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Macromol, Volume 2, Issue 4 (December 2022) – 7 articles

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Review
A Review of Xyloglucan: Self-Aggregation, Hydrogel Formation, Mucoadhesion and Uses in Medical Devices
Macromol 2022, 2(4), 562-590; https://doi.org/10.3390/macromol2040037 - 06 Dec 2022
Viewed by 145
Abstract
The present paper reviews the self-aggregation, gel-forming and adsorption properties of xyloglucan (XG), and its main applications as a medical device for wound dressings, mucosal protection and ocular lubrication, as well as its uses as an excipient. XG is a branched polysaccharide composed [...] Read more.
The present paper reviews the self-aggregation, gel-forming and adsorption properties of xyloglucan (XG), and its main applications as a medical device for wound dressings, mucosal protection and ocular lubrication, as well as its uses as an excipient. XG is a branched polysaccharide composed of a central backbone of D-glucose units linked by β(1→4)-glycosidic bonds, decorated with D-xylose units through α(1→6) glycosidic bonds, and with some D-galactose units anchored to these D-xylose units via β(1→2) bonds. XG forms self-aggregates with a hierarchically ordered morphology in aqueous solutions, leading to the formation of nanofibers. Consequently, XG is a hydrogel-forming polymer able to retain large amounts of water. Inside the human digestive tract, XG is enzymatically degalactosylated, but the backbone with xylose side chains remains stable until excretion. Degalactosylated XG undergoes a fully reversible sol–gel transition, forming hydrogels between upper and lower critical temperatures. XG adsorbs on intestinal mucosa and creates a diffusion barrier that reduces permeability and also prevents bacterial infections by reducing their infiltration. Therefore, orally administered XG is considered a mucosa protectant. Full article
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Article
Novel Method of Carbon Precursor Masking to Generate Controlled Perforations in a Carbon Film
Macromol 2022, 2(4), 554-561; https://doi.org/10.3390/macromol2040036 - 05 Dec 2022
Viewed by 302
Abstract
A patterned carbon film was produced from Linear Low-Density Polyethylene (LLDPE) by the implementation of a novel method named Chemical Masking Perforation (CMP). The following paper describes this procedure, starting with the sulfonation of the precursor polymer LLDPE with Chlorosulphonic acid to stabilize [...] Read more.
A patterned carbon film was produced from Linear Low-Density Polyethylene (LLDPE) by the implementation of a novel method named Chemical Masking Perforation (CMP). The following paper describes this procedure, starting with the sulfonation of the precursor polymer LLDPE with Chlorosulphonic acid to stabilize the material, followed by Fourier-transform infrared spectroscopy (FTIR) evaluation to compare the atomic bonds from the stabilized film as well as from the masked sections of the film. To finalize, the cross-linked film was carbonized in an oven at 950 °C. The outcome of this process was a carbon film with a thickness similar to a carbon fiber diameter of 8 µm with controllable size and distribution. Full article
(This article belongs to the Special Issue Functionalization of Polymers for Advanced Applications)
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Article
Fabrication and Characterization of Free-Standing and Flexible Polyaniline Membranes: Role of Graphene Nanoscrolls
Macromol 2022, 2(4), 543-553; https://doi.org/10.3390/macromol2040035 - 21 Nov 2022
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Abstract
Wearable technologies can contribute to the early and accurate detection of chronic diseases which can be achieved by the integration of biosensors into wearable technologies. However, the challenges associated with the performance of current electrode materials—i.e., flexibility, conductivity, and mechanical stability, made from [...] Read more.
Wearable technologies can contribute to the early and accurate detection of chronic diseases which can be achieved by the integration of biosensors into wearable technologies. However, the challenges associated with the performance of current electrode materials—i.e., flexibility, conductivity, and mechanical stability, made from conducting polymers are preventing their widespread usage. Herein, we report a freestanding and flexible electrode synthesized from polyaniline (PANI) and graphene nanoscrolls (GNS). The PANI-GNS nanohybrid membranes were synthesized via chemical oxidative polymerization and characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), nanoindentation (NI), and four-point probe techniques. FTIR results showed an increase in conjugation length of the PANI after the addition of GNS into the mixture which can be indicative of an enhancement of electrical properties. Nanoindentation studies showed an elastic modulus and hardness of 2.6 GPa and 0.17 GPa, respectively, for PANI-GNS-5 nanocomposite, compared to 1.9 GPa and 0.08 GPa, for pure PANI. This was later confirmed by the four-point probe technique as the addition of GNS increased the conductivity of electrodes up to 9 S/cm at a 5% weight ratio. Moreover, SEM results of the PANI-GNS showed an open porous morphology of the polymer matrix in comparison with pure PANI samples which would readily translate into higher amounts of enzyme immobilization on the surface. Full article
(This article belongs to the Special Issue Functionalization of Polymers for Advanced Applications)
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Article
Characterization of a Biocomposite of Electrospun PVDF Membranes with Embedded BaTiO3 Micro- and Nanoparticles
Macromol 2022, 2(4), 531-542; https://doi.org/10.3390/macromol2040034 - 17 Nov 2022
Viewed by 333
Abstract
Damage to bone tissue is a common health issue that tends to increase in severity with age and other underlying conditions. To take advantage of the piezoelectric effect on bone remodulation, piezoelectric materials can be used to fill patients bone defects. Polyvinylidene fluoride [...] Read more.
Damage to bone tissue is a common health issue that tends to increase in severity with age and other underlying conditions. To take advantage of the piezoelectric effect on bone remodulation, piezoelectric materials can be used to fill patients bone defects. Polyvinylidene fluoride (PVDF) and barium titanate (BaTiO3) are both well-known polymeric and ceramic biomaterials, respectively, as well as piezoelectric at room temperature. To mimic the extracellular matrix, PVDF membranes were produced by electrospinning onto a rotating drum to promote the alignment of fibers and micro- and nano-sized tetragonal BaTiO3 particles were embedded into these membranes to try to enhance the piezoelectric response and, therefore, bioactivity. After defining the best deposition parameters to produce pure PVDF membranes, the same parameters were carried over for the embedded membranes and both were characterized, revealing that the proposed method for obtaining β-phase PVDF (the polymer phase with highest piezoelectric coefficient) through electrospinning is viable, producing fibers with coherent diameters and alignment. The presence of barium titanate conferred bioactivity to the membranes and caused a decrease in fibers’ diameter and in superficial charge density. Full article
(This article belongs to the Special Issue Functionalization of Polymers for Advanced Applications)
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Article
Enzymatic Degradation of Fiber-Reinforced PLA Composite Material
Macromol 2022, 2(4), 522-530; https://doi.org/10.3390/macromol2040033 - 27 Oct 2022
Viewed by 424
Abstract
Application of thermoplastic fiber-reinforced lightweight composite materials provides a wide range of advantages that are of particular importance for the mobility sector. UD tapes composed of unidirectionally (UD) oriented inorganic fibers embedded in a thermoplastic matrix represent light-weight materials with high tensile strength. [...] Read more.
Application of thermoplastic fiber-reinforced lightweight composite materials provides a wide range of advantages that are of particular importance for the mobility sector. UD tapes composed of unidirectionally (UD) oriented inorganic fibers embedded in a thermoplastic matrix represent light-weight materials with high tensile strength. This publication addresses recycling aspects of novel UD tape made of a combination of basalt fibers and different PLA (polylactic acid) formulations. The kinetics of enzyme-based separation of polymer from the fiber were investigated. Different types of UD tapes with a thickness of 270–290 µm reinforced with basalt fiber weight ratios ranging between 51 and 63% were incubated at 37 °C in buffer solution (pH 7.4) containing proteinase K. The influence of enzyme concentration, tape weight per incubation tube, proteinase K activators, and tape types on the rate of enzymatic decomposition was investigated. Enzyme activity was measured by analyzing lactate concentration with lactate dehydrogenase and by measuring weight loss of the composite material. The rate of lactate release increased in the first 30 min of incubation and remained stable for at least 90 min. Weight loss of 4% within 4 h was achieved for a tape with 56% (w/w) fiber content. For a sample with a surface area of 3 cm2 in a buffer volume of 10 mL, the rate of lactate release as a function of enzyme concentration reached saturation at 300 µg enzyme/mL. With this enzyme concentration, the rate of lactate release increased in a linear manner for tape surface areas between 1 and 5 cm2. Four tapes with different PLA types were treated with the enzyme for 17 h. Weight loss ranged between 7 and 24%. Urea at a concentration of 0.5% (w/v) increased lactate release by a factor of 9. Pretreatment of tapes in alkaline medium before enzymatic degradation increased weight loss to 14% compared to 5% without pretreatment. It is concluded that enzymatic PLA hydrolysis from UD tapes is a promising technology for the release of basalt fibers after alkaline pretreatment or for the final cleaning of basalt fibers. Full article
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Article
Mechanical Response of Reactive Extruded Biocomposites Based on Recycled Poly(lactic Acid) (R-PLA)/Recycled Polycarbonate (R-PC) and Cellulosic Fibers with Different Aspect Ratios
Macromol 2022, 2(4), 509-521; https://doi.org/10.3390/macromol2040032 - 26 Oct 2022
Viewed by 327
Abstract
Coupling recycling processes with increased use of bio-derived and environmentally friendly materials, with the aim of approaching (or overcoming) the mechanical properties of petroleum-derived plastics, is a path that research is pursuing in small but important steps. It is in this stream that [...] Read more.
Coupling recycling processes with increased use of bio-derived and environmentally friendly materials, with the aim of approaching (or overcoming) the mechanical properties of petroleum-derived plastics, is a path that research is pursuing in small but important steps. It is in this stream that this paper wants to fit in developing recycled poly(lactic acid) (R-PLA)/recycled polycarbonate (R-PC) blends obtained from thermoforming processing scraps and reinforcing them with cellulosic-derived fibers, having three different aspect ratios. The aim is to understand the mechanical properties of “second life” materials, their adherence to some micromechanical predictive models and the reinforcement capacity of these natural fibers in relation to their dimensions. Moreover, a compatibilizing system, based on Triacetin (TA) and Tetrabutylammonium Tetraphenylborate (TBATPB), has been added during the extrusion to investigate if a reactive process among R-PLA/R-PC and cellulosic fibers can be achieved. Full article
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Article
Copolymerization of Ethylene and Methyl Acrylate by Dibenzocycloheptyl-Substituted Aryliminopyridyl Ni(II) Catalysts
Macromol 2022, 2(4), 500-508; https://doi.org/10.3390/macromol2040031 - 23 Oct 2022
Cited by 1 | Viewed by 391
Abstract
Copolymerization of ethylene with polar vinyl monomers to yield functionalized and possibly easier recyclable polyolefins is challenging and it is currently being pursued mainly using expensive Pd-based catalysts. Herein, the copolymerization of ethylene and methyl acrylate (MA) is achieved by the dibenzocycloheptyl-substituted aryliminopyridyl [...] Read more.
Copolymerization of ethylene with polar vinyl monomers to yield functionalized and possibly easier recyclable polyolefins is challenging and it is currently being pursued mainly using expensive Pd-based catalysts. Herein, the copolymerization of ethylene and methyl acrylate (MA) is achieved by the dibenzocycloheptyl-substituted aryliminopyridyl Ni(II) complexes, affording copolymers with selectively in-chain incorporated MA units as well as both in-chain and end-of-chain inserted MA units depending on the catalyst structure and the reaction conditions Full article
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