Chitosan/P3HT biohybrid films as polymer matrices for the in-situ synthesis of CdSe quantum dots. Experimental and theoretical studies

Biohybrid nanocomposite films were obtained through a simple two-step methodology. Films of chitosan/poly(3-hexylthiophene) (CS/P3HT) were used as polymer matrices for the in-situ synthesis and stabilization of CdSe quantum dots. The biohybrid materials were characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), Raman spectroscopy, UV–visible spectroscopy, thermogravimetric analysis (TGA), field emission scanning electron microscope (FESEM), high-resolution transmission electron microscopy (HRTEM), and photoluminescence spectroscopy (PL). The effects of the P3HT composition on the properties of the QDs in the films were analyzed. The results confirmed that CS/P3HT films provided an adequately confining matrix for the growth of CdSe QDs with a fairly uniform size and revealed that the interactions between the CdSe nanoparticles and the CS/P3HT matrix mainly involved the  OH and  NH₂ groups. The optical band gaps of the biohybrid nanocomposite films were estimated. The results of photoluminescence revealed that a charge transfer phenomenon occurred in the polymer system. Finally, theoretical analyses suggest that the CdSe QDs would be preferentially located onto the chitosan domains.     

Imparting antimicrobial properties to natural rubber latex foam via green synthesized silver nanoparticles

The green synthesis of silver nanoparticles (AgNPs) in centrifuged natural rubber latex (NRL) by in situ reduction of silver nitrate by NRL is described. The synthesis of AgNP within NRL was successfully carried out without the addition of any reducing agent or stabilizers. The modified AgNP incorporated with centrifuged NRL (GAgNP_NRL) was used to make NRL foam (NRLF) by the Dunlop production method. An ultraviolet–visible (UV‐Vis) spectrophotometer analysis, Zeta potential analysis data and transmission electron micrograph analysis proved that the modified centrifuged NRL consisted of stable nanometer‐sized silver particles. A scanning electron microscopic (SEM)/energy‐dispersive X‐ray spectroscopy (EDX) analysis and UV‐Vis analysis of a latex film made out of the modified GAgNP_NRL compound showed nano‐sized silver particles inside the rubber matrix. The final product of the NRLF (GAgNP_NRLF) made out of the GAgNP_NRL compound was tested for antimicrobial properties against gram‐negative Escherichia coli, gram‐positive Staphylococcus aureus and Staphylococcus epidermidis. The resultant GAgNP_NRLF strongly inhibited the bacteria. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40155.     

Increasing the elongation at break of polyhydroxybutyrate biopolymer: Effect of cellulose nanowhiskers on mechanical and thermal properties

Bionanocomposites based on polyhydroxybutyrate (PHB) and cellulose nanowhiskers (CNWs) were prepared by dispersing CNWs in poly(ethylene glycol) (PEG) plasticizer subsequently incorporating the CNWs/PEG suspensions in the matrix. The thermal properties of the nanocomposites indicate an enlargement in the processing window in comparison to the neat PHB. The nanocomposites showed a remarkable increase in the strain level (50 times related to the neat PHB), without a significant loss of the tensile strength with the incorporation of small concentrations of CNWs in the final nanocomposite (up to 0.45 wt %). This behavior was explained in terms of a considerable chain orientation promoted by the presence of CNWs in the same direction of the applied load, which activated shear flow of the polymer matrix. The results described here can be explored to extend the applications of this biopolymer. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis of poly(butyl acrylate)—laponite nanocomposite nanoparticles for improving the impact strength of poly(lactic acid)

This work aims at preparing and characterizing poly(butyl acrylate) (PBA)—laponite (LRD) nanocomposite nanoparticles and nanocomposite core (PBA‐LRD)‐shell poly(methyl methacrylate) (PMMA) nanoparticles, on the one hand, and the morphology and properties of poly(lactic acid) (PLA)‐based blends containing PBA‐LRD nanocomposite nanoparticles or (PBA‐LRD)/PMMA core–shell nanoparticles as the dispersed phase, on the other hand. The PBA and (PBA‐LRD)/PMMA nanoparticles were synthesized by miniemulsion or emulsion polymerization using LRD platelets modified by 3‐methacryloxypropyltrimethoxysilane (MPTMS). The grafting of MPTMS onto the LRD surfaces was characterized qualitatively using FTIR and quantitatively using thermogravimetric analysis (TGA). The amounts of LRD in the PBA‐LRD nanocomposites were characterized by TGA. The PBA/PMMA core–shell particles were analyzed by ¹H‐NMR. Their morphology was confirmed by SEM and TEM. Mechanical properties of (PBA‐LRD)/PLA blends and (PBA‐LRD)/PMMA/PLA ones were tested and compared with those of the pure PLA, showing that core–shell particles allowed increasing impact strength of the PLA while minimizing loss in Young modulus and tensile strength. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Poly(butylene succinate)/layered double hydroxide bionanocomposites: Relationships between chemical structure of LDH anion,delamination strategy,and final properties

A series of poly(butylene succinate) (PBS) containing organo‐modified layered double hydroxide (LDH) are prepared by melt compounding and by in situ polymerization of succinic ester and 1,4‐butanediol. Various LDHs intercalated with renewable organic anions are used. More specifically, lauryl sulfate, stearate, succinate, adipate, sebacate, citrate, and ricinoleate ions are used as LDHs organo‐modifiers. The thermal, rheological, and dynamic mechanical properties of the samples are investigated. The results reveal a general mechanical reinforcement imparted by the clays. Significant changes are observed for the in situ polymerized nanocomposites, especially for LDH stearate which improves the properties of PBS nanostructure, whereas very few differences are observed for the other samples. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1931–1940, 2013     

Combined effect of cassava starch nanoparticles and protein isolate in properties of starch-based nanocomposite films

This study aimed to evaluate the effects of incorporation of cowpea protein isolate and cassava starch nanoparticles obtained by ultrasound on the properties of cassava starch:glycerol films. The cowpea bean protein isolate was successfully obtained with 72.5% of protein and solubility about 90%. The cassava starch nanoparticles yielded 97.85%. Increasing protein isolate concentration in starch:glycerol films resulted in a progressive reduction of water vapor permeability up to 27.0%. The cassava starch nanoparticles added films presented expressive increments in tensile strength (283.83%) as well as modulus of elasticity (204.31%), accompanied by decreasing in elongation at break (24.28%). The thermal stabilities of cassava starch films were affected by the addition of both protein isolate and cassava starch nanoparticles. The cassava starch nanoparticles obtained by ultrasound ensured the maintenance of film properties, optimizing the production time, with a higher yield, and without the need for chemical reagents. Thus, it could be useful for substitution of those obtained by acid hydrolysis. Therefore, giving rise to a trend of production of nanocomposite films suitable for reinforced packaging applications.     

Fabrication of superhydrophobic polylactide films with ultraviolet-shielding properties

ZnO is a useful material with stable physical and chemical properties for introducing surface roughness and UV-blocking properties. However, to inhibit ZnO particles’ photocatalytic degradation of peripheral organic materials, we conducted layer-by-layer (LbL) deposition with poly(sodium 4-styrenesulfonate) and poly(diallyl dimethyl ammonium chloride) to fabricate ZnO particles with an SiO₂ shell with tetraethyl orthosilicate. Polylactide (PLA) films were prepared by compression molding and treated with a weak alkali solution for 0.5, 1.0, 1.5, and 2.0 h to induce hydroxyl and carboxyl groups. The LbL deposition of polyelectrolytes on the PLA film was performed to induce electrical interactions between the PLA films and ZnO composite particles. ZnO composite particles were deposited onto the surface of the PLA films with dip coating, and a stable superhydrophobic surface was developed after hexadecyl trimethoxysilane treatment via a reduction in the surface energy. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47760.     

A novel polymer composite with a small optical band gap: New approaches for photonics and optoelectronics

In this article, a novel approach is presented for the preparation of small band‐gap polymer composites. The intensity of the surface plasmon resonance (SPR) peak increased from 0.64 to 3.2 for the chitosan–silver nitrate sample containing 1 wt % titanium dioxide (TiO₂). In the cases of 3 and 5 wt % added TiO₂ particles, the SPR peak disappeared. A wide shift of the absorption coefficient from 4.36 to 0.93 eV was observed. The smallest optical band gap of about 0.98 eV was achieved for the sample containing 3 wt % TiO₂ filler. The wide shift in the optical band gap was interpreted on the bases of the formation of metal‐induced gap states between the metallic silver particles and the TiO₂ structure. A novel approach was achieved that was an alternative method to Tauc's semi‐empirical model for band‐gap estimation. The optical dielectric loss parameter for the band‐gap study was easily calculated and analyzed, whereas it unfolded a deep knowledge from the physics point of view. The established quantum mechanical expression revealed a strong relationship between the energy band gap and the optical dielectric loss parameter. The scanning electron microscopy results show the leakage of white aggregated silver particles and distinguishable intense peaks of metallic silver particles between 3 and 3.3 keV appearing in the energy‐dispersive X‐ray spectrum. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44847.     

Elaboration and properties of renewable polyurethanes based on natural rubber and biodegradable poly(butylene succinate) soft segments

Natural rubber (NR) is a renewable bio‐based polymer, while poly(butylene succinate) (PBS) belongs to the family of biodegradable renewable polymers. In this article, novel polyurethanes (PUs) were prepared using hydroxyl telechelic natural rubber (HTNR) and hydroxyl telechelic poly(butylene succinate) (HTPBS) as soft segments, and using toluene‐2,4‐diisocyanate (TDI) and 1,4‐butanediol (BDO) as hard segment. HTPBS oligomers of = 2000 and 3500 g mol^?1 were synthesized by bulk polycondensation of succinic acid (SA) with BDO. The polyurethane materials were obtained by casting process after solvent evaporation. The influence of the hard segment content and the molecular weight of HTPBS on the materials’ thermo‐mechanical properties were investigated by means of tensile testing, DSC, TGA, and DMTA. The obtained polyurethanes were amorphous with phase separations between hard and soft segments as well as between HTNR and HTPBS segments, and they exhibited good physical properties. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42943.     

Prodegradant effect of titanium dioxide nanoparticulates on polypropylene–polyhydroxybutyrate blends

Polymers are gradually replacing conventional materials in various sectors of the economy because of their low cost and broad functionality. However, the high stability of polymers under most environmental conditions can lead to their accumulation in the form of waste. Polyhydroxybutyrate (PHB) is an alternative because of its biodegradability, but it is usually expensive and brittle. These aspects can be improved through the formation of blends, such as with polypropylene (PP). The objective of this study was to investigate the possibility of using titanium dioxide (TiO₂) nanoparticles as a prodegradant agent in the PP–PHB–TiO₂ system through the evaluation of the effects of these nanoparticles under UV light on the structure and properties of the materials. Samples were produced through extrusion and injection molding and were characterized by their mechanical and thermal properties and structural analyses. The results show that the TiO₂ nanoparticles were able to act as a prodegradant agent for the PP–PHB blend; they also successfully improved some of the mechanical and dynamic mechanical properties of the blend. However, a TiO₂ nanoparticle content higher than 7.5 wt % was not able to extend the photodegradation process further, possibly as a consequence of the agglomeration of nanoparticles during the processing of these more concentrated blends. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46636.     

Self‐aggregated nanoparticles of N‐dodecyl,N′‐glycidyl(chitosan) as pH‐responsive drug delivery systems for quercetin

In this study, pH‐responsive amphiphilic chitosan (CS) nanoparticles were used to encapsulate quercetin (QCT) for sustained release in cancer therapy. The novel CS derivatives were obtained by synthesis with 2,3‐epoxy‐1‐propanol, also known as glycidol, followed by acylation with dodecyl aldehyde. Characterization was performed by spectroscopic, viscosimetric, and size‐determination methods. Critical aggregation concentration, morphology, entrapment efficiency, drug release profile, cytotoxicity, and hemocompatibility studies were also carried out. The average size distribution of the self‐assembling nanoparticles measured by dynamic light scattering ranged from 140 to 300 nm. In vitro QCT release and Korsmeyer–Peppas model indicated that pH had a major role in drug release. Cytotoxicity assessments indicated that the nanoparticles were non‐cytotoxic. 3‐(4,5‐Dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide assay further revealed that QCT‐loaded nanoparticles could inhibit MCF‐7 cell growth. In vitro erythrocyte‐induced hemolysis indicated the good hemocompatibility of the nanoparticles. These results suggest that the synthesized copolymers might be potential carriers for hydrophobic drugs in cancer therapy. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45678.     

Impact of thermal processing or solvent casting upon crystallization of PLA nanocellulose and/or nanoclay composites

Here, we present how processing (solvent casting or isothermal crystallization) impacts crystallinity of poly(lactic acid) (PLA) and its nanocomposites (PLA/1 wt % cellulose nanofibers (CNFs), PLA/1 wt % nanoclay (C30B) or PLA/1 wt % CNF/1 wt % C30B. Polarized optical microscopy demonstrated a heterogeneous nucleation process during isothermal crystallization leading to smaller homogeneously distributed spherulites. With solvent casting, no effect on morphology was observed with respect to the nanoparticles, but an increased spherulite size was observed at higher temperatures. This fact raises significant concerns regarding the suitability of solvent casting as a lab-scale procedure to investigate materials. Additionally, combining the reinforcing agents, CNF, and C30B, did not increase nucleation rate, in contrast with the general tendency, where the incorporation of both particles led to improved properties (e.g., thermomechanical and barrier properties). However, a combination of C30B and CNF did lead to an overall increase in the rigid amorphous fraction and a reduced mobile amorphous fraction. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47486.     

Microbial cellulose as a support for photocatalytic oxidation of toluene using TiO2 nanoparticles

The aim of this study was to investigate the feasibility of toluene degradation using impregnated microbial cellulose (MC) with titanium dioxide (TiO₂) nanoparticles (MC/TiO₂). The effects of the initial toluene concentration and ultraviolet (UV) source on the degradation efficiency of toluene have been evaluated. The experimental results showed that the rate of toluene degradation decreased with an increasing of the inlet toluene concentration. After 40 min reaction time, the decomposition rate (%) of toluene decreased from 72.3% to 36.02% for experiments conducted at 100 and 500 ppm, respectively. The degradation efficiency of toluene decreased with application of UVA source instead of UVC source. The toluene degradation efficiency (%) reached to 87.79% and 76.87% for UVC and UVA irradiation, respectively. At initial toluene concentration of 100 mg/L, toluene degradation efficiency for photocatalysis and photolysis processes were 70.2% and 10.65%, respectively; indicating that the photocatalytic degradation efficiency is significantly higher than that of photolytic degradation efficiency. Furthermore, photocatalytic degradation kinetics of toluene was studied and the rates of degradation were found to conform to pseudo‐second‐order kinetic. As shown in the present study, impregnation of TiO₂ nanoparticles on MC/TiO₂ significantly increases toluene removal for short exposure time. It can be concluded that the MC acted as a local toluene concentrator by adsorbing pollutants from the air stream, and thereby diffusing them to the TiO₂ nanoparticles for photodegradation. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43051.     

Comparison of thermoset soy protein resin toughening by natural rubber and epoxidized natural rubber

Fully bio‐based soy protein isolate (SPI) resins were toughened using natural rubber (NR) and epoxidized natural rubber (ENR). Resin compositions containing up to 30 wt % NR or ENR were prepared and characterized for their physical, chemical and mechanical properties. Crosslinking between SPI and ENR was confirmed using ¹H‐NMR and ATR‐FTIR. All SPI/NR resins exhibited two distinctive drops in their modulus at glass transition temperature (T_g ) and degradation temperature (T_d ) at around ?50 and 215 °C, corresponding to major segmental motions of NR and SPI, respectively. SPI/ENR resins showed similar T_g and T_d transitions at slightly higher temperatures. For SPI/ENR specimens the increase in ENR content from 0 to 30 wt % showed major increase in T_g from ?23 to 13 °C as a result of crosslinking between SPI and ENR. The increase in ENR content from 0 to 30 wt % increased the fracture toughness from 0.13 to 1.02 MPa with minimum loss of tensile properties. The results indicated that ENR was not only more effective in toughening SPI than NR but the tensile properties of SPI/ENR were also significantly higher than the corresponding compositions of SPI/NR. SPI/ENR green resin with higher toughness could be used as fully biodegradable thermoset resin in many applications including green composites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44665.     

Preparation of high-performance deproteinized natural rubber/chitosan composite films via a green and sulfur-free method

To solve the environment and health issues arose from the sulfur vulcanization, a facile and completely eco-friendly method of latex-assembly and in situ cross-linking is developed to prepare fully bio-based and high-performance rubber films. The films are featured by a “reinforced concrete” structure composed of dynamically cross-linked chitosan framework and unvulcanized deproteinized natural rubber (DPNR) matrix. The self-assembly of DPNR latex particles and chitosan, as well as the in situ cross-linking of chitosan in the film forming process are confirmed by transmission electron microscope and dynamic light scattering. As green rubbers without vulcanization, the as-designed composite films possess excellent mechanic properties comparable to those of the sulfur vulcanized DPNR film, whose tensile strength and toughness reach 15.2 MPa and 77.6 MJ m⁻³ respectively. Moreover, the films exhibited appropriate permeability to moisture and achievable reprocessing, which have potential applications in wearable devices.     

PLA/sepiolite and PLA/calcium carbonate nanocomposites: A comparison study

Polylactic acid (PLA)‐based nanocomposites comprising two different types of nanofillers, i.e. sepiolite (SEP) and nano calcium carbonate (NCC), were prepared by internal mixing and injection molding. Because of the different aspect ratio, surface area, and surface property of the nanofillers, their effects on the morphological, mechanical, dynamic mechanical, rheological, and thermal properties of the nanocomposites were shown to be very different. NCC demonstrated more uniform particle dispersion and matrix compatibility than did SEP because of the former's surface treatment, thus leading to higher strength and strain‐at‐failure of PLA/NCC composites. On the other hand, larger aspect ratio and surface area of SEP caused higher melt viscosity, stronger shear thinning, and better thermal resistance of PLA/SEP composites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Photoactivity of Poly(lactic acid) nanocomposites modulated by TiO2 nanofillers

Photoactivity of poly(lactic acid) (PLA) nanocomposites is of great interest for rational design of products for either short‐term/single‐use or long‐term/durable applications. We prepared PLA/TiO₂ nanocomposite films through a solution mixing/film casting method. Results showed that photodegradability/photostability of PLA could be well modulated by selecting appropriate TiO₂ nanofillers. TiO₂ nanoparticles and nanowires were characterized using X‐ray diffraction, UV–Vis–NIR spectrophotometer, and scanning electron microscopy. Changes in color, weight, structure, thermal stability, and phase transitions of PLA and nanocomposite films before and after UV irradiation were evaluated to study photoactivity characteristics. Pure PLA exhibited moderate photodegradability, but the photodegradability and photostability of PLA nanocomposites (PNA) were significantly enhanced by NanoActive (NA) TiO₂ nanoparticles and A type TiO₂ nanowires, respectively. Pure PLA had a weight loss of 27% after 38 days of UV irradiation. The weight loss of photodegradable (PD) PNA (PNA = PLA with 1% NA TiO₂) reached 38%, whereas that of photostable (PS) nanocomposites (P3AW) (P3AW = PLA with 3% A type TiO₂ nanowire) was only 5%. PD PLA exhibited characteristic peaks of carboxylic acid OH stretching and C?C double bond after UV irradiation in Fourier‐transform infrared spectra, whereas spectra of PS PLA remained almost the same. Thermal decomposition temperatures, glass transition temperatures, and melting temperatures of PD PLAs decreased dramatically after UV irradiation, but no obvious changes were observed for those of PS PLAs. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40241.     

Morphology and antibacterial properties of natural rubber composites based on biosynthesized nanosilver

The objective of this work is to improve the properties of natural rubber composites (NRC) that were frequently used in medical and health supplies, using nanosilver additions. Silver nanocolloids were biosynthesized with an aqueous medium of aloe leaf extract (ALE) as capping agent, and then were filled in natural rubber matrix to prepare nanosilver‐based NRC. UV–vis spectrophotometer, X‐ray diffraction, and transmission electron microscopic analyses proved that the particle size of resultant silver was about 20 nm. The antibacterial activities against Staphylococcus aureus and Escherichia coli bacteria of NRC were dependable on the silver nanoparticles content and the treating methods on ALE, which was used in synthesizing silver nanocolloids. The morphology and thermal stability effect of nanosilver on NRC were determined with scanning electron microscopic and thermogravimetric analysis, respectively. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40746.     

A comparative study for the behavior of 3D-printed and compression molded PLA/POSS nanocomposites

Because of the biocompatible and nontoxic character of both PLA (polylactide) and POSS (Polyhedral Oligomeric Silsesquioxane) nanoparticles, recently being a significant alternative for biomedical parts; the main purpose of this study was to investigate performance of the 3D-printed PLA/POSS nanocomposites with respect to the compression molded PLA/POSS specimens. Due to the higher uniformity and higher homogeneity in the distribution of POSS nanoparticles in each PLA matrix layer, mechanical tests (tensile, flexural, and toughness) revealed that the improvements in the strength, elastic modulus and fracture toughness values of the 3D-printed specimens were much higher compared to their compression molded counterparts, the benefits starting from 13% increasing up to 78%. It was also observed that there was almost no deterioration in the physical structure and mechanical properties of the 3D-printed specimens, even after keeping them 120 days at 37°C in a physiological solution prepared by using the standard PBS (phosphate buffered saline) tablet.     

Amorphous poly(3‐hydroxybutyrate) nanoparticles prepared with recombinant phasins and PHB depolymerase

Phasin protein (PhaP) is known to anchor into the matrix of phospholipid surrounding polyhydroxyalkanoic acid (PHA) inclusion bodies formed in bacterial cells and regulate the size of the granules, as well as the number of PHA granules. To investigate the effect of phasin on the formation of artificial poly(3‐hydroxybutyrate) (P(3HB)) granules in vitro, (His)₆‐tagged or GST‐fusion recombinant phasin was prepared and utilized for the artificial granule preparation. In addition, a P(3HB) depolymerase was coloaded with the recombinant phasin to prepare self‐degradable phasin‐coated P(3HB) granules. A water/chloroform two‐phase emulsion technique was used, in which the emulsification was carried out by sonication, and the chloroform in the emulsion was removed by stirring‐aided evaporation at room temperature or 65°C. Slower chloroform removal at room temperature produced better spherically shaped P(3HB) nanogranules, which were uniformly sized (～100 to 200 nm in diameter). The self‐degradability of P(3HB) depolymerase‐loaded P(3HB) nanogranules was investigated. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41074.