Search

Polyimide (PI) foams have been developed for decades and widely used as thermal insulation materials. However, the limited mechanical and thermal properties continually being a serious problem that restrict their further applications. In this study, a series of rigid PI foams with excellent mechanical and thermal performance were fabricated by the reaction of benzophenone-3,3',4,4'-tetracarboxylic dianhydride (BTDA) with two diamines of 2–(4-aminophenyl)-5-aminobenzimidazole (BIA) and 4,4'-diaminodiphenyl ether (ODA) with various molar ratios, and the cis-5-norbornene-endo-2,3-dicarbox-ylic acid (NA) was introduced as end-capping and foaming agent. The results demonstrate that the foaming degree decreases with increasing the BIA molar ratio in the polymer chains owing to the elevated melt viscosity of precursor. Furthermore, the prepared rigid PI foams exhibit excellent thermal and mechanical properties. When the BIA contend up to 40 mol%, the glass transition temperature ( Tg) and the temperature at 10% of weight loss ( Td 10 %) of PI foam increased ∼80°C and ∼35°C in comparison with the pristine PI-0, respectively. In addition, the compressive strength and modulus at 10% strain of PI-4 reached to 5.48 MPa and 23.8 MPa, respectively. For the above-mentioned advantages, the prepared rigid PI foams are promising candidates as thermal insulation and structure support composite materials in the aerospace and aviation industries.

In this study, we have fabricated poly(acrylamide-co-acrylic acid)–Al3+/poly(vinyl alcohol)/graphene oxide (PAmAA–Al3+/PVA/GO) double network nanocomposite hydrogels by free-radical polymerization and a freeze–thaw cycle in the presence of graphene oxide and aluminum ions. The pH-sensitivity, surface morphology and mechanical properties can be tuned by adjusting the contents of GO, PVA and Al3+. The resulting hydrogels exhibit significant pH-sensitivity and an interconnected pore channel. The PAmAA–Al3+/PVA/GO hydrogels also exhibit high tensile strength, a large elongation at break and high toughness, which is due to the introduction of GO and formation of dynamic reversible bonds. These dynamic reversible bonds formed in the synthesized double network nanocomposite hydrogels could efficiently dissipate energy and recover the three-dimensional network. The combination of nanoparticles, dynamical reversible bonds and the double network structure significantly improves the physicochemical properties of these hydrogels. Finally, subcutaneous implantation of the synthesized nanocomposite hydrogels in mice showed no local inflammatory response, indicating good biocompatibility in vivo. In conclusion, PAmAA–Al3+/PVA/GO double network nanocomposite hydrogels with tunable three-dimensional network structures, mechanical properties, good pH-sensitivity, self-healing ability and biocompatibility are promising biomaterials for tissue engineering.

In this study, two alginate-based hydrogels with good mechanical strength, toughness and resilience were synthesized by hydrophobic interaction and coordination bonding. Sodium alginate/poly(acrylamide) semi-interpenetrating network (NaAlg/PAM semi-IPN) hydrogels were first synthesized through the micelle copolymerization of acrylamide and stearyl methacrylate in the presence of sodium alginate, then calcium alginate/poly(acrylamide) double network (CaAlg/PAM DN) hydrogels were prepared by immersing the as-prepared NaAlg/PAM semi-IPN hydrogels in a CaCl2 solution. FT-IR and XPS results revealed NaAlg/PAM semi-IPN hydrogels and CaAlg/PAM DN hydrogels were successfully synthesized through non-covalent interactions. The tensile strength of CaAlg/PAM DN hydrogels could reach 733.6 kPa, and their compressive strengths at 80% strain are significantly higher than those of the corresponding NaAlg/PAM semi-IPN hydrogels, which is attributed to the alginate network crosslinked by Ca2+. The dual physically crosslinked CaAlg/PAM DN hydrogels can achieve fast self-recovery, and good fatigue resistance, which is mainly assigned to energy dissipation through dynamic reversible non-covalent interactions in both networks. The self-healing ability, swelling behavior and morphology of the synthesized alginate-based hydrogels were also evaluated. This study offers a new avenue to design and construct hydrogels with high mechanical strength, high toughness and fast self-recovery properties, which broadens the current research and application of hydrogels.

In this work, the synthesized PLLA/PCL multi-block copolymers with different compositions were introduced into a stereocomplexed poly(lactide) (sc-PLA) matrix to accelerate the stereocomplexation of PLA enantiomers and improve its inherent brittleness. The PLLA/PCL multi-block copolymers were in different compositions to adjust the molecular weight of the PLLA block. The structure, molecular weight, crystallization behavior, crystal structure and thermal stability of PLLA/PCL multi-block copolymers were investigated. The results indicated that PLLA/PCL multi-block copolymers with controllable structure and composition were successfully synthesized. On this basis, the blends of sc-PLA and PLLA/PCL multi-block copolymers were prepared by solution casting, and characterized. The results revealed that the introduction of PLLA/PCL multi-block copolymers promoted the stereocomplexation of the PLA enantiomers during the melting crystallization process to obtain a complete stereocomplexed material. But the presence of the PCL block leads to a decrease in the melting temperature of the stereocomplex and difficulty in homogeneous nucleation. Compared with sc-PLA, the elongation at break of the blends was significantly improved and their tensile strengths were only slightly reduced. And the thermal stability and mechanical properties of the blends could be adjusted by controlling the content and composition of PCL/PLLA multi-block copolymers. These results revealed that the degree of stereocomplexation and toughness of sc-PLA were improved, which may expand the application fields of PLA-based materials.

Enzyme immobilization technology has a key role in improving the stability of enzyme reaction systems and biocatalyst utilization rates. In this study, polyvinyl alcohol/sodium alginate@Fe

In this study, we investigated the blending of poly(L-lactide) (PLLA) with supramolecular polymers based on poly(D-lactide)–poly(e-caprolactone-co-δ-valerolactone)–poly(D-lactide) (PDLA–PCVL–PDLA) triblock copolymers as an efficient way to modify PLLA. The supramolecular polymers (SMP) were synthesized by the terminal functionalization of the PDLA–PCVL–PDLA copolymers with 2-ureido-4[1H]-pyrimidinone (UPy). The structure, thermal properties and rheological behavior of the synthesized supramolecular polymers were studied; we found that the formation of the UPy dimers expanded the molecular chain of the polymer and the incorporation of the UPy groups suppressed the crystallization of polymers. In addition, the synthesized supramolecular polymers had a low glass transition temperature of about −50 °C, showing the characteristics of elastomers. On this basis, superior properties such as a fast crystallization rate, high melt strength, and toughness of fully bio-based, i.e., PLA-based materials were achieved simultaneously by blending PLLA with the synthesized supramolecular polymers. In the PLLA/SMP blends, PLLA could form a stereocomplex with its enantiomeric PDLA blocks of supramolecular polymers, and the stereocomplex crystals with the cross-linking networks reinforced the melt strength of the PLLA/SMP blends. The influences of the SMP composition and the SMP content in the PLLA matrix on crystallization and mechanical properties were analyzed. The supramolecular polymers SMP0.49 and SMP1.04 showed a reverse effect on the crystallization of PLLA. Tensile tests revealed that the lower content of the synthesized supramolecular polymers could achieve toughening of the PLLA matrix. Therefore, the introduction of supramolecular polymers based on PDLA–PCVL–PDLA is an effective way to control the crystallization, rheology and mechanical properties of PLLA.

Synthetic progestin norethindrone (NET) widely used in oral contraceptives, hormonal therapy and livestock farming has been detected in various aquatic ecosystems. Recent studies have shown that NET can cause thyroid endocrine disruption in amphibians. However, studies are still lacking on thyroid axis of fish. In the present study, we investigated thyroid hormone levels (T3 and T4) and transcriptional patterns of 15 genes of the hypothalamic-pituitary-thyroid axis (HPT axis) in adult zebrafish that were exposed to solvent control and three measured concentrations of NET (7, 84 and 810 ng/L) for 90 days. The results indicated that NET significantly lowered T3 and T4 levels in both female and male zebrafish. Transcriptional expression profiles of some of the HPT-axis related genes were disrupted. Specifically, the expression levels of tshb and pax8 have increased significantly while dio2 and ugt1ab have decreased in females. In male, however, tshb expression levels were increased while ttr, ugt1ab, thra and thrb were decreased. The overall results demonstrate that NET disrupts thyroid endocrine system by interfering at multiple sites along HPT axis in adult zebrafish.

Lightweight and multifunctional PMMA/Fe 3 O 4 @MWCNTs composite foams with density of 0.22–0.38 g/cm 3 were fabricated by supercritical carbon dioxide (ScCO 2 ) foaming process. Benefitting from the existence of microcellular structure and the Fe 3 O 4 @MWCNTs hybrids, the specific Electromagnetic interference shielding effectiveness (EMI SE) of obtained PMMA/Fe 3 O 4 @MWCNTs foams was significantly enhanced. The resulting foams with hybrids loading of 7 wt% displayed excellent specific EMI SE of 50 dB/(g/cm 3 ) over the X-band. Furthermore, the EMI shielding mechanisms of the porous materials were discussed and it suggested that the dominant contribution to EMI SE was absorption. Meanwhile, the high-strength composite foams also exhibited superparamagnetic behavior and low thermal conductivity of 0.080–0.142 W/(m k). In this work, we provide a feasible way to produce lightweight and multifunctional PMMA/Fe 3 O 4 @MWCNTs foams with superior EMI shielding performance to apply in the electronics and aerospace industries.

Alternating poly(lactide)/poly(e-caprolactone) multiblock supramolecular polymers were synthesized by terminal functionalization of PLA-PCL-PLA triblock copolymers with the self-complementary quadruple hydrogen bonding of 2-ureido-4[1 H ]-pyrimidinone (UPy) dimers. The prepared supramolecular copolymers (SMPs) show the properties of thermoplastic elastomers, while the PLA-PCL-PLA is brittle solids, which is attributed to the chain extension induced by UPy units. The effects of the length and stereostructures of PLA blocks, and various initiators on the crystallization and melting behaviors, morphological, mechanical, shape memory and self-healing properties of SMPs were systemically investigated. The incorporation of UPy units obviously depresses the crystallization of polymer chains, but SMPs containing POSS could decline the inhibition of UPy units for crystallization due to the heterogeneous nucleation of POSS. The prepared SMPs have poor ordered micro-phase structure. Mechanical, shape memory and self-healing properties of SMPs could also be easily adjusted by the stereostructures and length of PLA blocks. This would provide potential approaches to control the structure and physical performances of PLA-based materials.

Biodegradable supramolecular polymers (SMPs) are synthesized by the end-functionalization of poly(lactide)-block-poly(δ-valerolactone)-block-poly(lactide) (PLA-PVL-PLA) triblock copolymers with 2-ureido-4[1H]-pyrimidinone (UPy) self-complementary quadruple hydrogen-bonding unites. The end-functionalized PLA-PVL-PLA copolymers exhibit the typical characteristics of thermoplastic elastomers. Thermal, crystallization behavior, crystalline structure and properties of SMPs can be adjusted by changing the length and stereostructure of PLA blocks. The UPy groups retard the crystallization of PLA and PVL blocks, the crystallization of PVL blocks is also depressed by the increasing PLA blocks. Tensile test reveals that the prepared SMPs presents excellent mechanical properties, DMA results indicate that the heat resistance of L-SMPs is better than that of DL-SMPs. Shape memory property of SMPs was also studied, found that recovery ratio of SMPs with PDLLA blocks can reach 100%. The recovery ratio of L-SMPs was depressed as the crystallizable PLLA blocks increase. This study has systemically investigated that effect of the composition, stereostructure, and crystallizability of PLA blocks on the properties of supramolecular polymers, which would provide potential approaches to synthesize the biodegradable supramolecular polymers with tunable properties.

An α-hydroxyphosphonate cyclotriphosphazene compound, hexa-(4-diethylphosphate-hydroxymethyl-phenoxy)-cyclotriphosphazene (HDHPCP), was synthesized and well characterized by FTIR, NMR and elemental analysis. The additive HDHPCP was blended into diglycidyl ether of bisphenol A to prepare flame-retardant epoxy resins (EP). Thermal properties, combustion behaviors and mechanical properties of the epoxy resins cured with 4,4-diaminodiphenyl methane were investigated. The results of thermogravimetric analysis revealed that HDHPCP improved char formation ability of the materials at high temperature and reduced the maximum mass loss rate. Moreover, the limiting oxygen index values of cured EP composites increased from 23.5% for pure EP to 30.7% and reached vertical burning UL-94 V-0 rating for sample with 20 mass% HDHPCP, which demonstrated that the prepared EP thermosets exhibited good flame retardancy. Microscale combustion calorimetry data displayed that peak heat release rate, total heat release and heat release capacity decreased obviously with the increasing content of HDHPCP. Furthermore, the addition of HDHPCP increased impact strengths and decreased the flexural strengths slightly of the flame-retarded EP thermosets.

In this study, a series of porous polyimide films containing benzimidazole units were prepared through a phase separation process. The dibutyl phthalate was selected as porogen. The copolyimides were prepared by the reaction of 3,3′,4,4′-benzophenonetetracarboxylic dianhydride with two diamines of 2-(4-aminophenyl)-5-aminobenzimidazole (BIA) and 4,4′-diaminodiphenyl ether with various molar ratios. The resultant porous polyimide films exhibit optimum cell-size distributions. The effects of BIA on morphology, mechanical, and thermal properties of the porous films were explored. It was found that as the BIA content reached up to 30 mol%, the porous copolyimide film demonstrates remarkable thermal stability and admirable mechanical properties with the glass transition temperature of 294°C, 5% weight loss temperature in argon flow up to 545°C, and a tensile strength of 48 MPa. The incorporation of BIA into the polyimide chains brought the highly rigid structures and strong intermolecular interactions, resulting in the enhancement in the thermal stability and the mechanical properties.

In order to cope with the increasing oil spill accidents and the intentional discharge of oily wastewater, a new oil-adsorbing material with superhydrophobicity and reusability is needed. In this paper, waste plastic was used to fabricate an alveolate polystyrene (PS) foam to reduce secondary pollution. The PS foam was synthesized from a high internal phase Pickering emulsion (HIPPE) technique in a one-step process. The emulsion was stabilized by a co-Pickering system of Span 80 surfactant and SiO2 particles. To explain the super stability of the HIPPE, a novel model of the water-in-oil droplet was promoted. The obtained SiO2@PS foam exhibited a multi-order-porous structure, and displayed superhydrophobicity and superoleophilicity. It can selectively remove various oily contaminants from water with a high adsorption capacity of 20.4–58.1 g g−1 at a fast rate. The oil-adsorbed material can be reused by simple centrifugation, and no more than a 1% decline was obtained in the oil adsorption after 10 cycles. Therefore, the SiO2@PS foam has a great potential application in oily water treatment.

The aim of this study was to assess the long-term effects of synthetic progestin norethindrone (NET) on the growth, reproductive histology, and transcriptional expression profiles of genes associated with the hypothalamic-pituitary-gonadal (HPG) axis and germ cells in adult zebrafish. Adult zebrafish were exposed to 7, 84 and 810 ng/L NET for 90 days. The results showed that exposure to 810 ng/L NET caused a significant decrease in growth of females and males. The ovary weight and GSI was significantly reduced by NET at concentrations of 84 or 810 ng/L, which came along with the delay of ovary maturation in females. However, NET at all treatments resulted in acceleration of sperm maturation in males. In the ovaries of females, a strong inhibition of cyp19a1a gene was observed following exposure to NET at 810 ng/L. Similarly, NET at the highest treatment led to a significant down-regulation of cyp17, cyp19a1a, vasa, nanos1, dazl and dmc1 genes in the testes of males. Taken together, the overall results demonstrated that NET could impact growth and gonadal maturation, with significant alterations of transcriptional expression genes along HPG axis and germ cells.

We proposed a novel strategy in the fabrication of biodegradable poly(acrylic acid-co-acrylamide)/poly(vinyl alcohol) (P(AAc-co-Am)/PVA) double network (DN) hydrogels with good mechanical and self-healing properties. In the DN hydrogel system, P(AAc-co-Am) polymers form a network through the ionic coordinates between –COO– and Fe3+ and hydrogen bonding between –COOH and –CONH2, while another network is fabricated by the complexation between PVA and borax. The influences of the composition on the rheological behaviors and mechanical properties of the synthesized DN hydrogels were investigated. The rheological measurements revealed that the viscoelasticity and stiffness of the P(AAc-co-Am)/PVA DN hydrogels increase as the acrylamide and Fe3+ concentrations increase. At 0.05 mmol of Fe3+ and 50% of acrylamide, tensile strength and elongation at break of P(AAc-co-Am)/PVA DN hydrogels could reach 329.5 KPa and 12.9 mm/mm, respectively. These properties arise from the dynamic reversible bonds existed in the P(AAc-co-Am)/PVA DN hydrogels. These reversible bonds also give good self-healing properties, and the maximum self-healing efficiency of P(AAc-co-Am)/PVA DN hydrogels is up to 96.4%. The degradation test of synthesized DN hydrogels was also conducted under simulated physiological conditions and the weight loss could reach 74% in the simulated intestinal fluid. According to the results presented here, the synthesized P(AAc-co-Am)/PVA DN hydrogels have a potential application prospect in various biomedical fields.

In this paper, poly(styrene-divinylbenzene) foams were synthesized using a high internal phase emulsion (HIPE) technique with Span 80 and with 900 °C calcined oyster shell powder as a co-emulsifier, 2,2′-azobisisobutyronitrile (AIBN) as an initiator and deionized water as the dispersing phase. SEM images revealed that the materials possess a hierarchical porous structure of nano/micro size, which resulted in saturated oil adsorption in only half a minute. The dispersing phase amount was investigated for its effect on adsorption. The optimized foams have 24.8–58.3 g g−1 adsorbencies for several organic solvents, and they demonstrated superhydrophobicity and excellent oleophilicity with the water contact angle (WCA) even close to 149° and oil contact angle approaching 0°. Moreover, the foams displayed high oil retention under pressure. The adsorption–centrifugation cycling results indicated high repeatability of the recovered foams. All of these features predicted the potential applications of superhydrophobic foams in oil–water separation.

The crystallization behavior of a series of synthesized polylactide (PLA)/poly(δ-valerolactone) (PVL) supramolecular copolymers with 2-ureido-4[1H]-pyrimidinone (UPy) groups is investigated by differential scanning calorimetry and X-ray diffraction. The stereocomplexation of PLA-based supramolecular polymers (SMPs) is strongly related to the block length, L/D ratios, and the UPy groups. Both the increase of the PLA block length and the self-complementary hydrogen bonding of the UPy end groups restrain the crystallization of the PVL blocks. The stereocomplexation of PLA-SMPs is greatly promoted by UPy groups, while the homocrystallization of PLA is constrained. The dynamic mechanical analysis indicated that the enhanced stereocomplexation would lead to higher thermal resistance and mechanical properties of PLA-based SMPs.

The synergistic effects of poly(ethylene glycol) (PEG) and polyhedral oligomeric silsesquioxanes (POSS) on the crystallization behavior of semicrystalline poly(L-lactide) (PLLA) were systemically investigated using differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). Initially, the influences of PEG and POSS, individually, on PLLA crystallization were studied. The results indicated that PEG, as an efficient plasticizer, enhanced the mobility of the PLLA chains, resulting in decreasing of the glass transition temperature. The enhanced crystallization capacity of PLLA was strongly dependent on the molecular weight and content of the PEG, increasing with decreasing of the molecular weight and increasing of the PEG content. The experimental results also indicated that POSS was a heterogeneous nucleating agent, promoting the crystallization of PLLA. The synergistic effects of PEG and POSS on PLLA crystallization were then analyzed. The results showed that in the presence of ...

In this study, a series of reinforced polyimide (PI)/carbon fiber (CF) composite foams were fabricated through thermal foaming of polyester ammonium salt (PEAS) precursor powders. The PEAS precursor powders containing different contents of chopped CF were synthesized from benzophenone-3,3′,4,4′-tetracarboxylic dianhydride (BTDA) and 4,4′-diaminodiphenyl ether (ODA). The effects of different CF loadings on foaming behavior of PEAS/CF composite precursor powders, final cellular morphology, and physical properties of PI composite foams were investigated. The results revealed that the chopped CF acted as nucleation agent in the foaming process. The dispersion of CF can be evaluated using digital microscope. It is interesting to find that the chopped CF were highly oriented along the direction of cell arrises. As a result, the mechanical properties of PI foams were significantly enhanced owing to the incorporation of chopped CF. Furthermore, the thermal stability of PI composite foams were also slightly improved owing to fine dispersion of CF. In addition, the PI/CF composite foam shows uniform cell size distribution and the best comprehensive physical properties as chopped CF loading at around 6 wt%. Copyright © 2016 John Wiley & Sons, Ltd.

In this study, several asymmetric poly(L-lactide)/poly(D-lactide) (PLLA/PDLA) blends were prepared by adding small amounts of PDLA with different structures into linear PLLA matrix. The effect of PDLA on rheological behavior, crystallization behavior, nucleation efficiency and spherulite growth of PLLA was investigated. Rheological results indicated that PLLA/PDLA blends showed solid-like viscoelastic behavior at low temperature ( PLLA/L-PDLA > PLLA/3PDLA > PLLA/4PDLA. No-isotherm and isotherm crystallization results indicated that the crystallization capacity of PLLA/PDLA blends was strongly related to the PDLA structure, crystallization temperature and thermal treatment temperature. Furthermore, the dimension of crystal growth during isotherm crystallization presented the obvious dependent on the PDLA structure. The nucleation efficiency of sc-crystallites in the blends and spherulite density during isothermal crystallization were also studied. Nucleation efficiency of sc-crystallites in the PLLA/S-PDLA blends showed the obvious dependent on thermal treatment temperature with respect to PLLA/L-PDLA, and nucleation efficiency sc-crystallites in the PLLA/S-PDLA blends first decreased and then increased as the thermal treatment temperature increased. Spherulite density of PLLA/PDLA blends was also related to thermal treatment temperature and the PDLA structure. This study has discussed the temperature dependence of the stereocomplex networks between PLLA and PDLA with different structure, and then its consequential influence on rheology and crystallization capacity of PLLA, which would provide the theoretical direction for PLA processing. Copyright © 2016 John Wiley & Sons, Ltd.

A series of asymmetric PLLA/PDLA blends based on linear PLLA and PDLA (linear PDLA and star-shaped PDLA) were prepared by solution blending, and stereocomplex crystallites (sc-crystallites) were formed between PLLA and various PDLA due to strong hydrogen bonding. Rheological results indicated that the melt strength of PLLA was improved due to the network structure of sc-crystallites in the PLLA melt. The effect of PDLA on rheological behavior of the melt decreased in the following order: 6PDLA > L-PDLA > 3PDLA > 4PDLA. Dissolution experiment revealed that the formed network structure could be formed by interparticle polymer chains or branched points. Nonisothermal and isothermal crystallization showed that the promoting crystallization of sc-crystallites for PLLA was closely related to thermal treatment temperature, crystallization temperature and the structure of PDLA, and the PDLA structure could change the pattern of crystal growth during isothermal crystallization. Nucleation efficiency of sc-crystallites during non-isothermal crystallization decreased with increasing of arm numbers of PDLA. POM results also demonstrated that the nucleation and spherulite growth during isothermal crystallization were affected by the PDLA structure. This study has systemically investigated the effects of the PDLA structure on rheology and crystallization capacity of asymmetric PLLA/PDLA blends, which would provide potential approaches to control the microstructure and physical performances of PLLA/PDLA blends.

Foamed polylactide (PLA), PLA–PBAT (poly (butylene adipate-co-terphathalate)) blend and their composites with CaCO3 were prepared in a batch process using supercritical carbon dioxide (CO2) at 12 MPa and 45°C. The solubility of CO2 and its diffusion patterns in different PLA samples was investigated. PLA systems had a relatively high CO2 solubility related to the carboxyl groups. CO2 desorption behaviors in PLA systems first followed the Fickian diffusion mechanism in short time and then decreased slowly to a plateau. The addition of both PBAT and CaCO3 into PLA impeded the desorption of CO2. In the presence of second phase PBAT, nanoparticles CaCO3 and dissolved CO2, the PLA crystallization behavior investigated by DSC technique was greatly changed. As the desorption time increased, the gas induced crystallinity slightly decreased in consequence of less CO2 content in each system and thus less plasticization effect. The cell morphology of foamed PLA and PLA composites showed interesting microstructure patterns. The prepared pure PLA foam exhibits a typical bimodal structure because of the foaming in both the amorphous and crystalline zones. With PBAT and CaCO3 into PLA, the composite foam presented significant increase in cell uniformity and cell density. With less CO2 content in each PLA sample, the cell structure showed interesting variation. Pure PLA foam presented transition from bimodal structure to more uniform cell structure with decreased cell density. In contract, PLA–PBAT foam show unfoamed regions because of none CO2 left in the separated PBAT phase. Copyright © 2016 John Wiley & Sons, Ltd.

In this research paper, a series of novel polyimide (PI) foams containing benzimidazole units were prepared derived from polyester ammonium salt (PEAS) precursor powders, which were synthesized by co-polymerization of benzophenone-3,3′,4,4′-tetracarboxylic dianhydride (BTDA) with two diamines of 2-(4-aminophenyl)-5-aminobenzimidazole (BIA) and 4,4′-diaminodiphenyl ether (ODA) with various molar ratios. The effects of incorporation of BIA on the morphology, thermal and mechanical properties of co-polyimide (co-PI) foams were explored. The results show that the BIA has a significant influence on foaming degree of PEAS precursor powders. The density of co-polyimide foams increases with increasing the BIA content in the polymer chains. Moreover, the thermal stability of the resultant co-polyimide foams presents a remarkable upward trend with incorporating more BIA units into the polymer chains. As the BIA loading up to 30 mol%, the glass transition temperature of co-polyimide foams increases around 50 °C in comparison with the pristine polyimide foam. Furthermore, the compressive strength of the co-polyimide foams is in the range of 0.30–0.75 MPa, which is superior to their of commercial polyimide foams with the same density. The co-polyimide foams with higher thermal and mechanical properties expand their potential application in many high-tech fields such as aerospace and aviation industries.

Herein, we describe a simple and cost-effective design for the fabrication of a novel ternary RGO/BiOCl/TiO2 nanocomposites through a simple hydrothermal process. The prepared nanocomposites were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), X-ray diffraction (XRD), UV&ndash, vis diffuse reflectance spectroscopy (UV&ndash, vis DRS) and N2 adsorption&ndash, desorption analysis. Organic contaminants&mdash, such as methylene blue (MB), methyl orange (MO), rhodamine B (RhB) and amido black-10B (AB-10B)&mdash, were employed as the target pollutants to evaluate the adsorption capacity and photocatalytic activity of RGO/BiOCl/TiO2 nanocomposites. From experimental data, it was also found that the amount of TiO2 impressed the photocatalytic performance, and the nanocomposites with 10% of TiO2 showed the best photocatalytic activity. The improved photocatalytic performance may be mainly due to the narrow band gap, and the charge separation and migration of RGO. Moreover, good recyclability was obtained from RGO/BiOCl/TiO2 nanocomposites, and scavenger tests indicated that photogenerated holes were the main active species in the reaction system. Therefore, the prepared RGO/BiOCl/TiO2 nanocomposites have broad applications foreground in pollutants purification.

Asymmetric poly(L-lactide)/poly(D-Lactide) (PLLA/PDLA) blends were prepared by adding small amounts of PDLA into the PLLA matrix with the formation of stereocomplex crystallites (sc-crystallites). Rheological results indicated that the PLLA/PDLA melt at lower temperatures (

In this study, stereocomplexed poly(lactide) (PLA) was investigated by blending linear poly(l-lactide) (PLLA) and tri-block copolymer poly(d-lactide) − (polyethylene glycol) − poly(d-lactide) (PDLA-PEG-PDLA). Synthesized PDLA-PEG-PDLA tri-block copolymers with different PEG and PDLA segment lengths were studied and their influences on the degree of sterecomplexation and non-isothermal crystallization behaviour of the PLLA/PDLA-PEG-PDLA blend were examined in detail by DSC, XRD and polarized optical microscopy. A full stereocomplexation between PLLA and PDLA-PEG4k-PDLA200 could be formed when the L/D ratio ranged from 7/3 to 5/5 without the presence of PLA homocrystals. The segmental mobility and length of both PEG and PDLA are the dominating factors in the critical D/L ratio to achieve full stereocomplexation and also for nucleation and spherulite growth during the non-isothermal crystallization process. For fixed PEG segmental length, the stereocomplexed PLA formed showed first an increasing and then a decreasing melting temperature with increasing PDLA segments due to their intrinsic stiff mobility. Furthermore, the effect of PEG segmental mobility on PLA stereocomplexation was investigated. The results clearly showed that the crystallization temperature and melting temperature of stereocomplexed-PLA kept increasing with increasing PEG segmental length, which was due to PEG soft mobility in the tri-block copolymers. However, PEG was not favourable for nucleation but could facilitate the spherulite growth rate. Both the PDLA and PEG segmental lengths in the tri-block copolymers affect the crystallinity of stereocomplexed-PLA and the stereocomplexation formation process; they have a different influence on blends prepared by solution casting or the melting method. © 2015 Society of Chemical Industry

Four-armed star poly(l-lactide) grafted multiwalled carbon nanotubes (CNTs-g-4PLLA) were synthesized through the nucleophilic substitution reaction between 4PLLA and acryl chloride of CNTs and then characterized by transmission electron microscope, X-ray photoelectron spectroscopy, thermal gravimetric analysis (TGA), and ultraviolet visible spectrophotometer. The results indicated that 4PLLA was successfully grafted onto CNTs, and CNTs-g-4PLLA contained 37.7 wt% of 4PLLA. PLLA/CNTs-g-4PLLA nanocomposites were prepared by solution casting with different CNTs-g-4PLLA content. Rheological behavior of PLLA/CNTs-g-4PLLA nanocomposites was measured using a rheometer. The result showed that CNTs-g-4PLLA formed a network structure at percolation concentration, which improves obviously rheological properties of PLLA in the molten state. The crystallization behavior and crystal structure of the nanocomposites were comprehensive evaluated through differential scanning calorimetry, X-ray diffraction, and polarizing optical microscope. The results found that CNTs-g-4PLLA played two roles in PLLA crystallization. The addition of CNTs-g-4PLLA acted as nucleating agent and obviously accelerated the spherulites growth under percolation concentration, while it inhibited the movement of PLLA chains at above percolation concentration, resulting in the decrease of crystallinity. Thermal stability and mechanical properties of the nanocomposites were also investigated using TGA, dynamic mechanical analysis, and tensile test. These results indicated that the incorporation of CNT-g-4PLLA into the PLLA matrix improved the thermal stability, storage modulus, and tensile strength of the nanocomposites. POLYM. COMPOS., 2015. © 2015 Society of Plastics Engineers

Poly(L-lactide) (PLLA) composites with TiO2-g-poly(D-lactide) (PDLA), which was synthesized by surface-initiated opening ring polymerization with TiO2 as initiator and Sn(Oct)2 as catalyst, were prepared by solution casting. The synthesized TiO2-g-PDLA was characterized by transmission electron microscope (TEM) and dynamic laser scattering (DLS), showing larger size corresponding to that of TiO2. Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) measurements were further carried out and indicated that PDLA was grafted onto TiO2 through covalent bond. For PLLA/TiO2-g-PDLA composites, the stereocomplex crystallites were formed between PDLA grafted on the surface of TiO2 and the PLLA matrix, which was determined by FT-IR, differential scanning calorimetry (DSC), and X-ray diffractometer (XRD). The influence of stereocomplex crystallites on the rheological behavior of PLLA/TiO2-g-PDLA was investigated by rheometer, which showed greater improvement of rheological properties compared to that of PLLA/TiO2 composites especially with a percolation content of TiO2-g-PDLA between 3 wt%–5 wt%. The crystallization and melting behavior of PLLA/TiO2-g-PDLA composites were studied by DSC under different thermal treatment conditions. The formed PLA stereocomplex network acted as nucleating agents and a special interphase on the functional surface of TiO2, which resulted in imperfect PLLA crystal with lower melting temperature. When the thermal treatment was close to the melting temperature of PLA stereocomplex, the crystallinity approached to the maximum. The isothermal crystallization study by polarizing microscope (POM) indicated that stereocomplex network presented stronger nucleation capacity than TiO2-g-PDLA. Copyright © 2015 John Wiley & Sons, Ltd.

Adsorbents based on natural polysaccharides have attracted increasing interest because of their low-cost and biodegradability, particularly, polysaccharide-based nanocomposite adsorbents. In this study the xylan/poly(acrylic acid) magnetic nanocomposite hydrogel adsorbent was prepared from wheat straw xylan and Fe3O4 nanoparticles, and its adsorption property was studied on methylene blue removal. The prepared hydrogel adsorbent had a semi-interpenetrating network structure and exhibited a macro-porous structure with interconnected porous channels. Super-paramagnetic characteristic behavior was observed from magnetic analysis using a vibrating sample magnetometer. The optimum condition for methylene blue adsorption on the adsorbent was found at pH 8 with an adsorbent dosage of 3g/L and an initial concentration of 400mg/L, and the removal percentage reached above 90%. The adsorption isotherm of methylene blue on the prepared hydrogel adsorbent was fitted to the Langmuir model, and the pseudo-second-order kinetic model could describe the adsorption process. All obtained results indicated that the prepared hydrogel adsorbent is promising for water treatment applications.

Functionalized carbon nanotubes (F-CNTs) were synthesized through the nucleophilic substitution reaction between four-armed star poly(d-lactide) (4PDLA) and acryl chloride of carbon nanotubes and were characterized using Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and thermogravimetric analysis. The results indicated that the 4PDLA was successfully grafted onto carbon nanotubes, and it contained 45.5 wt% of 4PDLA. Poly(l-lactide) (PLLA) nanocomposites with different F-CNTs content were prepared by solution casting. Optical microscopy and scanning electron microscopy results showed that F-CNTs were uniformly dispersed in the nanocomposites. Crystallization behavior and crystal structure of PLLA nanocomposites were investigated using differential scanning calorimetry, polarizing microscope and X-ray diffraction. The results found that poly(lactide) stereocomplex crystal could be formed between PLLA and F-CNTs. F-CNTs played different roles in the process of solution casting and melting crystallization. Polarizing microscope also revealed that crystallization temperature had a significant effect on the nucleation and spherulites growth of PLLA. Thermal stability and mechanical properties of the nanocomposites were also investigated by thermogravimetric analysis, dynamic mechanical analysis and tensile testing. These results demonstrated that the addition of F-CNTs obviously improved thermal stability and tensile strength of PLLA. The results showed that PLLA/F-CNTs would have potential values in engineering fields. Copyright © 2015 John Wiley & Sons, Ltd.

Stereocomplex poly(lactide) (PLA) was obtained by solution blending of linear PLLA and PDLA-PEG-PDLA. Effects of the L/D ratios, PEG block, and PDLA block on stereocomplexation of the blends are systemically discussed. The full stereocomplex PLA can be acquired by solution blending when L/D ratios are in the range of 7/3–5/5. The experiment results demonstrated that the stereocomplex degree of PLLA/PDLA-PEG-PDLA prepared by melt blending was closely related to the PEG block and PDLA block. POM results indicated that the blends with high L/D ratio showed large disordered spherulites, and the typical Maltese cross pattern was observed as the L/D ratios decreased. The results of PEG block on the stereocomplexation of PLLA/PDLA-PEG-PDLA revealed that the PEG blocks possessed two sides: accelerating agent for the mobility of polymer chains and decreasing nucleation capacity due to their diluting effect. The effect of PDLA block on the stereocomplexation of the blends was also well investigated. The results showed that the crystallization of sc-crystallites and hc-crystallites in the PLLA/PDLA-PEG4k-PDLA blends with different PDLA blocks presents an obvious competition relationship, and this is not beneficial to the formation of sc-crystallites with increasing PDLA block. The melting behavior of PLLA/PDLA-PEG4k-PDLA with different PDLA blocks after isothermal crystallization showed that the blends could achieve full stereocomplex when the crystallization temperature exceeded 160 °C, and a crystallite with high perfection could be formed as the crystallization temperature increased. This study systemically investigated the effects of the L/D ratios, PEG block, PDLA block, and crystallization conditions on stereocomplex crystallization of PLLA/PDLA-PEG-PDLA blends, which can provide potential approaches to control the microstructure and physical performances of PLLA/PDLA-PEG-PDLA blends.

A novel magnetic semi-IPN hydrogel based on xylan and poly(acrylic acid) was prepared, and the prepared hydrogels had excellent thermal stability, magnetic-, and pH- sensitive properties. The physical-chemical properties of the prepared hydrogels depended on the contents of xylan and Fe3O4 nanoparticles. The thermal stability of the hydrogels enhanced as the contents of xylan and Fe3O4 nanoparticles increased; however, the equilibrium swelling ratio decreased with increasing the contents of Fe3O4 nanoparticles and xylan. The interconnected pore channels were formed in the hydrogels and the amount of the channels increased with an increase in xylan content. The prepared hydrogels had a super-paramagnetic property, and the magnetization increased with an increase in the content of Fe3O4 nanoparticles. The superior characteristics of the xylan/PAAc magnetic semi-IPN hydrogel would expand its applications in drug delivery and magnetic separation aspects. POLYM. COMPOS., 2014. © 2014 Society of Plastics Engineers

A novel superabsorbent was prepared by the copolymerization reaction between multiwalled carbon nanotubes (MWCNTs)–xylan composite and poly(methacrylic acid) (PMAA) in the presence of N,N′-methylenebisacrylamide as cross-linker and the redox initiation system (NH)4S2O8-anhydrous Na2SO3 as initiator for adsorbing methylene blue (MB) from aqueous solution. First, covalent modification of MWCNTs with a natural polymer xylan was achieved by the nucleophilic substitution reaction. The obtained xylan modified MWCNTs–xylan composite was characterized by transmission electron microscope, Fourier transform infrared spectroscopy, X-ray photoelectron spectrometer, and thermal gravimetric analysis. The results indicated that the hydroxyl groups of xylan participated in the formation of MWCNTs–xylan composite, and MWCNTs–xylan composite contained 32% xylan and about four molecule chains of xylan were grafted onto 5,000 carbon atoms of MWCNTs sidewalls. Subsequently, a novel superabsorbent based on MWCNTs–xylan composite and PMAA was prepared and characterized by Fourier transform infrared spectroscopy, scanning electron microscope, and swelling test. The results proved that superabsorbent was successfully prepared by copolymerization reaction and found that the superabsorbent evidently presented three-dimensional network structure. Swelling process of superabsorbent complied with the Fick's law. Adsorption property of superabsorbent for MB was also systematically studied by investigating these parameters, such as superabsorbent dosage, initial MB concentration, contact time, ion strength, and pH. The superabsorbent presented a higher adsorption capacity and removal rate for MB. The adsorption data were fitted by Langmuir, Freundlich isotherm models, and four adsorption kinetic models. Freundlich isotherm model better fitted the equilibrium data than Langmuir, and adsorption kinetics could be well described by pseudo-second-order kinetic and intraparticle diffusion. These results indicated that the superabsorbent can be used as an efficient absorbent for removal of MB from aqueous solution. POLYM. COMPOS., 35:1516–1528, 2014. © 2013 Society of Plastics Engineers

An organic–inorganic composite hydrogel was prepared based on hemicellulose and multi-wall carbon nanotubes. The effects of hydrogel amount, initial concentration, contact time, and salt concentration on the adsorption performance of the prepared hydrogels were observed using methylene blue as a model hazardous material. The results indicated that the adsorption kinetic of methylene blue on the prepared adsorbent was well fitted to the pseudo-second-order kinetic model and the adsorption isotherm conformed to the Freundlich model. Removal percentage of methylene blue increased with increased adsorbent amount and kept higher than 98% when adsorbent amount was above 6 g L 21 . Adsorption amount of methylene blue on the prepared adsorbent also increased when increasing initial concentration over the range from 50 to 500 mg L 21 . Both of adsorption amount and removal percentage increased with an increase in the contact time, and removal efficiency obviously deteriorated as salt concentration increased. All obtained results reported that the prepared composite hydrogel would have an application prospect in water treatment. POLYM. COMPOS., 35:45–52, 2014. V C 2013 Society of Plastics Engineers

Hydrogels based on hemicellulose of wheat straw were prepared as a novel carrier for controlled drug delivery. The chemical structure and morphology of the hydrogels were characterised using FT-IR and SEM, respectively. The swelling ratios of the hydrogels were determined, and the results showed that the hydrogels were pH-responsive. The swelling kinetics of the hydrogels followed a Fickian diffusion process in media with a pH of 1.5, and water uptake was controlled collaboratively by hydrogel relaxation and water diffusion in media with pH values of 7.4 and 10.0. The degradation test of the hydrogels was conducted under simulated physiological conditions, and both hemicellulose content and the crosslinking density of the hydrogels were major factors that affected the biodegradability of the hemicellulose-based hydrogels. A comparison of the in vitro release of acetylsalicylic acid and theophylline indicated that the drug release was controlled both by the hydrogel and by the intrinsic character of the drug. According to the results presented here, hemicellulose-based hydrogels can be used in biomedical fields, especially for controlled drug release.

In this research, a series of porous copolyimide (co-PI) films containing trifluoromethyl group (CF3) were facilely prepared via a phase separation process. The co-PI were synthesized by the reaction of benzophenone-3,3′,4,4′-tetracarboxylic dianhydride (BTDA) with two diamines of 4,4′-diaminodiphenyl ether (ODA) and 3-trifluoromethyl-4,4'-diaminodiphenyl ether (FODA) with various molar ratios. The flexible and tough porous co-PI films with about 300 μm thickness and 8∼10 μm average diameter could be obtained by solution casting conveniently. The thermal properties of the obtained porous co-PI films were excellent with a glass transition temperature at 270 °C ∼ 280 °C and only 5% weight loss in temperature from 530 °C to 560 °C under nitrogen atmosphere. In addition, the dielectric and hydrophobic properties of porous co-PI films were remarkably improved owing to the presence of trifluoromethyl groups (CF3) in the polymer chains. Moreover, our synthesized porous co-PI films also showed good mechanical properties. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 134, 44494.

Structural characterization and isolation of lignin and hemicelluloses from crops are very important for industrial utilization. In this paper, the sequential treatments of barley straw using 90% dioxane, 80% acidic dioxane, 100% dimethyl sulfoxide, and 8% NaOH released total 93% of original lignin and 87% of original hemicelluloses. The extractions with acidic dioxane and dimethyl sulfoxide produced the original hemicelluloses and high-condensed lignin mainly from the middle lamella. FT-IR and NMR analyses show that the hemicelluloses of barley straw contain acidic arabinxylans as the major polysaccharides, which are substituted by α- l -arabinofuranose, 4-O-methyl-glucuronic acid, acetyl group (DS = 0.13), and xylose at O-3 and/or O-2 of xylan, and lignin contains β-O-4′ as a predominant interunit linkage with high amounts of β-5′ and β-1′. The guaiacyl and syringyl units are more etherified, and the proportion of erythro-β-O-4′ is slightly higher than that of threo-β-O-4′ in the lignin of barley straw.

Supramolecular poly(ɛ-capolactone)/poly(lactide) alternating multiblock copolymers were prepared by UPy-functionalized poly(lactide)-b-poly(ɛ-capolactone)-b-poly(lactide) copolymers. The prepared supramolecular polymers (SMPs) exhibit the characteristic properties of thermoplastic elastomers. The stereo multiblock SMPs (sc-SMPs) were formed by blending UPy-functionalized poly(l-lactide)-b-PCL-b-poly(l-lactide) (l-SMPs) and UPy-functionalized poly(d-lactide)-b-PCL-b-poly(d-lactide) (d-SMPs) due to stereocomplexation of the PLLA and PDLA blocks. Sc-SMPs with low content of d-SMPs (≤20%) are transparent, elastic solids, while those having high d-SMPs content are opaque, brittle solids. The effects of l-SMPs/d-SMPs mixing ratios on thermal, crystallization behaviors, crystal structure, mechanical and hydrophilic properties of sc-SMPs were deeply investigated. The incorporation of UPy groups depresses the crystallization of polymer, and the stereocomplex formation accelerates the crystallization rate. The used initiator functionalized polyhedral oligomeric silsesquioxanes causes a different effect on the crystallization of PLA and PCL blocks. The tensile strength and elongation at break of ld/dd-SMPs (d represents the initiator diethylene glycol) are significantly larger than that of lp/dp-SMPs (p represents the initiator polyhedral oligomeric silsesquioxanes), and their heat resistance and hydrophilicity can be also modulated by the l-SMPs/d-SMPs mixing ratios and the different initiators. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45575.

A stimuli-responsive porous hydrogel was synthesized from wheat straw hemicellulose using CaCO3 as the porogen, and its application for the removal of methylene blue was studied. The porous structure of the prepared hydrogel was confirmed by SEM analysis. The effects of pH and polyelectrolyte on the swelling of the hydrogels were discussed, and the porous hydrogels showed excellent sensitivity to pH and salt. The deswelling kinetic study indicated that the hydrogels exhibited rapid shrinking in NaCl aqueous solutions. The methylene blue adsorption on the hydrogels was investigated, and the obtained adsorption data was fitted to the pseudo-first-order, pseudo-second-order and intra-particle diffusion kinetics models, and the pseudo-first-order kinetic model could describe the adsorption process, and the adsorption process of methylene blue on the hydrogels was controlled by external film diffusion. This study reported that the hemicellulose-based porous hydrogel is promising for water treatment. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41606.