and perfluorohexylethyl acrylate (FA) were synthesized by ARGET-ATRP, and their self-assembling and thermoresponsive behavior in water was studied by dynamic light scattering (DLS) and UV-vis spectroscopy. The copolymer ability to self-fold in single-chain nano-sized structures (unimer micelles) in aqueous solutions was exploited to encapsulate Combretastatin A-4 (CA-4), which is a very hydrophobic anticancer drug. The cloud point temperature ( T cp ) was found to linearly decrease with increasing drug concentration in the drug/copolymer system. Moreover, while CA-4 was preferentially incorporated into the unimer micelles of TEGMA- ran -FA, the drug was found to induce multi-chain, submicro-sized aggregation of PEGMA- ran -FA. Anyway, the encapsulation efficiency was very high (≥81%) for both copolymers. The drug release was evaluated in PBS aqueous solutions both below and above T cp for TEGMA- ran -FA copolymer and below T cp , but at two different drug loadings, for PEGMA- ran -FA copolymer. In any case, the release kinetics presented similar profiles, characterized by linear trends up to ≈10-13 h and ≈7 h for TEGMA- ran -FA and PEGMA- ran -FA, respectively. Then, the release rate decreased, reaching a plateau. The release from TEGMA- ran -FA was moderately faster above T cp than below T cp , suggesting that copolymer thermoresponsiveness increased the release rate, which occurred anyway by diffusion below T cp . Cytotoxicity tests were carried out on copolymer solutions in a wide concentration range (5-60 mg/mL) at 37 °C by using Balb/3T3 clone A31 cells. Interestingly, it was found that the concentration-dependent micro-sized aggregation of the amphiphilic random copolymers above T cp caused a sort of "cellular asphyxiation" with a loss of cell viability clearly visible for TEGMA- ran -FA solutions ( T cp below 37 °C) with higher copolymer concentrations. On the other hand, cells in contact with the analogous PEGMA- ran -FA ( T cp above 37 °C) presented a very good viability (≥75%) with respect to the control at any given concentration.

Many synthetic polymers used to form polymer-brush films feature a main backbone with functional, oligomeric side chains. While the structure of such graft polymers mimics biomacromolecules to an extent, it lacks the monodispersity and structural purity present in nature. Here we demonstrate that side-chain heterogeneity within graft polymers significantly influences hydration and the occurrence of hydrophobic interactions in the subsequently formed brushes and consequently impacts fundamental interfacial properties. This is demonstrated for the case of poly(methacrylate)s (PMAs) presenting oligomeric side chains of different length ( n ) and dispersity. A precise tuning of brush structure was achieved by first synthesizing oligo(2-ethyl-2-oxazoline) methacrylates (OEOXMAs) by cationic ring-opening polymerization (CROP), subsequently purifying them into discrete macromonomers with distinct values of n by column chromatography, and finally obtaining poly[oligo(2-ethyl-2-oxazoline) methacrylate]s (POEOXMAs) by reversible addition-fragmentation chain-transfer (RAFT) polymerization. Assembly of POEOXMA on Au surfaces yielded graft polymer brushes with different side-chain dispersities and lengths, whose properties were thoroughly investigated by a combination of variable angle spectroscopic ellipsometry (VASE), quartz crystal microbalance with dissipation (QCMD), and atomic force microscopy (AFM) methods. Side-chain dispersity, or dispersity within brushes, leads to assemblies that are more hydrated, less adhesive, and more lubricious and biopassive compared to analogous films obtained from graft polymers characterized by a homogeneous structure.

Poly(ethyl ethylene phosphonate)-based methacrylic copolymers containing polysiloxane methacrylate (SiMA) co-units are proposed as surface-active additives as alternative solutions to the more investigated polyzwitterionic and polyethylene glycol counterparts for the fabrication of novel PDMS-based coatings for marine antifouling applications. In particular, the same hydrophobic SiMA macromonomer was copolymerized with a methacrylate carrying a poly(ethyl ethylene phosphonate) (PEtEPMA), a phosphorylcholine (MPC), and a poly(ethylene glycol) (PEGMA) side chain to obtain non-water soluble copolymers with similar mole content of the different hydrophilic units. The hydrolysis of poly(ethyl ethylene phosphonate)-based polymers was also studied in conditions similar to those of the marine environment to investigate their potential as erodible films. Copolymers of the three classes were blended into a condensation cure PDMS matrix in two different loadings (10 and 20 wt%) to prepare the top-coat of three-layer films to be subjected to wettability analysis and bioassays with marine model organisms. Water contact angle measurements showed that all of the films underwent surface reconstruction upon prolonged immersion in water, becoming much more hydrophilic. Interestingly, the extent of surface modification appeared to be affected by the type of hydrophilic units, showing a tendency to increase according to the order PEGMA < MPC < PEtEPMA. Biological tests showed that Ficopomatus enigmaticus release was maximized on the most hydrophilic film containing 10 wt% of the PEtEP-based copolymer. Moreover, coatings with a 10 wt% loading of the copolymer performed better than those containing 20 wt% for the removal of both Ficopomatus and Navicula , independent from the copolymer nature.