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In order to improve the wear-resistant properties of polymer composites, a common approach is to introduce high-strength or lubricating components in composites, but the mechanical properties of composites are generally significantly reduced. It is still a challenge to obtain excellent wear resistance as well as good mechanical properties. In this work, a new ultrahigh molecular polyethylene (UHMWPE)/polycrystalline mullite fiber (PMF) composite was developed to simultaneously improve the tribological properties and the mechanical properties. The wear rate (K0) of UHMWPE/PMF reduced drastically [≈10–5 mm3/(N·m)] to about 2.5% of K0 of original UHMWPE. And the tensile strength and the elongation at break of UHMWPE/PMF remained at 97.0% and 90.0% of pure UHMWPE, respectively. These improvements are related to the higher crystallinity of UHMWPE/PMF (UHMWPE/PMF: 49.2%; UHMWPE: 41.2%), the larger crystallite sizes (UHMWPE/PMF: 21.0 nm; UHMWPE: 12.0 nm), and the high hardness and excellent mechanical strength of PMF. The simple processing of UHMWPE/PMF composites by adding PMF to increase the tribological properties is low cost and attractive, which has a great potential application in the fabrication of highly wear-resistant materials. [ABSTRACT FROM AUTHOR]

• A facile and practical melt blending to prepare antimicrobial PET was proposed. • The antimicrobial PP- g -PHMG enriched on the surfaces of PET materials. • The PET materials had excellent antimicrobial activities and nonleaching characteristic. Antimicrobial poly(ethylene terephthalate) (PET) materials are highly demanding in various applications in the industry. However, the combination of large-scale preparation, cost-effective and nonleaching characteristic still remains challenges. Herein, antimicrobial PET materials were prepared by an easy-to-scale-up melting blending between neat PET and polypropylene grafted poly(hexamethylene guanidine) (PP- g -PHMG). Such PET materials exhibited excellent antimicrobial activities, such as above 98.0% and 99.9% of inhibition rates against Escherichia coli and Staphylococcus aureus , respectively. Nonleaching characteristic was confirmed by the inhibition zone test. More importantly, the antimicrobial component enriched on the surfaces of PET materials due to the difference in the compatibility between PET matrix and PP- g -PHMG and the heterogeneous repulsive effect of crystallization. This work provides a facile and easy-to-scale-up way to obtain nonleaching antimicrobial PET. [ABSTRACT FROM AUTHOR]

Background: Gemcitabine is a cornerstone drug for the treatment of all stages of pancreatic cancer and can prolong the survival of patients with pancreatic cancer, but resistance to gemcitabine in pancreatic cancer patients hinders its efficacy. The overexpression of Early growth response 1(EGR1) in pancreatic ductal adenocarcinoma as a mechanism of gemcitabine chemoresistance in pancreatic cancer has not been explored. The major mechanisms of gemcitabine chemoresistance are related to drug uptake, metabolism, and action. One of the common causes of tumor multidrug resistance (MDR) to chemotherapy in cancer cells is that transporter proteins increase intracellular drug efflux and decrease drug concentrations by inducing anti-apoptotic mechanisms. It has been reported that gemcitabine binds to MDR1 with high affinity. The purpose of this research was to investigate the potential mechanisms by which EGR1 associates with MDR1 to regulate gemcitabine resistance in pancreatic cancer cells. Methods: The following in vitro and in vivo techniques were used in this research to explore the potential mechanisms by which EGR1 binds to MDR1 to regulate gemcitabine resistance in pancreatic cancer cells. Cell culture; in vitro and in vivo study of EGR1 function by loss of function analysis. Binding of EGR1 to the MDR1 promoter was detected using the ChIP assay. qRT-PCR, Western blot assays to detect protein and mRNA expression; use of Annexin V apoptosis detection assay to test apoptosis; CCK8, Edu assay to test cell proliferation viability. The animal model of pancreatic cancer subcutaneous allograft was constructed and the tumours were stained with hematoxylin eosin and Ki-67 expression was detected using immunohistochemistry. Findings: We revealed that EGR1 expression was increased in different pancreatic cancer cell lines compared to normal pancreatic ductal epithelial cells. Moreover, gemcitabine treatment induced upregulation of EGR1 expression in a dose- and time-dependent manner. EGR1 is significantly enriched in the MDR1 promoter sequence.Upon knockdown of EGR1, cell proliferation was impaired in CFPAC-1 and PANC-1 cell lines, apoptosis was enhanced and MDR1 expression was decreased, thereby partially reversing gemcitabine chemoresistance. In animal experiments, knockdown of EGR1 enhanced the inhibitory effect of gemcitabine on tumor growth compared with the sh-NC group. Conclusions: Our study suggests that EGR1 may be involved in the regulation of MDR1 to enhance gemcitabine resistance in pancreatic cancer cells. EGR1 could be a novel therapeutic target to overcome gemcitabine resistance in pancreatic cancer. [ABSTRACT FROM AUTHOR]

Many efforts have been devoted to developing functional poly(ethylene terephthalate) (PET) due to its special biomedical applications in surgical meshes, heart valves, vascular grafts, artificial ligaments, etc. However, for antimicrobial PET the release of antimicrobial component remains a concern. In this work, an antimicrobial compound with terminal epoxy group was synthesized by ethylene glycol diglycidyl ether (EGDE) and polyhexamethylene guanidine hydrochloride (PHMG). Then, EGDE-PHMG was chemically bonded with PET surface through a reaction between the epoxy group of EGDE-PHMG and the amino group of aminated PET to generate non-leaching and permanent antimicrobial PET. The content of PHMG on PET surface, morphology and hydrophilicity of surface, antimicrobial activity and mechanical property of PET were investigated. The amount of EGDE-PHMG on PET surface reached at 3.96 nmol/cm2, resulting in excellent antimicrobial activities against Escherichia coli and Staphylococcus aureus with above 99.99% of inhibition rates. Due to the good hydrophilicity, excellent antimicrobial property, non-leaching characteristic of antimicrobial component and good mechanical properties, the as-prepared antimicrobial PET was promising in the biomedical applications. [ABSTRACT FROM AUTHOR]

Taking advantage of the self-assembly between the components, novel stable antibacterial nanoparticles were efficiently fabricated via a facile one-step co-polymerization of acrylic acid (AA) and N , N ′-methylenebisacrylamide (MBA) on a mixed aqueous solution of poly(hexamethylene guanidine hydrochloride) (PHMG) and hydroxyethylcellulose (HEC). The z -average hydrodynamic diameters of the nanoparticles ranged from 220 nm to 450 nm. The inner layer of the nanoparticles is composed of water-insoluble interpolymer complexes of PHMG and PAA networks, while the outer layer is composed of PHMG and HEC. The nanoparticles are stabilized by electrostatic interactions, hydrogen bonding interactions, and the chemical bonds. The nanoparticle solution remained stable in a wide pH range of 2.0–12.0 and at salt concentrations below 0.25 mol/L. The nanoparticles were incorporated into handsheets using a dipping treatment. The resulted handsheets exhibited excellent antimicrobial activities even after multiple water washing treatments. The nanoparticles are promising in fabricating paper, water-based coatings and textiles with permanent antibacterial activity. [ABSTRACT FROM AUTHOR]

The antimicrobial thermoplastic starch (ATPS) containing guanidine-based polymers was obtained using a twin-screw extrusion with potato starch and polyhexamethylene guanidine hydrochloride (PHGH). Furthermore, the non-leaching antimicrobial biodegradable poly(butylene adipate-co-terephthalate) (PBAT) was prepared through reactive extrusion with PBAT and ATPS in the presence of the coupling agent, 2,2′-(1,3-phenylene)-bis (2-oxazoline) (PBO). Finally, the antimicrobial PBAT films were obtained by using a blown film extrusion system. The mechanical properties of the antimicrobial PBAT films varied with the contents of ATPS and thermoplastic starch (TPS). According to the test results of shaking flask method, the prepared antimicrobial PBAT films showed excellent antimicrobial activities (antimicrobial rate > 99.99%) and rapid pathogen deactivation efficiency (antimicrobial rate > 99.99% even within 15 s of contact time). The water washing and ring diffusion tests demonstrated that the antimicrobial film was a non-leaching product. Inspiringly, the antimicrobial PBAT films with an excellent antimicrobial activity can be obtained even at a very low dosage of PHGH (1.0 mg/g PBAT film). [ABSTRACT FROM AUTHOR]

The biodegradable poly(butylene adipate-co-terephthalate)(PBAT)/thermoplastic starch (TPS) composite has received considerable attention because of the environmental concerns raised by solid waste disposal. However, the application of PBAT/TPS blends was limited due to the poor mechanical properties originating from the incompatibility between PBAT and TPS. In this work, two approaches were developed to improve the mechanical properties of PBAT/TPS blends. One approach is to use compatibilizers, including the synthesized reactive compatibilizer – a styrene–maleic anhydride–glycidyl methacrylate (SMG) terpolymer, and the commercial compatibilizer (Joncryl-ADR-4368). The chemical structures of SMG were analyzed with 1 H NMR and FT-IR. The other approach is to use the modified PBAT (M-PBAT) to replace part of PBAT in the PBAT/TPS blends. M-PBATs with higher molecular weight were obtained via reactive extrusion of PBAT in the presence of a chain extender. The better dispersion of TPS in PBAT was observed in SEM images when using M-PBAT, leading to the higher tensile strength and elongation at break of PBAT/TPS blends. However, the elongation at break decreased in the presence of compatibilizer (SMG or 4368), though the tensile strength remained in a similar level or slightly higher. Overall, the tensile strength and the elongation at break of the resulting biodegradable PBAT/M-PBAT/TPS blends (TPS = 40 wt%) were above 27.0 MPa and 500%, respectively, which is promising for various applications, including packaging and agricultural mulching films. [ABSTRACT FROM AUTHOR]

Recently, biodegradable polymers have been broadly used in various applications, including antimicrobial biodegradable composite materials. However, the biodegradability of such polymers in the presence of antimicrobial agents has barely been investigated. Moreover, whether the antimicrobial property of the material would be compromised or affected by the microorganisms in the soil is still unclear. In this work, the biodegradation behavior and antimicrobial property of the novel antimicrobial biodegradable poly(butylene adipate-co-terephthalate) (PBAT)/thermoplastic starch films before and after a three-month soil burial test have been investigated. The weight retention data showed that both PBAT and starch were still able to degrade even in the presence of the antimicrobial substance, polyhexamethylene guanidine hydrochloride (PHGH). However, the biodegradation rate was retarded. The antimicrobial films exhibited excellent growth inhibition against E. coli before biodegradation test. The film with the coupling agent 2,2′-(1,3-phenylene)-bis(2-oxazoline) (PBO) and less starch content presented a growth inhibition over 99% even after the three-month biodegradation test, due to a better PHGH retention. The semi-crystalline PBAT did not show any significant crystal structure change in the DSC analysis. Both SEM images and mechanical properties demonstrated the biodegradation of the films from the macro-scale. [ABSTRACT FROM AUTHOR]

More information regarding the bactericidal properties of polyhexamethylene guanidine hydrochloride (PHMG) against clinically important antibiotic-resistant ESKAPE ( Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) pathogens needs to be provided for its uses in infection control. The bactericidal properties of PHMG and chlorhexidine digluconate (CHG) were compared based on their minimum inhibitory concentrations (MICs), minimum bactericidal concentrations, and time-course-killing curves against clinically important antibiotic-susceptible and antibiotic-resistant ESKAPE pathogens. Results showed that PHMG exhibited significantly higher bactericidal activities against methicillin-resistant Staphylococcus aureus, carbapenem-resistant Klebsiella pneumoniae, and ceftazidime-resistant Enterobacter spp. than CHG. A slight bactericidal advantage over CHG was obtained against vancomycin-resistant Enterococcus faecium, ciprofloxacin- and levofloxacin-resistant Acinetobacter spp., and multidrug-resistant Pseudomonas aeruginosa. In previous reports, PHMG had higher antimicrobial activity against almost all tested Gram-negative bacteria and several Gram-positive bacteria than CHG using MIC test. These studies support the further development of covalently bound PHMG in sterile-surface materials and the incorporation of PHMG in novel disinfectant formulas. [ABSTRACT FROM AUTHOR]

Antimicrobial packaging films havebeen widely used in variousapplications. However, because of concerns regarding safe food andconsumer demands for preservative-free products, the antimicrobialagents applied to packaging have to be highly effective and the leachingeffect is not allowed. In the present work, the antimicrobial agentpolyhexamethylene guanidine hydrochloride was compounded with starchto prepare antimicrobial thermoplastic starch (ATPS). ATPS was thenmelt-blended with linear low-density polyethylene (LLDPE) to preparethe novel antimicrobial packaging film. The resultant LLDPE/ATPS filmsexhibited excellent antimicrobial properties against Escherichiacoliin the shaking-flask test. The ring-diffusion test furtherconfirmed the nonleaching effect of the films. However, the additionof ATPS decreased the crystallinity of LLDPE. Both rheological analysisand scanning electron microscopy images indicated that a high ATPScontent might result in poor compatibility even in the presence ofa compatibilizer. [ABSTRACT FROM AUTHOR]

Cationic star polymers as drug/gene carriers have attracted increasing attention. Herein, environmental sensitivities and star-shaped architecture were combined into a well-defined gene carrier system, and further amphiphilic modification was conducted. The thermo- and pH-sensitive behaviors of poly[N,N-(dimethyl amino)ethyl methacrylate] (PDMAEMA) star polymers before and after amphiphilic modification in aqueous solutions were investigated. The observed lower critical solution temperature (LCST) increased with increasing arm length due to the increase of hydrophilicity. A significant decrease of the LCSTs with increasing pH and ionic-strength of the solution was found. The incorporation of MMA and BA lipophilic moieties decreased the LCST of the cationic star polymer due to enhanced hydrophobic interaction. As a potential gene carrier, the performance of star polymers on binding DNA was primarily evaluated via particle size, zeta potential, and gel retardation measurements. All the complexes formed stable small particles with diameter of 100∼150 nm at N/P ratio higher than 3.0. The electrostatic screening effect and facilitation for the interaction of complexes with cell membrane induced by the incorporation of lipophilic units were expected to enhance the gene transfection efficiency. [ABSTRACT FROM PUBLISHER]

Highlights: [•] A permanently anti-microbe PP was prepared by a chemical bonding method. [•] The resulting PP showed enhanced killing activities against bacterium and fungi. [•] The antimicrobial PP kept antimicrobial activities after 10days water washing. [•] Guanidine-based antimicrobial polymers were dispersed in PP in a nanometer scale. [•] PP fabrics showed safe results in vivo and in vitro due to the chemical bonding. [Copyright &y& Elsevier]

Abstract: Polyhexamethylene guanidine hydrochloride (PHMG) possesses great potential in the development of covalently bound permanent sterile-surface materials for hospital infection control. This study aimed at evaluating the extensive activity of PHMG and its three novel analogs, including polybutamethylene guanidine hydrochloride, polyoctamethylene guanidine hydrochloride (POMG) and poly(m-xylylene guanidine hydrochloride), against 370 clinical strains, especially 96 isolates of which were antibiotics-resistant. Their in vitro antimicrobial activities were determined by testing the minimal inhibitory concentration (MIC) and time-killing curves. POMG, the novel oligoguanidine had significantly lower MIC values (0.5–16mg/L) against 370 antibiotics-susceptible and -resistant clinical strains compared to PHMG (1–64mg/L) and chlorhexidine digluconate (2–64mg/L). Interestingly, POMG displayed excellent activity against meticillin resistant-Staphylococcus aureus (1–8mg/L) and -coagulase-negative staphylococci (1–2mg/L), vancomycin resistant Enterococcus faecium (2–4mg/L), multidrug resistant Pseudomonas aeruginosa (8–16mg/L), ceftazidime resistant-Citrobacter spp. (1–4mg/L) and -Enterobacter spp. (2–4mg/L). PHMG was especially efficient against methicillin resistant-S. aureus and -coagulase-negative staphylococci (1–8mg/L). The presented extensive activity of POMG and PHMG against antibiotic-resistant bacteria provides encouraging reference information for the using and further development of cationic guanidine-based polymers in the biomedical material field. [Copyright &y& Elsevier]

Abstract: Polyguanidine oligomers, particularly polyhexamethylene biguanide (PHMB) oligomer, are used extensively and safely as disinfectants and biocides. The antibacterial activity of PHMB is attributed to its interaction with cellar membrane components. However, the detailed molecular structures and components of polyguanidine oligomers are still vague and remain to be learned. In this paper, polyhexamethylene guanidine oligomer (PHMG) was prepared by polycondensation of hexamethylenediamine and guanidine hydrochloride, and its molecular structure and components were analyzed in detail using an electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS). Seven types of molecular structures of PHMG were determined, including three linear types and four cyclic or branched ones, and their relative contents varied with reaction conditions. Furthermore, the relationship between the antibacterial activity and weight-average molecular weight (M w) of PHMG was investigated. The results showed that an aqueous solution of PHMG (M w >640) at a concentration as low as 1.0 ppm exhibited an antibacterial rate above 90.0%. [Copyright &y& Elsevier]

Objective: The exact mechanism and target molecules of liver fibrosis have remained largely elusive. Here, we investigated the role of long noncoding RNA Gm9866(lncRNA-Gm9866) on liver fibrosis. Methods: The transcription of lncRNA-Gm9866 in activated cells and mouse fibrotic livers was determined by quantitative polymerase chain reaction (qRT-PCR). The effects of lentivirus-mediated knockdown or overexpression of lncRNA-Gm9866 in liver fibrosis were examined in vitro and in vivo. Furthermore, bioinformatics analysis, cell samples validation, fluorescence in situ hybridization (FISH) co-localization, RNA binding protein immunoprecipitation (RIP), actinomycin D test and Western blot (WB) were carried out to explore the potential mechanism of lncRNA-Gm9866. Results: The expression of α-smooth muscle actin (α-SMA), Collagen I (COL-1) and lncRNA-Gm9866 were significantly increased in tissues and cells. Overexpressing lncRNA-Gm9866 promoted the activation of hepatic stellate cells (HSCs). Silencing lncRNA-Gm9866 inhibited the activation of HSCs and transforming growth factor-β1 (TGFβ1) induced fibrosis. Overexpressing lncRNA-Gm9866 promoted hepatocytes (HCs) apoptosis and the expression of pro-fibrogenic genes, inhibited the proliferation and migration of HCs. Knockdown of lncRNA-Gm9866 inhibited the apoptosis of HCs, the expression of pro-fibrogenic genes, TGFβ1 induced fibrosis and the occurrence of carbon tetrachloride (CCl4)-induced liver fibrosis, and promoted the proliferation and migration of HCs. Mechanistically, lncRNA-Gm9866 may directly bine with Fam98b. Silencing Fam98b in stably overexpressing lncRNA-Gm9866 cell lines reversed the increase of pro-fibrogenic genes and pro-apoptotic genes, fibrosis related pathway protein TGFβ1, Smad2/3, p-Smad2/3 and Notch3 induced by overexpressing lncRNA-Gm9866. Conclusions: LncRNA-Gm9866 may regulate TGFβ/Smad and Notch pathways by targeting Fam98b to regulate liver fibrosis. LncRNA-Gm9866 may be a new target for diagnosis and treatment of liver fibrosis. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) were found to exhibit a remarkable catalytic effect on the decomposition of benzoyl peroxide (BPO) in ethanol at room temperature. The catalytic effects of various carbonaceous materials were investigated by UV spectroscopy. The decomposition reaction for BPO/CNT/ethanol system was studied through gas chromatography-mass spectrometry, infrared spectroscopy and free radical trapping technique. Those results indicated the decomposition of BPO by CNTs occurred via a free-radical pathway involving benzoate radicals. The catalytic mechanism of CNTs was further investigated through electron spin resonance (ESR) spectroscopy and quantum chemical calculations. The ESR signals with same line shape and g -value were found in multi-walled CNTs, single-walled CNTs, and oxidation product of pyrenol. The persistent free radicals (PFRs) on CNTs were essentially aryloxy radicals ([ArO] • ) with spin electrons dispersed on the aromatic plane. Polycyclic aromatic hydrocarbons with larger π-conjugated structures and more aryloxy radicals exhibited a stronger electron-transfer ability. Finally, a three-step pathway for CNTs to decompose BPO was proposed: (1) formation of an asymmetric peroxide (ArO-OOCC 6 H 5) via free radical exchange; (2) conversion of ArO-OOCC 6 H 5 into radicals ([ArO] • and C 6 H 5 COO • ), or ions ([ArO] + C 6 H 5 COO−); (3) formation of benzoic acid by hydrogen or proton abstraction. This study offered tremendous insight into the electronic structures and catalytic mechanism of CNTs, and can facilitated their development for ROS production and scavenging. [Display omitted] [ABSTRACT FROM AUTHOR]

Carbon nanotube (CNT) aqueous suspensions are attracting considerable attention in conductive, antistatic, electromagnetic shielding coatings and films owning to their environmental safety. However, stable CNT suspensions are difficult to prepare because of the remarkable entanglement between CNTs and their intrinsic hydrophobicity. A new class of amphiphilic dispersants—pyrene butyric acid polyethylene glycol monoester (Py-mPEG)—were prepared through the esterification reaction between 1-pyrene butyric acid and polyethylene glycol monomethyl ether. Varieties of multi-walled carbon nanotubes (MWCNTs) aqueous suspensions were prepared by ultrasonic method using the following dispersants: Py-mPEG, sodium dodecyl benzene sulfonate (SDBS), Py-mPEG/Al2O3, and SDBS/Al2O3. The concentrations of suspended MWCNTs were determined by UV–vis absorption spectroscopy, and the state of suspensions was characterized by scanning electron microscopy (SEM). The non-covalent interactions between MWCNTs and Py-mPEG were investigated by fluorescence emission spectroscopy, and density functional theory calculations. The results showed that MWCNTs were more readily dispersed in Py-mPEG solutions than in SDBS solutions, whereas the Al2O3 particles could further improve the dispersion effect. Particularly, the MWCNT concentration reached 1.363 mg/mL using Py-mPEG (1000 ppm)/Al2O3 (particle size: 5–6 µm) as dispersant. A large number of individual MWCNTs were observed from the SEM images of the suspensions. A diffusion experiment on ink showed that the Al2O3 particles with particle size of 5–6 µm were highly responsive to ultrasound. The entangled MWCNTs could be disintegrated by the collision of particles. [ABSTRACT FROM AUTHOR]

In order to study the effect of microcrystalline cellulose on the reaction kinetics of polyurethane, in this work, the multi-scale microcrystalline cellulose was added to the foaming system of multifunctional polyether and multifunctional MDI polyurethane. While the chemical reaction was carried out, it was found through in situ FTIR combined with in situ rheological analysis that what was different from the usual inorganic fillers, the hydroxyl on the surface of the microcrystalline cellulose could preferentially react with MDI to generate urethane under the action of the catalyst. In the initial 5–6 min of the reaction, the reaction of soft segment chain growth was the main reaction. Then the main reaction quickly converted to the cross-linking reaction, which greatly increased the viscosity of the system. The addition of microcrystalline celluloses accelerated the improvement of the cross-linking degree and viscosity of the system. The higher the surface hydroxyl content of microcrystalline cellulose, the more significant this trend become. In addition, although the amount of microcrystalline cellulose added was different, the ratio of the reaction rate of the isocyanate group with the hydroxyl group and the amine group eventually tended to be constant, which indicated that there was a stable reactivity rate in the gradual addition reaction during the cross-linking reaction. Combined with SEM analysis, it was found that 25–60 μm microcrystalline cellulose with large hydroxyl content could act as a nucleating agent when the addition amount was less than 0.1%, which was beneficial to increase the cell density and reduce the pore size and improved the impact performance of the foam. The microcrystalline cellulose with a length of more than 90 μm continuously penetrated through several cell walls and destroyed integrity of the cell structure, which would consequently reduce the impact strength of the foam. This paper provided theoretical guidance for polyurethane modified by microcrystalline cellulose. [ABSTRACT FROM AUTHOR]

Abstract: In this work, a cationic star polymer [poly(2-dimethylamino)ethyl methacrylate (PDMAEMA)] was prepared via atom transfer radical polymerization (ATRP), using brominated calix[4]resorcinarene as an initiator. Hydrophobic moieties, methyl methacrylate (MMA) and butyl acrylate (BA), were further incorporated via “one-pot” method. Well-defined eight-armed star block copolymers bearing hydrophilic blocks inside and hydrophobic blocks outside were synthesized. The molecular weight, particle size, electrophoretic mobility and apparent charge density were determined by gel permeation chromatography (GPC), dynamic light scattering (DLS), phase analysis light scattering (PALS) and colloidal titration, respectively. The zeta potentials and apparent charge densities of the products exhibited the characteristics of polyelectrolyte. The incorporation of hydrophobic moieties generated electrostatic screening effect. The as-synthesized amphiphilic star copolymer is promising as a thermo-sensitive gene carrier for gene therapy. [Copyright &y& Elsevier]

Abstract: To study the rheological properties of long chain branching (LCB) polypropylene (PP), long chain branches (LCB) were grafted onto the linear PP by melt grafting reaction in the presence of a novel chain extender, poly(hexamethylendiamine-guanidine hydrochloride) (PHGH). The branching reactions between the functionalized PP and PHGH were confirmed by transient torque curves and FTIR. By differential scanning calorimetry (DSC) and polarized microscope measurements, the presence of long chain branching structures was further confirmed. Also, the viscoelastic properties of the LCB PP and linear PP under shear flow were investigated for distinguishing LCB PP from linear PP. It was found that the elastic response of LCB PP at low frequencies was significantly enhanced in comparison with that of the linear PP, implying a presence of a long relaxation time mode that was not revealed in linear PP. Moreover, the branching levels of LCB PP were quantified using a detailed method, which was in correspondence with the molar amount of PHGH grafted on PP. [Copyright &y& Elsevier]

Carbon nanotubes (CNTs) could improve the antioxidant properties of polymers because of their radical scavenging activities, but the interaction between CNTs and radicals is ambiguous. We investigated the thermal-oxidative aging resistance of fluorosilicone rubber (FSR) with and without multi-wall carbon nanotubes (MWCNTs), and tracked the concentration of peroxy radicals using chemiluminescence measurements. The results showed that 0.1–0.5 wt% of MWCNTs could block the auto-oxidation degradation of FSR by scavenging the alkyl radicals, thereby showing an antioxidant effect. Based on the structural characterizations of nanocarbons, a set of polycyclic aromatic phenols and polycyclic aryloxy radicals (PArO ·) were constructed and optimized to mimic CNTs. The spin density distribution, spin population, and the formation and reaction of PArO · were calculated using density functional theory (DFT). The results indicated that the CNTs were an open-shell system with a spin density distribution focused on the aryloxy groups and nearby sp2-hybridized carbon atoms. Those atoms with spin populations ranging from 0 to 0.6 a.u. were inert but could react with high-reactivity radicals, including alkyl radicals. This mechanism was confirmed by electron spin resonance measurements of the nanocarbons and heat-treated pyrenols. This study contributed to the development of nanocarbons in antioxidants, catalysts, and reactive oxygen species scavengers. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: It still remains a concern to break through the bottlenecks of anionic polymerization of polar monomers, such as side reactions, low conversion and low temperature (–78°C). In this work, potassium tert‐butoxide (t‐BuOK) was chosen to initiate the anionic polymerization of 2‐ethylhexyl methacrylate (EHMA) in tetrahydrofuran. The conversions were above 99% at 0 or 30°C, and above 95% at 60°C without side reaction inhibitors. The high conversions implied t‐BuOK could suppress the side reactions. A series of block copolymers of EHMA, n‐hexyl methacrylate (HMA) and methyl methacrylate (MMA) were further synthesized at 0°C, and the conversions were all above 99%. The GPC and 1H NMR results confirmed the successful synthesis of the block copolymers. The molecular size of monomer and the state of t‐BuOK (free ion pairs or aggregates) remarkably affected the polymerization rates and the molecular structures of the products. The DMA results indicated that the glass transition temperatures of PEHMA or PHMA block and PMMA block were 20°C and 60°C, respectively, which deviated from –2°C and 105°C of homopolymer, respectively, due to the partial compatibility of the blocks. This work explored a route of the anionic polymerization of polar monomers at room temperature. [ABSTRACT FROM AUTHOR]

In order to break through the bottleneck of anionic polymerization, polar monomers such as methyl methacrylate (MMA), ethyl methacrylate, butyl methacrylate, and hexyl methacrylate are subjected to anionic polymerization at room temperature in tetrahydrofuran (THF) using potassium tert‐butoxide (t‐BuOK) as the initiator. The polymerization of alkyl methacrylates is studied by multidetector gel permeation chromatography, proton nuclear magnetic resonance (1H‐NMR) and 13C‐NMR spectroscopy, and dynamic laser light scattering. It is found that t‐BuOK can initiate the living anionic polymerization of polar alkyl methacrylate, and the polymerization conversion almost reaches up to 100%. t‐BuOK exists into two kinds of agglomerates, whose hydrodynamic volumes are 10 and 80 nm, respectively. t‐BuOK in THF is similar to emulsion and has a critical active species concentration of about 0.0265 mol L−1 and does not depend on how much t‐BuOK is added. After the initiation of the polymerization, the large agglomerates of a loose and less regular structure that have occupied the main part of t‐BuOK are greatly reduced, but they do not continue to decrease until they disappear according to the equilibrium theory. Similarly, the active chain after initiation also will not aggregate again. Furthermore, t‐BuOK also has an active species with smaller average vibration size between cation and anion pairs, which can only initiate the polymerization of MMA with rather slow rate but cannot initiate other alkyl methacrylates. At last, because t‐BuOK can make the dormant species caused by side reactions to be revived, the anionic polymerization of MMA could obtain a high yield. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1130–1139 [ABSTRACT FROM AUTHOR]

Abstract The heat resistance enhancement of fluorosilicone rubber (FSR) can make it more suitable for cutting-edge applications and extreme conditions. This paper focused on the antioxidant properties of boron particles for FSR and the corresponding mechanism. The thermal stability of FSR and FSR/boron composites was characterized by thermal gravimetric analysis (TGA), isothermal degradation and thermal-oxidative ageing. The results showed that boron significantly improved the thermal stability of FSR. In particular, the FSR/boron (100/10) composite retained 95% of its weight after isothermal degradation at 350 °C for 12 h, while the FSR lost 55% of its weight within the initial 1 h. The antioxidant mechanism of boron was further investigated by chemiluminescence (CL), electron paramagnetic resonance (EPR) and vulcanization curves. It was shown that boron has powerful radical scavenging activity (RSA) and inhibited the oxidation scission of the side groups. Moreover, boron revealed no RSA towards the tert-butoxy radical, ensuring the good vulcanization of the FSR/boron composites. Highlights • Boron particles revealed definite enhancement effect due to their strong interactions with the matrix polymer of FSR. • Boron particles could significantly improve the thermal stability of FSR by inhibiting the scission of side groups. • It has been proved boron has powerful radical scavenging activity. • The RSA of boron seems to be selective, and the FSR/boron could be well vulcanized using DBPH as vulcanizer. [ABSTRACT FROM AUTHOR]

Abstract A small addition amount (0.01–4 phr) of multi-walled carbon nanotubes (MWCNTs) were blended into fluorosilicone rubber (FSR) in order to improve its thermal aging properties, and the paper was investigated from three aspects: (1) the distribution of MWCNTs inside FSR was characterized using scanning electron microscope (SEM); (2) the thermal stability of FSR and FSR/MWCNTs was evaluated by the changes of mechanical performance and weight loss in the thermo-oxidative aging process, and the function mechanism of MWCNTs was studied by thermogravimetric analysis (TGA), chemiluminescence (CL), electron spin resonance (ESR) and fourier transform infrared spectroscopy (FTIR) measurements; (3) the vulcanization properties of FSR and FSR/MWCNTs were obtained from their vulcanization curves employing three kinds of peroxides as vulcanizers. The results showed MWCNTs, with a homogeneous distribution inside FSR, had significantly improved the antioxidant performance of FSR due to their powerful radical scavenging activity. Moreover, MWCNTs revealed no scavenging effect on the tert -butoxy radical, which ensured that FSR/MWCNTs could be well vulcanized. Highlights • A small addition amount (0.01–4 phr) of MWCNTs has significantly improved the thermal stability of fluorosilicone rubber. • The antioxidant property of MWCNTs is attributed to their powerful radical scavenging activity. • MWCNTs exhibit a high selectivity for scavenging different radicals. • As a great antioxidant, MWCNTs can improve the thermal stability of elastomers without negative effects on their vulcanization. [ABSTRACT FROM AUTHOR]

Antimicrobial cotton fabrics received much attention for the demand of health and hygiene fields. In this work, an antimicrobial copolymer was prepared via a reaction between polyhexamethylene guanidine hydrochloride and polypropylene glycol diglycidyl ether. The copolymer has amphiphilic characteristic and excellent antimicrobial properties. When the copolymer was adhered onto cotton fabrics through physical adsorption and chemical bonding using dipping-drying method, the resultant cotton fabrics had excellent and durable antimicrobial properties. The antimicrobial rates against Escherichia coli and Staphylococcus aureus were higher than 99.99% when the adsorption amount of the copolymer was above 35.5 mg/g. The antimicrobial cotton fabrics remained the excellent antimicrobial properties even after laundered with detergent solution. [ABSTRACT FROM AUTHOR]

[Display omitted] • In vitro synthesis of melanin with blue light blocking properties. • In favor of the radical–radical coupling mechanism on indole polymerization. • Cyclic oligomers of indole derivatives were identified in the polymerization. Blue light hazards have garnered increasing attention owing to the popularity of displays. Although melanin on the retina acts as a blue light barrier, overexposure to blue light increases the risk of visual damage. A class of methyl indole- n -carboxylate oligomers (O-MI n C, n = 3, 4, 5, 6, and 7) was synthesized through solid-phase oxidative polymerization. Based on the experimental characterizations, including time-of-flight mass spectrometry, infrared spectroscopy, and density functional theory calculations of the average local ionization energy, we proposed a mechanism for the oxidative polymerization of methyl indole-4-carboxylate (MI4C). Methyl indole-4-carboxylate oligomer (O-MI4C) is composed of cyclic oligomers containing large conjugated structures that are generated by the repetition of electron deprivation, radical coupling, and dehydrogenation reactions. O-MI4C exhibits the best blue light absorption among its allotropes substituted at different positions with a cut-off absorption wavelength of 530 nm. Finally, O-MI4C was added to polymethylmethacrylate (PMMA) and Columbia resin 39 (CR-39) flakes through in situ polymerization to investigate the behavior of blue light blocking. The PMMA/O-MI4C (0.01 wt%) and CR-39/O-MI4C (0.02 wt%) can block 25% and 35% of blue light; however, they have no significant effect on green and orange lights. [ABSTRACT FROM AUTHOR]

This study investigated the relationship between the extensional rheological behaviors and the foamability of polypropylenes (PPs). Both the shear and extensional rheological properties of four types of PPs with different molecular structures (linear PP, linear PP with high-molecular component, long-chain-branched PP, and cross-linked PP) were tested by rheometers and the PPs were foamed by batch process with supercritical carbon dioxide as foam agent. It was found that when the PP showed strain-hardening behavior at certain strain rates (on the order of 1 s−1), the obtained foams had high expansion ratio and fine cell structures. Otherwise, the strain-hardening behavior of PP had limited effects on the foamability. In addition, a theoretical analysis suggested that the strain-hardening behavior provided higher melt strength and simultaneously changed the rupture behavior of the melt, thus the gas bubble could be stable during expansion step and the cellular structure was generated. The foamability of PPs can be predicted from the extensional properties without considering their molecular structures. [ABSTRACT FROM AUTHOR]

This work confirms the new view of the initiation and propagation mechanism of the anionic polymerization previously proposed, based on the investigation of anionic bulk-polymerization of styrene and α-methyl styrene with the help of a self designed microflow device and characterized by GPC and in situ 7Li NMR. It was found that n-BuLi tended to form the hexameric-aggregated structure and even to form the huge aggregated structure based on the former. These aggregations of initiators could directly initiate the anionic polymerization and form the supramolecule aggregations. The supramolecule aggregations inevitably blocked the diffusion of the monomers to the ion-pairs and resulted in a stationary-conversion platform. Then the aggregators were dissociated completely into equal binary-aggregated species, and the polymerization continued again rapidly before the termination. Tetrahydrofuran (THF) acted as the electron donator, which could push the electron cloud to Li cation and make the aggregated ring of the active species rather loosened and facilitated the monomer to insert in. Therefore, a little THF can greatly promote the anionic polymerization. However, further addition of THF might block the channel between the ion-pairs and decrease the propagation rate. It was also found that the aggregated structure of the active species during the anionic polymerization only depends on the initiator aggregations which were formed before the polymerization. [ABSTRACT FROM AUTHOR]

The comb-like ionenes with aliphatic side chains were prepared and blended with a low density polyethylene (LDPE) for enhancing the antistatic and antimicrobial properties. The resulting blends were well characterized, particularly based on the surface resistivity (ρ) which revealed the antistatic properties of LDPE/ionene blends. The results showed that the values of ρ decreased 1-5 orders of magnitude after the ionenes were added. Various influencing factors on ρ, including ionene structures, ionene content, and humidity were investigated in detail. Furthermore, the surface and inner structures of resulting blends were characterized by ATR-FTIR and SEM along with water contact angle measurements. The antimicrobial activities of the ionenes and the blended sheets were assessed based on the minimal inhibitory concentration (MIC) values against E. coli and the growth inhibition of E. coli determined by means of a membrane adhering-colony counting method. The results indicated that the ionene with 4-carbon side chains had the lowest MIC value (7.8 μg/mL) and the corresponding blend reached 99.9 % of growth inhibition. [ABSTRACT FROM AUTHOR]

Abstract: A novel strategy for introducing long chain branches (LCB) on commercial polypropylene (PP) was described using an extender agent, poly (hexamethylendiamine-guanidine hydrochloride) (PHGH), to couple with glycidyl methacrylate-grafted PP (PP-GMA). The presence of LCB was confirmed by GPC and melt strength measurements in two modified PP samples, MPP-1 and MPP-2. The foamability of LCB PPs and commercially linear PP (EPS) was investigated by foam extrudate. The results showed that the foamability of LCB PPs was significantly improved. To find out the difference in foamability of EPS and LCB PPs, some rheological properties were investigated. In the dynamic shear measurement, it was found that the elastic response of LCB PPs at low frequencies was distinctly enhanced in comparison with that of EPS, implying a presence of a long relaxation time mode that was not revealed in linear PP. The elongational rheology results showed that the strain hardening behaviors of LCB PPs were still intense even at higher strain rate of 1s−1; moreover, MPP-2 could sustain larger elongational stress and deformation, which helps to improve the foamability. In step-shear stress relaxation measurements, the fast and slow relaxation processes were observed over the entire ranges of strains, indicating the presence of two different relaxation time modes. Also, the strain dependence of slow damping function became weaker because of the introduction of LCB on linear PP. In addition, it was also found that the rheological behaviors characterizing the long relaxation time mode were further enhanced with the increase of the concentration of PHGH in the melt grafting reactions. [Copyright &y& Elsevier]

• PHMG was used as chain extender to synthesize antimicrobial spandex spinning resin. • Composite spandex (CS) with antimicrobial activity was obtained by dry spinning. • CS exhibited intrinsic, rapid and excellent antimicrobial activities. • The overall performances of CS were better than ordinary spandex. Polyhexamethylene guanidine hydrochloride (PHMG) was used as a functional "gene" to replace the diamine in ordinary spandex, and a "gene reconstruction" spandex (GRS) spinning solution was synthesized. Mixing a small amount of GRS spinning solution with ordinary spandex spinning solution, composite spandex (CS) with intrinsic antimicrobial activity was obtained by a dry-spinning process under a normal spinning condition. The TEM results indicated that PHMG in the GRS molecular chain was uniformly distributed in CS in a granular shape with 10–100 nm diameter and was aligned along the fiber axial direction with a chain-like structure. The inhibition rates of CS (containing 0.5 wt% PHMG) against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) exceeded 99.99%. CS maintained excellent antibacterial properties after soaking in acetic acid solution at pH 3 for 45 min at 95 °C and showed strong intrinsic antimicrobial characteristics. Confocal laser scanning microscopy demonstrated that bacteria was quickly adsorbed on the surface of CS fiber, the cell membrane was damaged, and gradually bacteria died. The molecular simulation indicated that the positive charges accumulated on the PHMG surface, providing the driving force to attract bacteria with negative charge on the cell membrane phospholipid layer. TGA, DSC, XRD and mechanical property analysis confirmed that the corresponding performances of CS were better than those of ordinary spandex without GRS. In summary, the as-prepared CS by "gene reconstruction" eliminated the exudation problem of antibacterial agents in the traditional antimicrobial materials. [ABSTRACT FROM AUTHOR]

• The Trommsdorff effect was weakened and postponed under higher shear rate. • Increasing shear rate significantly enhanced the chain initiation rate(R i) • The Trommsdorff effect occurred at a critical viscosity about 1000 ± 100 Pa·s. • The Trommsdorff effect was effectively utilized during reactive extrusion of PMMA. In this study, a concentric-cylinder and double-walled reactor accurately controlling shear rates was established to conduct the free radical bulk polymerization of methyl methacrylate, and the kinetics of Trommsdorff effect under constant shear was investigated. The results showed that increasing shear rate significantly enhanced the termination rate constant (k t), and thus effectively weakened and postponed the Trommsdorff effect. However, the polymerization rate during the "quasi-steady state" was almost not affected by shear rate. Differing from the classical theory, the chain initiation rate (R i) also increased with shear rate, which was due to the improving initiation efficiency of polymerization reaction. On the other hand, it was found that the critical viscosity when Trommsdorff effect occurred was about 1000 ± 100 Pa·s, independent of shear rates, temperatures and initiator concentrations. Based on utilizing the Trommsdorff effect, polymethyl methacrylate (PMMA) was further synthesized via reactive extrusion, with superior performance comparing to commercial product. [ABSTRACT FROM AUTHOR]

Initiating Mechanism of the Anionic Polymerization of Methacrylates with t-BuOK and the Synthesis of ABA Type Triblock Copolymers B Back Cover b : In article number 1900390, Anna Zheng, Yong Guan, and co-workers report that using I t i -BuOK as initiator, an ABA-type triblock copolymer (PMMA-b-PLMA-b-PMMA) is synthesized at 0 °C without using any sidereaction inhibitors and the monomer conversion is over 97%, which paves the way for the synthesis of thermoplastic elastomers with full polar monomers and full saturated chains by anionic polymerization. [Extracted from the article]

Using potassium tert‐butoxide (t‐BuOK) as initiator, anionic polymerization and copolymerization of the methacrylate monomers are carried out in tetrahydrofuran at 0 °C or above. The polymers are characterized by gel permeation chromatography (GPC), proton nuclear magnetic resonance (1H‐NMR), Fourier transform infrared (FTIR), and dynamic mechanical analyzer (DMA). There is a critical concentration of the active species in t‐BuOK, above which no matter how much more t‐BuOK is added, it has no initiation activity. Among the active species of t‐BuOK, the main part possesses large average vibration distance between anion–cation pairs, which can initiate all methacrylate monomers in this study. While another part of the active species possesses the small average vibration distance, which can only initiate the polymerization of methyl methacrylate at slow rate. It provides an supporting evidence for the "channel idea" proposed previously. Finally, poly(methyl methacrylate)‐b‐poly(lauryl methacrylate)‐b‐poly(methyl methacrylate) (PMMA‐b‐PLMA‐b‐PMMA) three‐block copolymer is synthesized. This study paves the way for the synthesis of thermoplastic elastomers with full polar monomers and full saturated chains by anionic polymerization. [ABSTRACT FROM AUTHOR]