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In this article, ABA triblock copolymer (tri-BCP) thermoplastic elastomers with poly(ethylene oxide) (PEO) middle block and polyzwitterionic poly(4-vinylpyridine) propane-1-sulfonate (PVPS) outer blocks were synthesized. The PVPS-b-PEO-b-PVPS tri-BCPs were doped with lithium bis-(trifluoromethane-sulfonyl) imide (LiTFSI) and used as solid polyelectrolytes (SPEs). The thermal properties and microphase separation behavior of the tri-BCP/LiTFSI hybrids were studied. Small-angle X-ray scattering (SAXS) results revealed that all tri-BCPs formed asymmetric lamellar structures in the range of PVPS volume fractions from 12.9% to 26.1%. The microphase separation strength was enhanced with increasing the PVPS fraction (fPVPS) but was weakened as the doping ratio increased, which affected the thermal properties of the hybrids, such as melting temperature and glass transition temperature, to some extent. As compared with the PEO/LiTFSI hybrids, the PVPS-b-PEO-b-PVPS/LiTFSI hybrids could achieve both higher modulus and higher ionic conductivity, which were attributed to the physical crosslinking and the assistance in dissociation of Li+ ions by the PVPS blocks, respectively. On the basis of excellent electrical and mechanical performances, the PVPS-b-PEO-b-PVPS/LiTFSI hybrids can potentially be used as solid electrolytes in lithium-ion batteries. [ABSTRACT FROM AUTHOR]

In this work, the advanced all solid-state block copolymer electrolytes (SBCPEs) for lithium-ion batteries with double conductive phases, poly(ethylene oxide)-b-poly(trimethyl-N-((2-(dimethylamino)ethyl methacrylate)-7-propyl)-ammonium bis(trifluoromethanesulfonyl) imide) (PEO-b-PDM-dTFSI)/LiTFSI, were fabricated, in which the charged PDM-dTFSI block contained double quaternary ammonium cations and the PEO block was doped with LiTFSI. The disordered (DIS) and ordered lamellae (LAM) phase structures were achieved by adjusting the composition of the block copolymer and the doping ratio r. In addition, the presence of the hard PDM-dTFSI block and the formation of the LAM phase structure resulted in a good mechanical strength of the solid PEO-b-PDM-dTFSI/LiTFSI electrolyte, and it could maintain a high level of 104 Pa at 100 °C, which was around 10,000 times stronger than that of the PEO/LiTFSI electrolyte. Based on the good mechanical and electrochemical properties, the PEO-b-PDM-dTFSI/LiTFSI SBCPE exhibited excellent long-term galvanostatic cycle performance, indicating the strong ability to suppress lithium dendrites. [ABSTRACT FROM AUTHOR]

The strong adhesion of thermally conductive silicone encapsulants on highly integrated electronic devices can avoid external damages and lead to an improved long-term reliability, which is critical for their commercial application. However, due to their low surface energy and chemical reactivity, the self-adhesive ability of silicone encapsulants to substrates need to be explored further. Here, we developed epoxy and alkoxy groups-bifunctionalized tetramethylcyclotetrasiloxane (D4H-MSEP) and boron-modified polydimethylsiloxane (PDMS-B), which were synthesized and utilized as synergistic adhesion promoters to provide two-component addition-cured liquid silicone rubber (LSR) with a good self-adhesion ability for applications in electronic packaging at moderate temperatures. The chemical structures of D4H-MSEP and PDMS-B were characterized by Fourier transform infrared spectroscopy. The mass percentage of PDMS-B to D4H-MSEP, the adhesion promoters content and the curing temperature on the adhesion strength of LSR towards substrates were systematically investigated. In detail, the LSR with 2.0 wt% D4H-MSEP and 0.6 wt% PDMS-B exhibited a lap-shear strength of 1.12 MPa towards Al plates when curing at 80 °C, and the cohesive failure was also observed. The LSR presented a thermal conductivity of 1.59 W m−1 K−1 and good fluidity, which provided a sufficient heat dissipation ability and fluidity for potting applications with 85.7 wt% loading of spherical α-Al2O3. Importantly, 85 °C and 85% relative humidity durability testing demonstrated LSR with a good encapsulation capacity in long-term processes. This strategy endows LSR with a good self-adhesive ability at moderate temperatures, making it a promising material requiring long-term reliability in the encapsulation of temperature-sensitive electronic devices. [ABSTRACT FROM AUTHOR]

Block copolymer single crystals (BCPSCs) have attracted widespread attentions due to their unique two‐dimensional (2D) structure, good controllability, and great potential applications in recent years. In this paper, the morphology, surface structure of BCPSCs and the related influencing factors are reviewed. We also summarize the studies of 2D crystalline assemblies of block copolymers (BCPs) driven by crystallization and intermolecular π–π interaction. Moreover, the functionalization and properties of BCPSCs and 2D crystalline assemblies of BCPs are introduced. Finally, we put forward some unsolved problems in this field. [ABSTRACT FROM AUTHOR]

Poly(ethylene oxide)‐b‐poly(4‐vinylpyridine) (PEO‐b‐P4VP) block copolymers (BCPs) exhibiting lower disorder‐to‐order transition (LDOT) phase behavior are doped with different salts (LiCl, CuCl2, and FeCl3), in which both blocks can competitively associate with the metal ions. It is found that the entropy‐driven LDOT phase behavior of PEO‐b‐P4VP can be bi‐directionally adjusted by enthalpic interactions, depending on the complexation selectivity of metal ions toward two blocks and doping ratio (r). At low rs, Li+ ions preferentially interact with PEO block, leading to a decreased disorder‐to‐order transition temperature (TDOT). Cu2+ ions selectively complex with the P4VP block, and the TDOT first increases with increasing r, followed by a decrease. By contrast, Fe3+ ions interact strongly with both blocks, resulting in increase of TDOT. At high rs, the complexation selectivity becomes weaker, leading to reduced immiscibility and increased TDOT, as compared with the hybrids with low rs. The effects of metal cation and r on the LDOT phase behavior are qualitatively explained by the change of the Flory–Huggins parameter. [ABSTRACT FROM AUTHOR]

Adult neurogenesis plays a vital role in maintaining cognitive functions in mammals and human beings. Mobilization of hippocampal neurogenesis has been regarded as a promising therapeutic approach to restore injured neurons in neurodegenerative diseases including Alzheimer's disease (AD). Icarisid II (ICS II), an active ingredient derived from Epimedii Folium, has been reported to exhibit multiple neuroprotective effects. In the present study, we investigated the effects of ICS II on the proliferation and differentiation of neural stem cells (NSCs) and amyloid precusor protein (APP)‐overexpressing NSCs (APP‐NSCs) in vitro. Our results demonstrated that ICS II dose‐dependently suppressed apoptosis and elevated viability of APP‐NSCs. ICS II (1 μM) potently promoted proliferation and neuronal differentiation of NSCs and APP‐NSCs. ICS II (1 μM) significantly upregulated Wnt‐3a expression, increased the phosphorylation of glycogen synthase kinase‐3β and enhanced the nuclear transfer of β‐catenin. Moreover, ICS II also promoted astrocytes to secrete Wnt‐3a, which positively modulates Wnt/β‐catenin signaling pathway. These findings demonstrate that ICS II promotes NSCs proliferation and neuronal differentiation partly by activating the Wnt/β‐catenin signaling pathway. [ABSTRACT FROM AUTHOR]

The most daunting challenge of solid polymer electrolytes (SPEs) is the development of materials with simultaneously high ionic conductivity and mechanical strength. Herein, SPEs of lithium bis‐(trifluoromethanesulfonyl)imide (LiTFSI)‐doped poly(propylene monothiocarbonate)‐b‐poly(ethylene oxide) (PPMTC‐b‐PEO) block copolymers (BCPs) with both blocks associating with Li+ ions are prepared. It is found that the PPMTC‐b‐PEO/LiTFSI electrolytes with double conductive phases exhibit much higher ionic conductivity (2 × 10−4 S cm−1 at r.t.) than the BCP electrolytes with a single conductive phase. Concurrently, the storage moduli of PPMTCn‐b‐PEO44/LiTFSI electrolytes are ≈1–4 orders of magnitude higher than that of the neat PEO/LiTFSI electrolytes. Therefore, simultaneous improvement of ionic conductivity and mechanical properties is achieved by construction of a microphase‐separated and disordered structure with double conductive phases. [ABSTRACT FROM AUTHOR]

The crystalline memory effect is frequently observed in polymer crystallization, but the melt structure remains unresolved. In this work, the preserved spherulites in the melt of poly(L -lactide)-based block copolymers are observed by polarized optical microscopy (POM) unexpectedly. These spherulites are not erased instantly on reaching the melting temperatures, but it takes tens of minutes at a designed melting temperature to completely erase the spherulites. These preserved spherulites in the melt, where some crystalline traces are lost but the Maltese cross appearance is still obvious, are possibly attributed to the long range of molecular orientation enhanced by microphase separation between two blocks. Moreover, these preserved spherulites have a significant effect on the subsequent crystallization, i.e. a faster radius growth rate and denser nucleation. This study highlights that a thermodynamically unstable structure can be fully preserved in a supercooled melt for a long time, which has never been reported elsewhere. [ABSTRACT FROM AUTHOR]

C28H78Si10, monoclinic, Pn (no. 7), a = 21.413(4) Å, b = 9.8568(17) Å, c = 22.074(4) Å, β = 93.426(4)°, V = 4650.6(14) Å3, Z = 4, Rgt(F) = 0.0613, wRref(F2) = 0.1750, T = 296(2) K. [ABSTRACT FROM AUTHOR]

Four polymers containing five-membered rings in the main chain, with or without conjugation structure along the backbone and with or without conjugated pendent groups, were designed and synthesized by metathesis cyclopolymerization of functionalized α,ω-diynes, and cyclopolymerization of functionalized α,ω-dienes catalyzed by the α-diimine palladium-based catalyst, respectively. High to moderate monomer conversions were achieved. Chain structure, molecular weight, and molecular weight distribution (MWD) of the cyclopolymerization products were characterized by 1H-, 13C-NMR, FTIR, and GPC. The polymers showed regular main chain structures, moderately high molecular weight, and narrow MWD. Thermal properties and chain stacking behaviors of the polymers were investigated by differential scanning calorimetry (DSC) and X-ray diffraction (XRD) as well as atomic force microscopy (AFM). The polymer with conjugation system in both the backbone and the pendent groups exhibited UV-Vis absorption at a much longer wavelength than those with the conjugation only in the backbone or only in the side groups. The polymers with conjugated backbone need more space for chain stacking, and the conjugated backbone causes enhanced size of polymer particles assembled from solution. The results showed that primary microstructures of the polymer exerted significant influences on the physical properties. [ABSTRACT FROM AUTHOR]

ABSTRACT Poly( l-lactide)/polyacrylonitrile (PLLA/PAN) core-sheath composite fibers were fabricated by coaxial electrospinning. The crystallization behavior of PLLA within the coaxial electrospun fibers was studied by differential scanning calorimetry (DSC). The PLLA/PAN coaxial electrospun fiber with a PLLA diameter of ∼32 nm (C1) exhibits a crystallization temperature ( Tc) of 22.5 °C higher but a cold-crystallization temperature ( Tcc) of 10 °C lower than bulk PLLA. The crystallinity of C1 fiber is also higher than bulk PLLA. In both isothermal melt- and cold-crystallization, PLLA in C1 fiber crystallizes faster than the bulk PLLA, as revealed by the smaller half crystallization times ( t1/2). The enhanced crystallizability of PLLA in the C1 fiber may be attributed to the increased nuclei number and crystal growth rate induced by the PAN surface, i.e., surface-induction effect. However, PLLA also suffers a nano-confinement effect exerted by PAN sheath in the coaxial electrospun fiber, which can suppress PLLA crystallization. When the diameter of PLLA is too small (< 32 nm), the nano-confinement effect may prevail over the surface-induction effect, leading to a slower crystallization rate and smaller crystallinity. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45980. [ABSTRACT FROM AUTHOR]

ABSTRACT A precisely sequenced ethylene-propylene (EP) fully alternating copolymer was synthesized via trans-1,4-polymerization of isoprene catalyzed by Ziegler-Natta catalyst followed by hydrogenation. This EP copolymer was used as model polymer for studying structure-property relationship. An ethylene-propylene random copolymer (ethylene-propylene rubber [EPR]) with similar ethylene content was also prepared for comparison, and the effect of comonomer sequence distribution on properties was investigated. The copolymer chain structures were monitored by 1H and 13C NMR and Fourier translation infrared. Differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical analysis, and tensile tests were employed to determine the thermal and mechanical properties. The fully alternating copolymer EP gives a more precise glass transition comparing than EPR. Further understanding on thermal properties and aggregation behavior of ethylene-propylene copolymers is made possible by this comparative study. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45816. [ABSTRACT FROM AUTHOR]

The nanoscale structure and macroscopic morphology of π-conjugated polymers are very important for their electronic application. While ordered single crystals of small molecules have been obtained via solution deposition, macroscopically aligned films of π-conjugated polymers deposited directly from solution have always required surface modification or complex pre-deposition processing of the solution. Here, ordered nanowires were obtained via shear-enhanced crystallization of π-conjugated polymers at the air–liquid–solid interface using simple deposition of the polymer solution onto an inclined substrate. The formation of macroscopically aligned nanowire arrays was found to be due to the synergy between intrinsic (π-conjugated backbone) and external (crystallization conditions) effects. The oriented nanowires showed remarkable improvement in the charge carrier mobility compared to spin-coated films as characterized in organic field-effect transistors (OFETs). Considering the simplicity and large-scale applicability, shear-enhanced crystallization of π-conjugated polymers provides a promising strategy to achieve high-performance polymer semiconductor films for electronics applications. [ABSTRACT FROM AUTHOR]

The fluorescent properties of a linear poly(hydroxyurethane) (P1) from carbon dioxide, siloxane (Si–O–Si)-containing bisepoxide and diamine are described. P1 showed strong photoluminescence with a quantum yield of up to 23.6%, high photostability, and broad absorption and emission spectra either in bulk or solution. The flexibility and hydrophobicity of the Si–O–Si linkage in P1 were utilized to drive the intense aggregation of hydroxyurethane chromophores which combined with the hydrogen bonding interactions lead to strong photoluminescence. P1 was used as a single phosphor film for fabricating a low voltage, cool white light-emitting diode device with competitive performances. [ABSTRACT FROM AUTHOR]

The hybrid micelles of polystyrene- b-poly(( N-isopropyl acrylamide)- co-(4-vinylbenzyl chloride)) block copolymer (PS- b-P(NIPAM- co-VBC)) with Prussian blue (PB) in the corona were prepared by reaction of pentacyano(4-(dimethylamino)-pyridine)ferrate (Fe-DMAP)-attached PS- b-P(NIPAM- co-VBC) with FeCl. The formation of the PB framework inside the micelles was verified by UV-Vis, FTIR and TGA. The morphology of the hybrid micelles was studied by TEM and compared with that of the neat and Fe-DMAP-attached PS- b-P(NIPAM- co-VBC). It is found that attachment of Fe-DMAP may change the short rod-like micelles of the neat PS- b-P(NIPAM- co-VBC) into spherical ones and lead to a smaller micelle size. The morphology of the hybrid micelles may be altered or remain unchanged after formation of the PB framework, depending on the chain structure of PS- b-P(NIPAM- co-VBC) and starting concentration. The thermoresponsive behavior of different micelles was studied using DLS. It is observed that attachment of Fe-DMAP can improve the hydrophilicity of the P(NIPAM- co-VBC) block, leading to weaker hysteresis of the micelle size during the heating and cooling cycle. However, the crosslinked PB framework in the micellar corona may result in a more evident hysteresis phenomenon and blur the two-stepwise change of the micellar size with temperature. [ABSTRACT FROM AUTHOR]

ABSTRACT The self-nucleation behavior of olefinic blocky copolymer (OBC) / organically modified montmorillonite (OMMT) nanocomposites with a novel collapsed clay structure (c-OMMT) was studied and compared with that of the nanocomposites with an intercalated clay structure (OBC/i-OMMT). Their behaviors appear different in three temperature domains, Domain I (D I) in which the polymer is completely melted and only the heterogeneous nuclei are present, Domain II (D II) in which only self-nucleation occurs and Domain III (D III) where both self-nucleation and annealing take place. As the OMMT loading increases, the boundary temperature of D I and D II ( TI→II) shifts to lower temperature and D II becomes narrower. For the OBC/c-OMMT nanocomposites, the TI→II or TI→III (the boundary temperature of D I and D III) can be lower than the end melting temperature ( [ABSTRACT FROM AUTHOR]

ABSTRACT In this work, we reported calcium tetrahydrophthalate as a high efficient β-nucleating agent (β-NA) for impact-resistant polypropylene copolymer (IPC). The relative fraction of the β-crystal can reach as high as 93.5% when only 0.03% β-NA is added. The non-isothermal and isothermal crystallization behaviors, morphology, lamellar structure and mechanical properties of IPCs with various β-NA contents were studied. During non-isothermal crystallization, the cooling rate has an important influence on the relative fraction of the β-crystal, which decreases remarkably as the cooling rate increases. The β-NA also greatly accelerates crystallization rate of IPC, resulting from both more crystal nuclei and larger Avrami exponent. The small angle X-ray scattering characterization shows that more amorphous components are included into the inter-lamellae after addition of β-NA. Dynamical mechanical analysis (DMA) reveals that the storage modulus at low temperature and the loss factor above 0 °C from the PP component can be enhanced upon addition of β-NA and reach a maximum at the β-NA content of 0.05 wt %. Impact test shows that the impact strength of the IPC at 0°C can be improved as much as 40% when the content of calcium tetrahydrophthalate is 0.10 wt %. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40753. [ABSTRACT FROM AUTHOR]

Different inorganic salts, including NaSCN, NaCl, MgCl and NaSO, were added into the aqueous solution containing poly(ɛ-caprolactone)- b-poly(ethylene oxide) (PCL- b-PEO) semicrystalline micelles. The effects of inorganic salt on the micellar size and morphology were investigated with TEM and DLS. It is found that addition of NaSCN leads to increase of the micellar size, but the micelles remain to be spherical. By contrast, the other three inorganic salts can induce sphere-to-cylinder or sphere-to-lamella transformations of the PCL- b-PEO semicrystalline micelles. The alteration rate of the micellar size with the time after addition of the inorganic salts decreases in the following order: NaSO > NaCl ≈ MgCl > NaSCN. These results were interpreted in terms of the 'salting-out' ability of the cations and anions. The anions SO and Cl have a stronger 'salting-out' ability, driving the morphological transformations of the micelles and leading to a rapid change in micellar size. By contrast, SCN has a weaker salting-out' ability. The cations Na and Mg may associate with the PEO blocks, leading to a 'salting-out' effect as well. However, the 'salting-out' ability of cations is weaker than that of SO and Cl anions, and the 'salting-out' abilities of Na and Mg are similar. [ABSTRACT FROM AUTHOR]

A polydimethylsiloxane armed with epoxy, alkoxy and acrylate groups was synthesized from silanol terminated-PDMS and epoxy and acrylate groups functionalized silane coupling agents, and utilized as the adhesion promoter (AP) to prepare addition-cured liquid silicone rubber that exhibited self-adhesion ability (SA-LSR) with biocompatible thermoplastic polyurethanes (TPU) sheets. The structural characteristics of AP were characterized by Fourier transform infrared (FTIR) spectroscopy, which demonstrated the strong adhesion to polyester-based TPU sheets due to a sufficient amount of acrylate groups, epoxy groups and silanol groups obtained by the hydrolysis of alkoxy groups. In detail, the peel-off strength of SA-LSR and TPU joints reached up to 7.63 N mm−1 after the optimization of adhesion promoter including type and content, and curing condition including time and temperature. The cohesive failure was achieved during the sample breakage process. Moreover, the SA-LSR showed a good storage stability under proper storage conditions. This design strategy provided the feasibility to combine the advantages of addition-cured liquid silicone rubber and plastics with low melting points, promoting the potential application range of those silicone-based materials. [ABSTRACT FROM AUTHOR]

The isothermal crystallization kinetics of poly(ε-caprolactone) (PCL) grafted on multi-walled carbon nanotubes (MWNTs-g-PCL) with high grafting degrees were studied and compared with those of neat PCL and a PCL/MWNTs blend. The Avrami exponent n altered from 3.0 for the neat PCL to nearly 2.0 for the grafting polymers. The grafting polymers exhibit a significantly faster crystallization rate but lower crystallinity than the neat PCL and PCL/MWNTs blend. In the grafting polymers, MWNTs exert both stronger nucleation and confinement effects on the crystallization of PCL than those for the PCL/MWNTs blend. The grafting density affects crystallization of PCL more severely than the molecular weight of the grafting PCL. The crystallization activation energy of the grafting polymers is smaller than that of the PCL/MWNTs blend but larger than that of the neat PCL. The grafted PCL chains are over-crowded and highly stretched, and the PCL crystals lie on the surface of MWNTs with the b-axis basically perpendicular to the surface. [ABSTRACT FROM AUTHOR]

The chain microstructure, crystallization, and morphology of three olefinic blocky copolymers (OBCs) are compared. The weight percentage of the hard block and the octene content in it are calculated from the 13C NMR spectra with a two-site first-order Markovian model. The lengths of the hard blocks are compared from the melting and crystallization behaviors. The remarkable difference between the crystallinity measured by DSC, and wide-angle X-ray diffraction (WAXD) indicates the presence of partially ordered phases. Small angle X-ray scattering (SAXS) shows that the partially ordered phases in OBC-A are mainly located at the interface between the crystalline and amorphous phases, but exist as separated microdomains in OBC-B. As the hard block becomes shorter, there are also more, separated partially ordered phases in OBC-C. Spherulites are observed in all OBCs by POM and the size of the spherulites decreases in the order: OBC-A > OBC-B > OBC-C. TEM shows that spherulites are poorly developed in a thin film of OBC-B. [ABSTRACT FROM AUTHOR]

The microstructure and morphology of an olefinic blocky copolymer (OBC) and an ethylene-hexene copolymer prepared by conventional Ziegler-Natta catalysis (ZNEH) are compared. It is found that these two samples have similar melting temperatures, but the overall comonomer content in OBC is slightly higher. The crystallization temperature and crystallinity of OBC are markedly lower than those of ZNEH. A successive self-nucleation annealing experiment reveals that OBC has a more uniform distribution of crystal thickness, indicating a more homogeneous composition distribution in its hard blocks. Small-angle X-ray scattering (SAXS) results show that the long period of OBC hardly changes with temperature in the low-temperature range, whereas that of ZNEH increases gradually with temperature due to melting of the less perfect crystals. The average lamellar thickness of crystals is larger for OBC than for ZNEH, but the thickness of the thickest crystals is comparable in the two. The SAXS profiles were analyzed using a one-dimensional correlation function. The result reveals that the partially ordered interphases in OBC are mainly located at the interface of the crystalline and amorphous phases. In contrast, the interface of the crystalline and amorphous phases in ZNEH is quite sharp and it is inferred that the partially ordered interphases are distributed in the bulk as separated domains. Scattered tiny crystals are formed in ZNEH, but OBC exhibits a macroscopic morphology of large spherulites. It is also observed that more amorphous phases are rejected outside of the lamellar stacks and spherulites in OBC. © 2012 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

In the present work, the effect of phase separation on overall isothermal crystallization kinetics of two polypropylene/ethylene-propylene random copolymer (PP/EPR) in-reactor alloys was investigated. It is found that at lower crystallization temperatures ( T c), the overall crystallization rate decreases with increasing phase separation temperature ( T s). This is attributed to the lower linear spherulitic growth rate incurred by the lower PP content in the PP-rich phase at higher T ss. In contrast, at higher T cs, quenching from a higher T s to T c promotes nucleation as a result of more dramatic concentration fluctuation, leading to a faster overall crystallization rate. The overall crystallization rate of the PP/EPR in-reactor alloy prepared by multi-stage sequential polymerization process (MSSP) is retarded by increasing phase separation time ( t s). However, prolonging phase separation time has little effect on the crystallization rate of the sample prepared by two-stage polymerization process (TSP). This result can be attributed to the different phase separation rates of these two samples. The SAXS result confirms that at higher T c, phase separation in the melt before crystallization can retard crystallization, when compared with the directly quenched samples. It is also found that the phase-separated PP/EPR in-reactor alloys exhibit a larger long period because of more amorphous phases included between the lamellar crystals. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]

In this work, a new type of block polymers, polystyrene- b-poly[( N-isopropyl acrylamide)- co-(vinyl benzyl chloride)] (PS- b-P(NIPAM- co-VBC)), was prepared via reversible addition fragmentation transfer polymerization, then pentacyano(4-(dimethylamino pyridine))ferrate (Fe-DMAP) was attached to VBC units through a quaternization process. The Fe(II)-coordinated PS- b-P[NIPAM- co-(VBC-Fe-DMAP)] block copolymers were characterized by H-NMR, FT-IR and TGA. The self-assembly behavior of the block copolymers was also investigated and the micelle morphology was characterized by TEM. It was found that the PS- b-P(NIPAM- co-VBC) block polymer and Fe-coordinated block copolymer could both form spherical micelles in DMF/MeOH mixed solvent. [ABSTRACT FROM AUTHOR]

Films of polypropylene/organically modified montmorillonite (PP/OMMT) nanocomposites were drawn at two different temperatures with various draw ratios. The effect of OMMT on the orientations of the crystalline and amorphous phases was studied using polarized infrared spectroscopy. It is found that OMMT layers always retard the orientation of the crystalline phase. The higher the OMMT loading, the stronger the retardance effect. In contrast, the effect of OMMT layers on the orientation of the amorphous phase depends on draw temperature and OMMT loading. A favorable effect on the orientation of the amorphous phase is observed at low OMMT loading and high draw temperature, but the retardance prevails at high OMMT loading and low draw temperature. The favorable effect on orientation at high draw temperature is attributed to the stabilization effect of OMMT layers on the conformation of amorphous PP chains. Such an effect was further verified by comparing the crystallization behavior and the morphologies of drawn PP and PP/OMMT films crystallized from 180°C. Memory effect is observed for crystallization of drawn PP/OMMT film, but it is not obvious for the drawn film of neat PP. Spherulites are formed for orientated neat PP films cooled from 180°C, but cylindrites are still formed after the drawn PP/OMMT films undergo melting at 180°C and recrystallization. The stabilization effect disappears at higher temperature (230°C). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 [ABSTRACT FROM AUTHOR]

In this work, the effect of phase separation on the spherulitic growth rate of a polypropylene/ethylene-propylene random (PP/EPR) copolymer in-reactor alloy was investigated. The PP/EPR in-reactor alloy was either directly quenched from homogeneous melt to crystallization temperature or held at various temperatures for phase separation prior to crystallization. It is found that at lower crystallization temperatures previous phase separation in the melt retards the crystallization rate. The higher the phase separation rate, the smaller the spherulitic growth rate. This can be attributed to faster crystallization rate than the rate of secondary phase separation. The composition of the PP-rich phase and corresponding depression of the equilibrium melting temperature of PP vary with phase separation temperature. On the other hand, at higher crystallization temperature, previous phase separation in the melt has little effect on the spherulitic growth rate because secondary phase separation can take place prior to crystallization. The transition temperature from regime II to regime III also shifts to lower temperature as the phase separation temperature increases. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 [ABSTRACT FROM AUTHOR]

The article discusses a study of the effect of annealing treatment on the solid-phase morphology of nascent spherical polypropylene (N-PP) granules. Aldrich of China has supplied the tert-butyl perbenzoate (TBPB) which served as an initiator. Results show that side reactions often accompany grafting reactions caused by free radicals. Also noted is the capability of annealing to significantly increase the crystallinity of PP granules.

The article presents a study on the characterization and fractionation of an ethylene-propylene copolymer that was produced with a MgCl2/SiO2/TiCl4/diester-type Ziegler-Natta catalyst. The researchers used diphenyldimethoxysilane as external donor in the copolymerization. They found that the EP copolymer synthesized by a heterogeneous Ziegler-Natta catalyst system shows intramolecular and intermolecular heterogeneity.

Nanocarbons with diverse structures have great potential applications in biomedicine, energy conversion, and catalysis owing to their unique photoelectric properties. This work describes bottom‐up synthesis of hyperbranched fractal nanocarbons (HFNs), using trimethylolpropane tri(cyclic carbonate) ether and ethylenediamine as the precursors. HFNs are formed by self‐assembly of in situ generated carbonized polymer dots (CPDs), driven by their low surface ζ‐potentials. Of significance, both CPDs and HFNs possess graphitized carbon core and functionalized shell with core edge layer, thus emit bright solid‐state luminescence with an absolute quantum yield of 11.7% at room temperature and strong phosphorescence at 77 K. The carbonyl cluster of these nanocarbons is mainly responsible for the strong photoluminescence emission. The application of HFNs is demonstrated for energy conversion, using them as single phosphor for fabricating multicolor light‐emitting diodes. This work outlines a fundamental principle to prepare HFNs with bright photoluminescence in solid state. [ABSTRACT FROM AUTHOR]

One‐dimensional cylindrical micelles of block copolymers (BCPs) with a crystalline core have many advantages and potential applications. Their properties and performance are tightly related to their length. In this review, the growth kinetics and length control of cylindrical crystalline micelles of BCPs are commented. The pathways for formation of crystalline micelles are first introduced, and then the methods for preparing seed micelles (such as sonication and self‐seeding) as well as regulation of the number and crystallinity of the seed micelles are presented. The kinetics for two growth modes starting from the seed micelles, that is, epitaxial growth of unimers onto the seed micelles and end‐to‐end coupling among different micelles, are derived and various factors affecting the growth kinetics and structure of the obtained micelles, including external conditions and BCP structure, are discussed. [ABSTRACT FROM AUTHOR]