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Background Locally advanced pancreatic cancer (LAPC) remains a challenge for current treatments. Local destructive therapies, such as irreversible electroporation (IRE) and radiofrequency ablation (RFA), were used more and more frequently in the treatment of LAPC. Objective This study aimed to compare the efficacy of IRE with RFA in patients with LAPC. Methods From August 2015 to August 2017, 58 LAPC patients after IRE or RFA therapy, which was performed through open approach, were retrospectively reviewed. The survival outcomes after IRE (36 patients) and RFA (18 patients) were compared after propensity score matching (PSM) analysis. Results Before PSM analysis, IRE after the induction chemotherapy resulted in significant higher overall survival (OS) rates and progression‐free survival (PFS) rates to RFA (2‐year OS, 53.5% vs 30.8%, P = .013; 2‐year PFS, 28.4% vs 12.1%, P = .043). After PSM analysis, compared with RFA, the survival benefit of IRE was even more obvious, (2‐year OS, 53.5% vs 27.0%, P = .010; 2‐year PFS, 28.4% vs 6.4%, P = .018). For patients with tumor larger than 4 cm, IRE resulted in comparable OS and PFS between RFA and IRE while IRE also achieved better long‐term OS to RFA for those with tumor smaller than 4 cm. Multivariate analysis illustrated that IRE was a favorable prognostic factor in terms of OS and PFS in patients with LAPC. Conclusions IRE after induction chemotherapy is superior to RFA after induction chemotherapy for treating LAPC patients while these two therapies have comparable efficacy for tumors which were larger than 4 cm., Locally advanced pancreatic cancer (LAPC) is a devastating disease while the standard chemotherapy remains an unmet need in the management of LAPC. Only a multidisciplinary approach can be effective in obtaining both a local tumor reduction and a systemic control of disease. Local destructive therapies were important components of the multidisciplinary treatment. Radiofrequency ablation (RFA) and irreversible electroporation (IRE) have been proposed as new treatment options in the multimodal treatment of the LAPC. Until recently, there is a lack of studies comparing treatment effects between IRE and RFA. Therefore, we aimed to investigate the effect of IRE versus RFA after the induction chemotherapy on long‐term OS and progression‐free survival (PFS) in patents with LAPC. It was the first time to show that IRE resulted in better OS and PFS than RFA after the induction chemotherapy in patients with LAPC and should be considered as the first‐line ablation modality. A new ablative method, RFA ablation followed by tumor margin accentuation by IRE, is also considerable.

Background To investigate whether the relative computed tomography (CT) value (rCT) of adjacent pancreatic parenchyma can distinguish focal‐type autoimmune pancreatitis (fAIP) from pancreatic ductal adenocarcinoma (PDAC). Methods A total of 13 patients with fAIP and 20 patients with PDAC were included in this study. The rCT was calculated as the ratio of the CT value of adjacent pancreatic parenchyma to that of muscle. The diagnostic performance of rCT for discriminating fAIP from PDAC was evaluated using receiver operating characteristic (ROC) analysis. Results Both fAIP and PDAC presented hyper‐fibrosis histologically and delayed enhancement on CT examination. Moreover, the pancreatic parenchyma of fAIP presented serious inflammation. The mean rCT of the parenchyma was significantly lower in fAIP than in PDAC in all phases. The best diagnostic performance of the rCT value was found in the pancreatic phase, with an area under the ROC curve of 0.912, while the areas under the ROC curve of the portal and delayed phases were 0.812 and 0.754, respectively. The optimal cut‐off value for distinguishing fAIP from PDAC was 1.62 in the pancreatic phase. Conclusions The rCT of the pancreatic parenchyma during the pancreatic phase may be a feasible CT feature for differentiating fAIP from PDAC., Similar imaging features such as regional enlargement of the pancreas and delayed enhancement became a big challenge to differentiate focal‐type autoimmune pancreatitis (fAIP) from PDAC. In this study, we found that the pancreatic parenchyma of fAIP presented severe inflammation. Moreover, the mean relative computed tomography values of the pancreatic parenchyma were lower in fAIP than that in PDAC in all phases.

Background Cancer‐associated fibroblasts (CAFs) are among the most prominent cells during the desmoplastic reaction in pancreatic ductal adenocarcinoma (PDAC). However, CAFs are heterogeneous and the precise origins are not fully elucidated. This study aimed to explore whether monocytes can transdifferentiate into fibroblasts in PDAC and evaluate the clinical significance of this event. Methods CD14+ monocytes were freshly isolated from human peripheral blood. Immunofluorescence, reverse transcription‐quantitative PCR, western blot, flow cytometry and enzyme‐linked immunosorbent assay were used to detect the expression of αSMA, fibronectin, and other relevant molecules. In addition, latex beads with a mean particle size of 2.0 µm were used to assess the phagocytic capacity. Moreover, RNA sequencing (RNA‐seq) was performed to identify the differences induced by H2O2 and the underlying mechanisms. Results Immunofluorescence identified αSMA and fibroblast‐specific protein 1 expression by tumor‐associated macrophages in PDAC. The in vitro experiment revealed that oxidative stress (H2O2 or radiation) induced monocyte‐to‐myofibroblast transdifferentiation (MMT), as identified by upregulated αSMA expression at both the RNA and protein levels. In addition, compared with freshly isolated monocytes, human monocyte‐derived macrophages increased fibronectin expression. RNA‐seq analysis identified p53 activation and other signatures accompanying this transdifferentiation; however, the p53 stabilizer nutlin‐3 induced αSMA expression through reactive oxygen species generation but not through the p53 transcription/mitochondria‐dependent pathway, whereas the p38 inhibitor SB203580 could partially inhibit αSMA expression. Finally, MMT produced a unique subset of CAFs with reduced phagocytic capacity that could promote the proliferation of pancreatic cancer cells. Conclusions Oxidative stress in the tumor microenvironment could induce MMT in PDAC, thus inducing reactive stroma, modulating immunosuppression, and promoting tumor progression. Reducing oxidative stress may be a promising future therapeutic regimen., Monocytes in human blood are recruited into PDAC tissues. Low intracellular levels of H2O2 are important for fibronectin mRNA synthesis, protein expression and secretion. Oxidative stress can reduce the phagocytic capacity and simultaneously activate the p38‐MAPK signaling pathway, thus inducing αSMA mRNA and protein expression (monocyte‐to‐myofibroblast transdifferentiation). However, these cells do not express Col1. In addition, supernatant from these cells can stimulate pancreatic cancer cell (AsPC‐1) proliferation.

Background Irreversible electroporation is shown to induce immune changes in pancreatic cancer while the histology evidences are still lacking. The aim of this study is to show the immune changes in histology and explore whether irreversible electroporation (IRE) can induce immunogenic cell death (ICD) of tumor cells and activate specific immune responses. Methods Subcutaneous and orthotopic pancreatic cancer models were established and used to evaluate the effect of immune modulation of IRE. The infiltration of T cells was assessed in several tissue samples before and after IRE. Abscopal effect was then assessed by comparing the tumor growth of subcutaneous tumors after in situ ablation with IRE or exposure to tumor culture supernatant (TSN) of IRE‐treated Pan02. The expression of damage‐associated molecular patterns (DAMPs) of tumor cells after IRE was detected in vitro. Results IRE could significantly suppress the tumor growth and increase the infiltration of CD8+ T cells. After ablation with IRE or stimulation with TSN of Pan02 treated by IRE, the growth of untreated tumor was suppressed and the effector CD8+ T cells and memory T cells increased significantly in mice. Additionally, the inhibition effect of tumor growth increased along with the increasing strength levels of electroporation. IRE induced ICD of tumor cells by increasing the synthesis and secretion of DAMPs. Conclusions IRE induced local immunomodulation by increasing specific T cells infiltration. Through enhancing specific immune memory, IRE not only led a complete tumor regression in suit, but also induced abscopal effect, suppressing the growth of the latent lesions.

A highly emissive microgel is synthesized by polymerizing tetraphenylethene (TPE) based comonomers, acrylic acid, NIPAM, and permanent crosslinker ethylenebisacrylamide (BIS) (named as TPE microgel), which exhibited temperature responsive fluorescence emission. Rhodamine B (RhB), a positively charged molecule, is then inserted onto the surface of fabricated microgels through electrostatic interaction. As a result, a novel artificial light harvesting system with high energy transfer efficiency is constructed (named as TPE microgel-RhB light harvesting system), which is the first light harvesting system based on TPE microgels presenting dual response to pH and temperature. MTT assay indicates the fabricated TPE microgel and TPE microgel-RhB light harvesting system has good cytocompatibility. The strong fluorescence and good cytocompatibility make them perfect candidates for cell imaging. The prepared emissive microgel and light-harvesting system with desirable fluorescent property not only provide a new strategy for the fabrication of tunable luminescent nanomaterials, but also expand potential applications in the fields of stomach recognition, temperature sensors, and drug delivery.

Chemically cross-linked SixOy cage clusters embedded in N-doped carbon are prepared by thermal treatment of octa-ammonium polyhedral oligomeric silsesquioxane in an inert environment. Transmission electron microscopic studies show that by annealing at 900 °C, Si-rich clusters with size of ~ 5 nm are formed and uniformly distributed in a lighter matrix. XPS analysis indicates that the sample obtained from annealing at 900 °C (P900) has chemical composition of Si6.5O12.0C9.3N0.5, and in addition to Si-O bonds, it also contains substantial amounts of Si-C, C-O bonds and sp2 C, as well as a small amount of C=N bonds. This, together with TGA analysis, suggests that the clusters are likely to be formed by chemical cross-linking several POSS cages through Si-C or C-O bonds, while the matrix may be N-doped carbon resulted from carbonization of some detached side chains. When used as a lithium-ion battery anode, P900 exhibits stable and high cycled and rate capacity. The cycled capacity can last for at least 1000 cycles. These are much better than the anodes made from silicon oxides, which could be ascribed to, firstly, the less compact yet fairly stable Si-O active sites brought by the cage structure and the cross-linking; secondly, the small size of the clusters that ensures smooth and complete lithium insertion/extraction, and finally, the "island-in-sea" morphology for the clusters-in-carbon hybrid that enhances interfacial interactions and facilitates charge conduction

A novel hard disk lubricant IDL2 was synthesised by reacting sodium 4-((2,2-dimethyl-1,3-dioxolan-4-yl)methoxy)phenoate with hexachlorocyclotriphosphazene, followed by treatment with 1H,1H-perfluoro-3,6,9-trioxatridecan-1-ol in the presence of sodium hydride and subsequent hydrolysis using sulfuric acid. The chemical structure of IDL2 was confirmed by proton nuclear magnetic resonance (1H NMR), phosphorus-31 (31P) NMR spectroscopy and mass spectrometer. The thermal property of IDL2 was analysed using thermal gravimetric analysis (TGA) and it shows better thermal stability than two commercial lubricants Z-DOL and Z-Tetraol with two and four terminal hydroxy groups, respectively. IDL2 was found to have comparable hydrophobicity to commercial lubricants Z-DOL, A20H and Z-Tetraol with water contact angles in the range of 78 – 85°, revealing that IDL2 has analogous surface energy to these commercial lubricants. IDL2 exhibits comparable friction coefficient to A20H and Z-Tetraol, but much lower than Z-DOL. More interestingly, it has a much high bonding ratio when compared with commonly used commercial lubricants under the same testing conditions due to the presence of two polar hydroxy groups, which enhance the interaction between lubricant and substrate. These promising properties of IDL2 show that it would be very potential for real application as a hard disk drive lubricant. Copyright © 2016 John Wiley & Sons, Ltd.

The effect of residual N,N′-dimethylformamide (DMF) on curing behavior and mechanical properties of neat epoxy and lignin epoxy composites is studied. The significant enhancement in their mechanical properties is found to be induced by residual DMF for the first time. The spectra and mechanical analysis indicates that the entrapped DMF is likely to decompose at high temperature to yield dimethylamine, which should act like excess amine and take part in the formation of network structure, lower the crosslink density, increase the chain packing, improve the Van der Waal's interaction, and eventually enhance their mechanical performances. Lignin epoxy composites prepared with the aid of tetrahydrofuran or DMF show significant difference in their mechanical properties. It is therefore important to distinguish the filler effect from the solvent effect when a solvent is used in epoxy composites preparation.

Coacervation is a process during which a homogeneous aqueous solution undergoes liquid-liquid phase separation, giving rise to two immiscible liquid phases composed of a colloid-rich coacervate phase in equilibrium with a colloid-poor phase simultaneously. Recent attempts to develop complex coacervation from macromolecular self-assemblies have diversified a large group of novel coacervate-related materials with sophisticated properties and emerging applications. In this review, the most recent progress in the design strategies of macromolecular complex coacervation is discussed with respect to different key parameters, including macromolecular structure, mixing ratio, ionic strength, pH, and temperature, etc. Furthermore, the applications of these multiple-functional coacervate materials, oriented toward advanced encapsulation, are further summarized into several active domains in wastewater treatment, protein purification, food formulation, underwater adhesives, drug delivery, and cellular mimics. Finally, perspectives and future challenges related to the further advancement of macromolecular complex coacervates are proposed.

Emission of conjugated polymers is known to undergo bathochromic shift from solution to film formation due to π-π stacking in the solid state. In this report, a series of pearl-necklace-like hybrid polymers is designed via the hydrosilylation condensation between bifunctional polyhedral oligomeric silsesquioxanes (B-POSS) and oligofluorene segments. Optoelectronic analyses unequivocally show that the presence of these interconnecting B-POSS can effectively reduce red-shift in photoluminescence and electroluminescence during film formation. These hybrid poly(oligofluorenes) display stable blue emission with high color purity. Thermal analyses also indicate that they are vitrified polymers with high glass transition temperature (up to 125 °C). We believe that this strategy can be extended to other conjugated systems to control color purity in electroactive materials and holds promise as new emissive materials for various applications.

Poly(N-isopropylacrylamide)-block-poly(l-lactic acid)-block-poly(N-isopropylacrylamide) (PNIPAAM-b-PLLA-b-PNIPAAM) and PNIPAAM-b-PDLA-b-PNIPAAM triblock copolymers with varying polylactic acid (PLA) lengths are synthesized using a combination of ring-opening polymerization and atom-transfer radical polymerization. Results of (1) H NMR and gel permeation chromatography analyses show that the copolymers have a well-defined triblock structure and the PLA segment lengths can be readily controlled with monomer feed ratio. Stereocomplexation between the enantiomeric PLA segments is confirmed with differential scanning calorimetry and wide-angle X-ray scattering. Dynamic light scattering experiments show that (1) the LCST of PNIPAAM in water could be tailored from 32 °C up to 38.5 °C by increasing the length of PLA segments and mixing copolymers of similar molecular weight with enantiomeric PLA segments to induce stereocomplexation, and (2) the LCST of each mixed copolymer system could be tailored within a 2-3 °C range of body temperature by manipulating the ratio of the enantiomeric copolymers in solution.

We report the effect of filler modification on the properties of polylactide (PLA)-based nanocomposites, where graphene oxide (GO) nanosheets and polyhedral oligomeric silsesquioxane (POSS) nanocages are employed as nanofillers. The organically treated nanofillers are termed as GO-functionalized and POSS-functionalized. The synthesis of the nanocomposites was carried out via in situ ring-opening polymerization of lactic acid (LA). The following four naocomposite systems were prepared, characterized, and compared to achieve a better understanding of structure-property relationship (1) PLA/GO-functionalized, (2) PLA/POSS-functionalized, (3) PLA/physical mixture of GO-functionalized and POSS-functionalized, and (4) PLA/GO-graft-POSS (with eight hydroxyl groups). As revealed by the thermal and mechanical (nanoindendation) characterization, that the nanocomposites having a combination of GO and POSS as nanofiller, either as physical mixture of GO-functionalized and POSS-functionalized or as GO-graft-POSS, is far more superior as compared with the nanocomposites having individually dispersed nanofillers in the PLA matrix. Observed enhancement is attributing to the synergistic effect of the nanofillers as well as better dispersion of the modified-fillers in the matrix. POLYM. COMPOS., 35:118–126, 2014. © 2013 Society of Plastics Engineers

Novel temperature and pH dual-responsive dendritic polyoligomeric silsesquioxane (POSS)–poly(N-isopropylacrylamide) (PNIPAm)–poly(2-hydroxyethyl methacrylate) (PHEMA) copolymers are prepared via atom transfer radical polymerization and click reactions. The cloud points (Tc) decrease with decreasing pH from 10.0 to 5.0 due to the weakened inter-molecular interactions and enhanced intra-molecular hydrogen bonding, whereas the Tc exhibits a small increase from pH 5.0 to 4.0 because of the better solvation of PHEMA at highly acidic conditions. The above findings are corroborated by the different sizes of aggregates observed by dynamic light scattering. The encapsulation of a fluorescent dye and stimulated release by temperature and pH changes are also demonstrated.

This report describes a new route to covalently bonded polymer–graphene nanocomposites and the subsequent enhancement in thermal and mechanical properties of the resultant nanocomposites. At first, the graphite is oxidized by the modified Hummers method followed by functionalization with Octadecylamine (ODA). The ODA functionalized graphite oxides are reacted with methacryloyl chloride to incorporate polymerizable CC functionality at the nanographene platelet surfaces, which were subsequently employed in in situ polymerization of methylmethacrylate to obtain covalently bonded poly(methyl methacrylate) (PMMA)–graphene nanocomposites. The obtained nanocomposites show significant enhancement in thermal and mechanical properties compared with neat PMMA. Thus, even with 0.5 wt % graphene nanosheets, the Tg increased from 119 °C for neat PMMA to 131 °C for PMMA–graphene nanocomposite, and the respective storage modulus increased from 1.29 to 2 GPa. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4262–4267, 2010

Chemical reactions under microwave irradiation can be very efficient, with a significant shortening of reaction time. Few studies have reported the use of microwaves to functionalize carbon nanotubes. In the work reported, a new method of formulating functionalized multi-walled carbon nanotubes (MWNTs) was developed by covalent grafting of polyamide 6 (PA6) chains onto the carbon nanotubes assisted by microwave irradiation. PA6 chains were grafted onto acidified MWNTs through condensation reaction between the carboxylic groups of the MWNTs and the terminal amine groups of PA6 using microwave radiation heating. The functionalized carbon nanotubes (MWNT-g-PA6) were characterized systematically using infrared and Raman spectroscopy, transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). TEM showed that the surface of the MWNTs was covered with a layer of PA6. TGA results indicated that the MWNT-g-PA6 contained about 47 wt% of polymer. A novel, convenient and efficient functionalization approach is reported, involving covalently grafting PA6 chains onto MWNTs assisted by microwave irradiation. Copyright © 2010 Society of Chemical Industry

Strength and toughness are the two most important prerequisites for structural applications. Unfortunately, these two properties are often in conflict in materials. Here, an effective and yet practical strategy is proposed to simultaneously strengthen and toughen poly(l-lactide) (PLLA) using a simple rigid-rubber "reinforcing element." This element consists of a rigid graphene oxide (GO) sheet covalently coupled with poly(caprolactone-co-lactide) (PCLLA) rubbery layers, which can be easily synthesized and incorporated into PLLA matrix to develop composites with well-tailored GO/PLLA interfaces. It is demonstrated that by adding the "reinforcing element," i.e., GO-graft-rubber-graft-polyd-lactide), PLLA exhibits higher strength and higher toughness, which could be attributed to the synergy of rigid GO and rubbery PCLLA working in tandem during deformation. It is further demonstrated that this strategy can also be applied to other filler systems, such as clay and particulate polyhedral oligomeric silsesquioxane, and other polymer systems, such as poly(methyl methacrylate). The strategy could be considered as a general design principle for reinforcing materials where both strength and toughness are the key concerns. ASTAR (Agency for Sci., Tech. and Research, S’pore)

The synthesis, micelle formation, and bulk properties of semifluorinated amphiphilic poly(ethylene glycol)-b-poly-(pentafluorostyrene)-g-cubic polyhedral oligomeric silsesquioxane (PEG-b-PPFS-g-POSS) hybrid copolymers is reported. The synthesis of amphiphilic PEG-b-PPFS block copolymers are achieved using atom transfer radical polymerization (ATRP) at 100 degrees C in trifluorotoluene using modified poly(ethylene glycol) as a macroinitiator. Subsequently, a proportion of the reactive para-F functionality on the pentafluorostyrene units was replaced with aminopropylisobutyl POSS through aromatic nucleophilic substitution reactions. The products were fully characterized by H-1-NMR and GPC. The products, PEG-b-PPFS and PEG-b-PPFS-g-POSS, were subsequently self-assembled in aqueous solutions to form micellar structures. The critical micelle concentrations (cmc) were estimated using two different techniques: fluorescence spectroscopy and dynamic light scattering (DLS). The cmc was found to decrease concomitantly with the number of POSS particles grafted per copolymer chain. The hydrodynamic particle sizes (R-h) of the micelles, calculated from DLS data, increase as the number of POSS molecules grafted per copolymer chain increases. For example, Rh increased from similar to 60 nm for PEG-b-PPFS to similar to 80 nm for PEG-b-PPFS-g-POSS25 (25 is the average number of POSS particles grafted copolymer chain). Static light scattering (SLS) data confirm that the formation of larger micelles by higher POSS containing copolymers results from higher aggregation numbers (N-agg), caused by increased hydrophobicity. The R-g/R-h values, where R-g is the radius of gyration calculated from SLS data, are consistent with a spherical particle model having a core-shell structure. Thermal characterization by differential scanning calorimetry (DSC) reveals that the grafted POSS acts as a plasticizer; the glass transition temperature (T-g) of the PPFS block in the copolymer decreases significantly with increasing POSS content. Finally, the rhombohedral crystal structure of POSS in PEG-b-PPFS-g-POSS was verified by wide angle X-ray diffraction measurements. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 152-163, 2010

Hyperbranched organic–inorganic hybrid conjugated polymers P1 and P2 were prepared via FeCl3-oxiditive polymerization of 4,7-bis(3-ethylhexyl-2-thienyl)-2,1,3-benzothiadiazole (A) and octa(3-ethylhexyl-2-thienyl-phenyl)polyhedral oligomeric silsesquioxane (POSS) (B) at different POSS concentrations. Compared to linear polymer PM derived from A, P1, and P2 exhibit much higher PL quantum efficiency (ϕPL-f) in condensed state with improved thermal stability. ϕPL-f of P1 and P2 increased by 80% and 400%, and the thermal degradation temperatures of P1 and P2 are increased by 35 °C and 46 °C, respectively. Light-emitting diodes were fabricated using P1, P2, and PM. While the electroluminescent spectra of both P1 and PM show λmax at 660 nm, P1 exhibits a much narrower EL spectrum and higher electroluminescence (∼500%) compared with PM at a same voltage and film thickness. The maximum current efficiency of P1 is more than seven times of that of PM. The turn-on voltages of the LEDs are in the order of P2 > PM > P1. LED prepared by blending P1 with MEH-PPV shows a maximum luminescence of 2.6 × 103 cd/m2 and a current efficiency of 1.40 cd/A, which are more than twice (1.1 × 103 cd/m2) and five times (0.27 cd/A) of LED of PM/MEH-PPV blend, respectively. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5661–5670, 2009

Star-like polyurethane (PU) hybrid films containing octafunctional cubic silsesquioxanes are prepared by polyaddition reaction between octakis(dimethylsilyloxy) silsesquioxane isopropenyldimethylbenzyl isocyanate (OS-PDBI) and octakis(dimethylsilyloxy) hydroxypropyl silsesquioxane (HPS); and between OS-PDBI and hexane diol (HD). The effect of incorporation of nanostructured cubic silsesquioxanes (CSSQ) on the macroscopic properties of PU film and their thermomechanical properties are investigated. The obtained hybrid films are relatively transparent. Their morphologies and properties are studied by using Fourier transform infra-red spectroscopy (FTIR), X-ray diffraction (XRD), atomic force microscopy (AFM), thermogravimetry (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and contact angle measurements. The formation of urethane linkage disrupts the three-dimensional ordered structure of CSSQ in the hybrid film. AFM images show clearly that no phase separation in the macroscopic level for both PU hybrid films. TGA and DMA analyzes indicate that the incorporation of octafunctional silsesquioxane in PU hybrid film provides enhanced thermal stability and increased crosslink density. Moreover, the existence of cage structure also improves oxidation resistance and mechanical strength. The incomplete reaction between OS-PDBI and HPS due to the steric hindrance of highly branched rigid CSSQ could result in a slight decrease in initial decomposition temperature. Furthermore, hardness and out-of-plane compressive modulus are also investigated by nanoindentation.

Nylon 11 (PA11) nanocomposites with different loadings of multi-walled carbon nanotubes (MWNTs) were prepared by melt compounding. Scanning electron microscopy images on the fracture surfaces of the composites showed a uniform dispersion of MWNTs throughout the matrix. The presence of the MWNTs significantly improved the thermal stability and enhanced the storage modulus (G′) of the polymer matrix. Melt rheology studies showed that, compared with neat PA11, the incorporation of MWNT into the matrix resulted in higher complex viscosities (|η*|), storage modulus (G′), loss modulus (G″), and lower loss factor (tanδ). PA11 and its nanocomposites containing less than 1 wt% MWNTs showed similar frequency dependencies and reached a Newtonian plateau at low frequencies. For the nanocomposite with 2 wt% MWNTs, the regional network was destroyed and the orientation of the MWNTs during shearing exhibited a very strong shear thinning effect. The complex viscosities (|η*|) of the nanocomposites are larger than that of neat PA11 and decreased with increasing the temperature. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

Poly(glycidyl methacrylate) (PGMA) was synthesized by the RAFT method in the presence of 2-cyanoprop-2-yl dithiobenzoate (CPDB) chain transfer agent using different [GMA]/[CPDB] molar ratios. The living radical polymerization resulted in controlled molecular weights and narrow polydispersity indices (PDI) of approximate to 1.1. The polymerization of pentafluorostyrene (PFS) with PGMA as the macro-RAFT agent yielded narrow PDIs of

Well-defined organic/inorganic hybrid fluorinated star polymers were synthesized via atom transfer radical polymerization (ATRP) of 2,2,3,4,4,4-hexafluorobutyl methacrylate (HFBMA) using octa(aminophenyl)silsesquioxane (OAPS) nano-cage as initiator. For this purpose, OAPS was transformed into ATRP initiator by reacting with 2-bromoisobutyrylbromide. ATR polymerization of HFBMA was carried out in trifluorotoluene at 75 degrees C using CuCl/2,2-bipyridine or N,N,N',N",N"-pentamethyldi-ethylenetriamine as catalyst system. GPC and H-1 NMR data confirmed the synthesis of OAPS/PHFBMA hybrid star polymer. Kinetics of the ATR polymerization of HFBMA using OAPS nano-cage initiator was also investigated. The OAPS/PHFBMA hybrid stars were found to be molecularly dispersed in solution (THF); however, TEM micrographs revealed the formation of spherical particles of similar to 120-180 nm by the OAPS/PHFBMA hybrid star polymer after solvent evaporation. Thermal characterization of the nanocomposites by differential scanning calorimetry (DSC) revealed a slightly higher glass transition temperature (T-g) (when compared with the linear PRFBMA) of higher molecular weight OAPS/PHFBMA hybrid star polymers. In contrast, lower T-g than the linear PHFBMA was observed for OAPS/PHFBMA of relatively lower molecular weight (but higher than the linear PHFBMA). Thermal gravimetric analysis (TGA) showed a significant retardation (by similar to 60 degrees C) in thermal decomposition of nanocomposites when compared with the linear PHFBMA. Additionally, surface properties were evaluated by measuring the contact angles of water on polymer surfaces. (C) 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym, Chem 46: 7287-7298, 2008

Polyhedral oligomeric silsequioxane (POSS), having eight hydroxyl groups for the preparation of nanocomposites with polyimide (PI) was synthesized by the direct hydrosilylation of allyl alcohol with octasilsesquioxane (Q8M8H) with platinum divinyltetramethyl disiloxane Pt(dvs) as a catalyst. The structure of allyl alcohol terminated-POSS (POSS-OH) was confirmed by FTIR, NMR, and XRD. A high performance, low-k PI nanocomposite from pyromellitic dianhydride (PMDA)-4,4'-oxydianiline (ODA) polyamic acid cured with POSS-OH was also successfully synthesized. The incorporation of POSS-OH into PI matrix reduced dielectric constant of PI without loosing mechanical properties. Furthermore, the effects of POSS-OH on the morphology and properties of the PI/POSS-OH nanocomposites were investigated using UV–vis, FTIR, XRD, SEM, AFM, transmission electron microscope (TEM), TGA, and contact angle. The homogeneous dispersion of POSS particles was confirmed by SEM, AFM, and TEM. The nanoindentation showed that the modulus increased upon increasing the concentration of POSS-OH in PI, whereas the hardness did not increase very much with respect to loading of POSS, due to soft-interphase around POSS molecules in the resulting nanocomposites. Overall results demonstrated the nanometer-level integration of the polymer and POSS-OH. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5887–5896, 2008

Amphiphilic diblock copolymers of polystyrene (PS) and poly(N-vinylpyrrolidone) (PNVP) were prepared by a combination of ATRP and MADIX. Well-defined PS with bromine end group was synthesized by ATRP in bulk at 110 degrees C using (1-bromoethyl) benzene as an initiator. The Br- end group was then converted to xanthate as verified by H-1 NMR spectroscopy, elemental analysis, and UV-spectroscopy. PS-b-PNVP copolymers were produced by MADIX of NVP in bulk at 60 degrees C using PS-xanthate as a macro-chain transfer agent and the kinetics of polymerization were investigated. The structures of PS-b-PNVP were characterized using GPC and H-1 NMR. Amphiphilic PS-b-PNVP could form spherical micelles with PS cores and PNVP shells in aqueous solution as confirmed by H-1 NMR and laser light scattering (LLS). The values of critical micelle concentration of PS-b-PNVP and the average aggregation number of PS-b-PNVP in the micelles were measured using pyrene as a probe and static LLS, respectively. The aggregation number increases concomitantly with temperature (10-50 degrees C), but the hydrodynamic radius of the micelles remains almost constant over the same temperature range, which may indicate shell dehydration at a higher temperature. (C) 2008 Wiley Periodicals, Inc.

The interaction between PI and partially exfoliated clay nanofillers is investigated by studying the thermomechanical properties of the resulting nanocomposites by NMR, XPS, XRD, TEM, TGA, TMA, and DMA. XRD and TEM showed more exfoliated structure at

The synthesis and characterization of hydrogen-bonded star-shaped complexes consisting of stilbazolyloxy, azopyridyl, and Schiff base-substituted cyclotriphosphazenes (3a, 3b, and 3c, respectively) and monoalkyloxy, bis(dodecyloxy), and tris(dodecyloxy)benzoic acids are reported. The thermal behaviors of complexes are studied by the means of differential scanning calorimetry, polarizing optical microscopy, and X-ray diffractometry. Only 3a and 3b with monoalkyloxybenzoic acids show a homeotropic smectic A mesophase. The effect of azo and ethylene linkage of mesogenic groups in the cyclotriphosphazenes and the length of the flexible chain in monoalkyloxybenzoic acids on mesophase transition behaviors are investigated, revealing that the linkages in mesogenic groups governs the phase transition temperatures, and the length of flexible chain in proton donors plays an important role in controlling the magnitude of enthalpy and entropy of mesophase transitions in this supramolecular liquid crystal system.