Synthesis of pyrene‐capped polystyrene for dispersion of pristine single‐walled carbon nanotubes

Pyrene‐capped polystyrene (PyPS) with various molecular weights (M?_n) was synthesized through the anionic polymerization method and characterized using UV, Fourier transform infrared and NMR spectroscopy and gel permeation chromatography. The polymers were then used for non‐covalent functionalization of pristine single‐walled carbon nanotubes (SWNTs). The functionalization efficiency was assessed by measuring the SWNT dispersibility in chloroform. In the presence of PyPS, the dispersibility can be as high as 372.5 mg L^?1, and the dispersions containing more than 1.25 mg mL^?1 of PyPS are very stable with no solid deposits observed after being centrifuged at 5000 rpm for 15 min. Once the PyPS concentration is converted to the molar concentration of the pyrene unit and the dispersibility redefined as nanotube content per molar pyrene unit, the renewed dispersibility is found to be independent of M?_n of PyPS within the detected M?_n range. For a certain PyPS polymer, however, both nanotube dispersibility and dispersion stability are strongly dependent on the PyPS concentration. These results suggest that PyPS may be used as an excellent dispersant for subsequent preparation of polystyrene/SWNT composites. Copyright © 2011 Society of Chemical Industry     

ABCBA Pentablock Copolymers Consisting of Poly(l‐lactide) (PLLA: A), Poly(d‐lactide) (PDLA: B), and Poly(butylene succinate) (PBS: C): Effects of Semicrystalline PBS Segments on the Stereo‐Crystallinity and Properties

A new stereo pentablock copolymer consisting of poly(l ‐lactide) (PLLA: A), poly‐d ‐lactide (PDLA: B), and poly(butylene succinate) (PBS: C) is synthesized by two‐step ring‐opening polymerization of d ‐ and l ‐lactides in the presence of bis‐hydroxyl‐terminated PBS prepolymer that has been prepared by the ordinary polycondensation. The pentablock copolymers (PLLA‐PDLA‐PBS‐PDLA‐PLLA) as well as the triblock copolymers (PLLA‐PBS‐PLLA) obtained as the intermediates show different properties depending on the polymer compositions. In the pentablock copolymers, the direct connection of the PLLA and PDLA blocks allows easy formation of the stereocomplex crystals, while the introduction of the semicrystalline PBS block is effective not only for changing the crystallization kinetics but also for imparting an elastomeric property.

     

Synthesis and properties of fluoroalkyl end‐capped sulfobetaine polymers

A variety of fluoroalkyl end‐capped 3‐[N‐(3‐acrylamido)propyl‐N,N‐dimethylammonio]propanesulfonate polymers [R_F–(APDAPS)_n–R_F] were prepared by the reactions of fluoroalkanoyl peroxides with the corresponding monomer under very mild conditions. Similarly, fluoroalkyl end‐capped 2‐vinylpyridinio propane sulfonate polymer was obtained by the use of fluoroalkanoyl peroxide. These fluoroalkyl end‐capped sulfobetaine polymers exhibited a good solubility in water; however, these polymers have a poor solubility in other solvents. In particular, R_F–(APDAPS)_n–R_F polymers caused gelation in methanol, although R_F–(VPPA)_n–R_F polymer showed no gelation in methanol. R_F–(APDAPS)_n–R_F polymers were found to form the self‐assembled molecular aggregates with the aggregations of the end‐capped fluoroalkyl segments and the ionic interactions between sulfobetaine segments in aqueous solutions. On the other hand, it was suggested that R_F–2‐vinylpyridinio propane sulfonate (VPPS)_n–R_F polymer is not likely to form the self‐assemblies in aqueous solutions because of the steric hindrance of pyridiniopropyl betaine units in polymer. We also studied the surfactant properties of R_F–(APDAPS)_n–R_F and R_F–(VPPS)_n–R_F polymers compared with those of other fluoroalkyl end‐capped betaine‐type polymers such as 2‐acrylamido‐2‐methylpropanesulfonic acid polymers and 2‐(3‐acrylamidopropyldimethylammonio) ethanoate polymers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1144–1153, 2004     

Fluorescence studies on the interaction between pyrene‐labelled poly(acrylic acid) and cyclodextrins

The interactions, in aqueous media, between a pyrene‐labelled polyelectrolyte poly(acrylic acid) (PAAMePy) with two different degrees of labelling and β‐ and γ‐cyclodextrins (β‐ and γ‐CD) were studied using absorption and fluorescence (steady‐state and time‐resolved) techniques. In addition to qualitative and quantitative parameters obtained from absorption and steady‐state fluorescence spectra, time‐resolved fluorescence data are presented, allowing additional important observations regarding the nature of the interactions. From the overall data it was possible to conclude that in the case of interaction with γ‐CD the efficient encapsulation of two pyrene units into the cavity of the cyclodextrin molecule leads to a decrease in the number of available free monomers and an increase in the number of preformed ground‐state dimers (GSDs) of pyrene. It was also shown that contrary to the situation in water, where only intramolecular interactions are present, the addition of γ‐CD leads to new interpolymeric interactions. The absence of significant changes is noted when the interactions of PAAMePy polymers take place with β‐CD. The excimer‐to‐monomer fluorescence intensity ratio (I_E/I_M) was found to increase with the added amount of γ‐CD but not with β‐CD. This increase is justified on the basis of the increase of the GSD contribution. The photophysical behaviour was found to be dependent on the pH of the media, but with the absence of relevant interactions between CD and PAAMePy polymer at alkaline values. Copyright © 2007 Society of Chemical Industry     

Synthesis,physical properties,and crystallization of optically active poly(L‐phenyllactic acid) and poly(L‐phenyllactic acid‐co‐L‐lactic acid)

Optically active poly(L ‐phenyllactic acid) (Ph‐PLLA), poly(L ‐lactic acid) (PLLA), and poly(L ‐phenyllactic acid‐co‐L ‐lactic acid) with weight‐average molecular weight exceeding 6 × 10³ g mol^?1 were successfully synthesized by acid catalyzed direct polycondensation of L ‐phenyllactic acid and/or L ‐lactic acid in the presence of 2.5–10 wt % of p‐toluenesulfonic acid. Their physical properties and crystallization behavior were investigated by differential scanning calorimetry, thermogravimetry, and polarimetry. The absolute value of specific optical rotation ([α]) for Ph‐PLLA (?38 deg dm^?1 g^?1 cm³) was much lower than that of [α] for PLLA (?150 deg dm^?1 g^?1 cm³), suggesting that the helical nature was reduced by incorporation of bulky phenyl group. PLLA was crystallizable during solvent evaporation, heating from room temperature, and cooling from the melt. Incorporation of a very low content of bulky phenyllactyl units even at 4 mol % suppressed the crystallization of L ‐lactyl unit sequences during heating and cooling, though the copolymers were crystallizable for L ‐phenylactyl units up to 6 mol % during solvent evaporation. The activation energy of thermal degradation (ΔE_td) for Ph‐PLLA (200 kJ mol^?1) was higher than that for PLLA (158 kJ mol^?1). The ΔE_td for the copolymers increased with an increase in L ‐phenyllactyl unit content. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis of ω‐pyrenyl‐functionalized poly(1,3‐cyclohexadiene)

ω‐Pyrenyl‐functionalized poly(1,3‐cyclohexadiene) (PCHD) was successfully synthesized by the postpolymerization reaction of poly(1,3‐cyclohexadienyl)lithium (PCHDLi) with 1‐chloromethylpyrene (ClMe‐PY). This postpolymerization reaction consisted of two competitive reactions: the addition reaction of the pyrenyl group, and a hydrogen abstraction reaction (lithiation) as a side reaction. The degree of nucleophilicity of PCHDLi was a very important factor for suppression of the side reaction, and the PCHDLi/amine system, which has high nucleophilicity, produced high ω‐pyrenyl‐functionalization for PCHD. The UV/vis and fluorescence spectra for ω‐pyrenyl‐functionalized PCHD were bathochromically shifted, relative to that of pyrene. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and characterization of poly(L‐lactide)‐poly(ethylene glycol) multiblock copolymers

Poly(L‐lactide)‐poly(ethylene glycol) multiblock copolymers with predetermined block lengths were synthesized by polycondensation of PLA diols and PEG diacids. The reaction was carried out under mild conditions, using dicyclohexylcarbodiimide as the coupling agent and dimethylaminopyridine as the catalyst. The resulting copolymers were characterized by various analytical techniques, such as GPC, viscometry, ¹H‐NMR, FTIR, DSC, X‐ray diffractometry, and contact angle measurement. The results indicated that these copolymers presented outstanding properties pertinent to biomedical use, including better miscibility between the two components, low crystallinity, and hydrophilicity. Moreover, the properties of the copolymers can be modulated by adjusting the block length of the two components or the reaction conditions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1729–1736, 2002; DOI 10.1002/app.10580     

Characterization of biaxial strain of poly(l‐lactide) tubes

Poly(l ‐lactide) in its l ‐form has promising mechanical properties. Being a semicrystalline polymer, it can be subjected to strain‐induced crystallization at temperatures above T_g and can thereby become oriented. Following a simultaneous (SIM) biaxial strain process or a sequential (SEQ) biaxial strain process, the mechanical properties of biaxially strained tubes can be further improved. This study investigated these properties in relation to their morphology and crystal orientation. Both processes yield the same mechanical strength and modulus, yet exhibit different crystal orientation. Through further wide angle X‐ray scattering analysis it was found that the SEQ biaxial strain yields larger interplanar spacing and distorted crystals and looser packing of chains. However, this does not influence the mechanical properties negatively. A loss of orientation in SEQ biaxially strained samples at high degrees of strain was detected, but was not seen for SIM biaxial strain and did not correlate with mechanical performance in either case. However, post‐annealing reduced the orientation to the same level in both cases, and the modulus and strength decreased for both SIM and SEQ biaxial strain. It is therefore concluded that mechanical properties after biaxial strain are related to strain‐induced amorphous orientation and the packing of crystals, rather than strain‐induced crystallinity. © 2015 Society of Chemical Industry     

Crystallization and morphology of cholesterol end‐capped poly(ethylene glycol)

Crystallization and morphology of polyethylene glycol with molecular weight M_n = 2000 (PEG2000) capped with cholesterol at one end (CS‐PEG2000) and at both ends (CS‐PEG2000‐CS) were investigated. It is found that the bulky cholesteryl end group can retard crystallization rate and decrease crystallinity of PEG, especially for CS‐PEG2000‐CS. Isothermal crystallization kinetics shows that the Avrami exponent of CS‐PEG2000 decreases as crystallization temperature (T_c). The Avrami exponent of CS‐PEG2000‐CS increases slightly with T_c, but it is lower than that of CS‐PEG2000. Compared to the perfect spherulite morphology of PEG2000, CS‐PEG2000 exhibits irregular and leaf‐like spherulite morphology, while only needle‐like crystals are observed in CS‐PEG2000‐CS. The linear growth rate of CS‐PEG2000 shows a stronger dependence on T_c than PEG2000. The cholesterol end group alters not only the free energy of the folding surface, but also the temperature range of crystallization regime. The small angle X‐ray scattering (SAXS) results show that lamellar structures are formed in all these three samples. By comparing the long periods obtained from SAXS with the theoretically calculated values, we find that the PEG chains are extended in PEG2000 and CS‐PEG2000, but they are once‐folded in CS‐PEG2000‐CS. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2464–2471, 2007     

Synthesis and characterization of an amphiphilic hyperbranched poly(amine‐ester)‐co‐D,L‐lactide (HPAE‐co‐PLA) copolymers and their nanoparticles for protein drug delivery

A series of hyperbranched poly(amine‐ester)‐co‐D ,L ‐lactide (HPAE‐co‐PLA) copolymer were synthesized by ring‐opening polymerization of D ,L ‐lactide with Sn(Oct)₂ as catalyst to a fourth generation branched poly(amine‐ester) (HPAE‐OHs4). The chemical structures of copolymers were determined by FTIR, ¹H‐NMR, ¹³C‐NMR, and TGA. Double emulsion (DE) and nanoprecipitation (NP) method were used to fabricate the nanoparticles of these copolymers encapsulating bovine serum albumin (BSA) as a model. DSC thermo‐grams indicated that the nanoparticles with BSA kept stable below 40°C. Different factors which influence on particular size and encapsulation efficiency (EE) were investigated. Their EE to BSA could reach 97.8% at an available condition. In vitro release behavior of NPs showed a continuous release after a burst release. The stability maintenance of BSA in the nanoparticle release in vitro was also measured via circular dichroism and fluorescence spectrometry. The results showed that the copolymer nanoparticles have a promising potential in protein delivery system. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effects of plasma treatment on biocompatibility of poly[(L‐lactide)‐co‐(ϵ‐caprolactone)] and poly[(L‐lactide)‐co‐glycolide] electrospun nanofibrous membranes

Poly[(l ‐lactide)‐co ‐(? ‐caprolactone)] (PLCL) and poly[(l ‐lactide)‐co ‐glycolide] (PLGA) copolymers are widely used in neural guide tissue regeneration. In this research, the surface modification of their hydrophilicity was achieved using plasma treatment. Attachment and proliferation of olfactory ensheathing cells on treated electrospun membranes increased by 26 and 32%, respectively, compared to the untreated PLCL and PLGA counterparts. Cells cultivated on both the PLCL and PLGA membranes showed high viability (>95%) and healthy morphologies with no evidence of cytotoxic effects. Cells grown on treated electrospun fibres displayed significant increases in mitochondrial activity and reductions in membrane leakage when compared to untreated samples. The results suggested that plasma treatment of the surface of the polymers enhanced both cell viability and growth without incurring any cytotoxic effects. © 2017 Society of Chemical Industry     

Synthesis,characterization, and fluorescence properties of lanthanide complexes with poly(styrene‐co‐methacrylic acid)

A series of new complexes of poly(styrene‐co‐methacrylic acid) with Ln(III) (Ln = La, Eu, Tb) were synthesized and well characterized by means of elemental analysis, FTIR, differential scanning calorimetric (DSC) analysis, TG‐DTA analysis, X‐ray diffraction (XRD), and fluorescence determination. The elemental analysis and FTIR studies showed that a large part of carboxylic groups on the side chain of the copolymer are coordinated with Ln(III) ions. The TG‐DTA and DSC analysis results indicated that the complexes have good thermal stability. XRD experiments showed that copolymers and the complexes are amorphous. Among these complexes, Eu(III) complexes and Tb(III) complexes exhibit characteristic fluorescence with comparatively high brightness and good monochromaticity. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Part 7. Effects of poly(L‐lactide‐co‐ϵ‐caprolactone) on morphology,structure, crystallization,and physical properties of blends of poly(L‐lactide) and poly(ϵ‐caprolactone)

Blended films of poly(L ‐lactide) [ie poly(L ‐lactic acid)] (PLLA) and poly(?‐caprolactone) (PCL) without or mixed with 10 wt% poly(L ‐lactide‐co‐?‐caprolactone) (PLLA‐CL) were prepared by solution‐casting. The effects of PLLA‐CL on the morphology, phase structure, crystallization, and mechanical properties of films have been investigated using polarization optical microscopy, scanning electron microscopy, differential scanning calorimetry and tensile testing. Addition of PLLA‐CL decreased number densities of spherulites in PLLA and PCL films, and improved the observability of spherulites and the smoothness of cross‐section of the PLLA/PCL blend film. The melting temperatures (T_m) of PLLA and PCL in the films remained unchanged upon addition of PLLA‐CL, while the crystallinities of PLLA and PCL increased at PLLA contents [X_PLLA = weight of PLLA/(weight of PLLA and PCL)] of 0.4–0.7 and at most of the X_PLLA values, respectively. The addition of PLLA‐CL improved the tensile strength and the Young modulus of the films at X_PLLA of 0.5–0.8 and of 0–0.1 and 0.5–0.8, respectively, and the elongation at break of the films at all the X_PLLA values. These findings strongly suggest that PLLA‐CL was miscible with PLLA and PCL, and that the dissolved PLLA‐CL in PLLA‐rich and PCL‐rich phases increased the compatibility between these two phases. © 2003 Society of Chemical Industry     

Application of low loading of collagen in electrospun poly[(l‐lactide)‐co‐(ε‐caprolactone)] nanofibrous scaffolds to promote cellular biocompatibility

Electrospinning of various polymers has been used to produce nanofibrous scaffolds that mimic the extracellular matrix and support cell attachment for the potential repair and engineering of nerve tissue. In the study reported here, an electrospun copolymer of l ‐lactide and ε‐caprolactone (67:33 mol%) resulted in a nanofibrous scaffold with average fibre diameter and pore size of 476 ± 88 and 253 ± 17 nm, respectively. Blending with low loadings of collagen (<2.5% w/w) significantly reduced the average diameter and pore size. The uniformity of fibre diameter distributions was supported with increasing collagen loadings. The nanofibrous scaffolds significantly promoted the attachment and proliferation of olfactory ensheathing cells compared to cells exhibiting asynchronous growth. Furthermore, analysis of cell health through mitochondrial activity, membrane leakage, cell cycle progression and apoptotic indices showed that the nanofibrous membranes promoted cell vigour, reducing necrosis. The study suggests that the use of more cost‐effective, low loadings of collagen supports morphological changes in electrospun poly[(l ‐lactide)‐co‐(ε‐caprolactone)] nanofibrous scaffolds, which also support attachment and proliferation of olfactory ensheathing cells while promoting cell health. The results here support further investigation of the electrospinning of these polymer blends as conduits for nerve repair. © 2013 Society of Chemical Industry     

Poly(lactide‐co‐glycolide) solution behavior in supercritical CO2, CHF3, and CHClF2

Cloud point and solution density data between 20 and 100°C and pressures to 3000 bar are presented for poly(lactide) (PLA) and poly(lactide‐co‐glycolide) (PLGA_x, where the molar concentration of glycolide in the backbone x ranges from 0 to 50 mol %) in supercritical CO₂, CHClF₂, and CHF₃. PLA dissolves in CO₂ at pressures near 1400 bar, in CHF₃ at pressures of 500 to 750 bar, and in CHClF₂ at pressures of 20–100 bar. As glycolide (GA) is added to the backbone of PLGA, the cloud point pressure increases by 50 bar/(mol GA) in CO₂, 25 bar/(mol GA) in CHF₃, and by only 2.5 bar/(mol GA) in CHClF₂. PLGA₅₀ does not dissolve in CO₂ to pressures of 3000 bar whereas it is readily soluble in CHClF₂ at pressures as low as 100 bar at 50°C. In comparison, the increases in cloud point pressure with increasing weight average molecular weight (M_w) are only approximately 2.3 bar/(1000 M_w) for PLGA copolymers in CO₂. The solution densities with all three SCF solvents range from 1.1 to 1.5 g/cm³ and they vary only by a small amount over the 80°C range used to obtain cloud point data. More than likely, the ability of the acidic hydrogen in CHF₃ and CHClF₂ to complex with the ester linkage in PLGA makes these better solvents than CO₂ especially since any change in favorable energetic interactions is magnified due to the liquid‐like densities exhibited by these SCF solvents. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1155–1161, 2001     

Miscibility,morphology and thermal properties of poly(para‐dioxanone)/poly(D,L‐lactide) blends

BACKGROUND: Poly(para‐dioxanone) (PPDO) is a biodegradable polyester with excellent biodegradability, bioabsorbability, biocompatibility and mechanical flexibility. However, its high cost and relatively fast degradation rate have hindered the development of commercial applications. Blending with other polymers is a simple and convenient way of modifying the properties of aliphatic polyesters. Poly(D ,L ‐lactide) (PDLLA) is another polyester that has been extensively studied for biomedical applications due to its biocompatibility and suitable degradation rate. However, to our knowledge, blends of PPDO/PDLLA have not been reported in the literature. RESULTS: A series of biodegradable polymers were blended by solution co‐precipitation of PPDO and PDLLA in various blend ratios. The miscibility, morphology and thermal properties of the materials were investigated. DSC curves for all blends revealed two discrete glass transition temperatures which matched the values for pure PPDO and PDLLA. SEM images of fracture surfaces displayed evidence of phase separation consistent with the DSC results. The contact angles increased with the addition of PDLLA. CONCLUSION: PPDO/PDLLA blends exhibit two distinct glass transition temperatures that remain nearly constant and correspond to the glass transition temperatures of the homopolymers for all blend compositions, indicating that blends of PPDO and PDLLA are immiscible. Images of the surface obtained using SEM were also suggestive of a two‐phase material. The crystallinity of the PPDO phase in the blends was affected by the PDLLA content. The mechanical properties of the blends changed dramatically with composition. Adding PDLLA makes the blends less hydrophilic than PPDO. Copyright © 2008 Society of Chemical Industry     

Fully biobased biodegradable poly(l‐lactide)‐b‐poly(ethylene brassylate)‐b‐poly(l‐lactide) triblock copolymers: synthesis and investigation of relationship between crystallization morphology and thermal properties

Well‐defined poly(l ‐lactide‐b‐ethylene brassylate‐b‐l ‐lactide) (PLLA‐b‐PEB‐b‐PLLA) triblock copolymer was synthesized by using double hydroxyl‐terminated PEBs with different molecular weights. Gel permeation chromatography and NMR characterization were employed to confirm the structure and composition of the triblock copolymers. DSC, wide‐angle X‐ray diffraction, TGA and polarized optical microscopy were also employed to demonstrate the relationship between the composition and properties. According to the DSC curves, the cold crystallization peak vanished gradually with decrease of the PLLA block, illustrating that the relatively smaller content of PLLA may lead to the formation of a deficient PLLA type crystal, leading to a decrease of melting enthalpy and melting temperature. Multi‐step thermal decompositions were determined by TGA, and the PEB unit exhibited much better thermal stability than the PLLA unit. Polarized optical microscopy images of all the triblock samples showed that spherulites which develop radially and with an extinction pattern in the form of a Maltese cross exhibit no ring bond. The growth rate of the spherulites of all triblock samples was investigated. The crystallization capacity of PLLA improved with incorporation of PLLA, which accords with the DSC and wide‐angle X‐ray diffraction results. © 2019 Society of Chemical Industry     

The influence of the preparation conditions and filler content on thermal properties of poly‐l‐lactide and hydroxyapatite/poly‐l‐lactide nanocomposite

Poly‐l ‐lactide (PLLA) and hydroxyapatite/poly‐l ‐lactide (HAp/PLLA) are two widely used biomaterials for three‐dimensional scaffolds, drug release matrices and implantable medical devices for reparation of bone tissue; diversity in the initial preparation and filler content has a significant influence on different properties such as morphology and crystallinity, thus playing a considerable role in most of these applications. For this reason, PLLA and HAp/PLLA samples with a large difference in crystallinity (from below 20% to over 70%) and filler content (up to 86 wt% of HAp nanoparticles with an average diameter of 80 nm) were prepared and consequent dissimilarities in morphology, crystallinity and thermal properties were investigated by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), wide angle X‐ray diffraction (WAXD) measurements and Fourier transform infrared (FTIR) spectroscopy. Special attention was devoted to analyzing data obtained from thermal measurements. A three‐phase model was employed in order to describe the heat capacity step decline in the nanocomposite; the evolution in different polymer fractions, the crystalline fraction and the mobile and rigid amorphous fractions, with filler content was determined. © 2017 Society of Chemical Industry     

Synthesis and characterization of greenish‐blue emitting vinyl copolymer containing pyrene and triarylamine moieties

Two fluorescent monomers N‐phenyl‐N‐(4‐vinylphenyl)pyren‐1‐amine (vinyl‐PyPA) and 1‐vinyl pyrene (VPy) were synthesized in good yields. A series of soluble conductive vinyl copolymers P(PyPA‐co‐VPy) containing vinyl‐PyPA and VPy moieties in different composition ratios were prepared by free radical solution polymerization. These copolymers showed high T_g (190?201 °C) and good thermal stability. The photoluminescence emission maxima of the copolymers were all in the range 474.5?478.5 nm, which was similar to the poly(N‐phenyl‐N‐(4‐vinylphenyl)pyren‐1‐amine) (P(PyPA)) (475 nm) but blue shifted compared with poly(1‐vinyl pyrene) (PVPy) (490.5 nm). The lifetime of the copolymers increased from 10.2 to 29.7 ns with an increase in pyrene content. The copolymers had higher quantum yields (0.51) than those of the homopolymers of P(PyPA) (0.48) and PVPy (0.13). The highest occupied molecular orbital of the copolymers remained relatively unchanged from P(PyPA), while the lowest unoccupied molecular orbital varied from ?2.41 eV to ?2.51 eV with an increase in pyrene ratio in the copolymers. The energy bandgaps of the copolymers (from 2.70 eV to 2.81 eV) were smaller than those of P(PyPA) (2.82 eV) and PVPy (3.47 eV). Two polymer light‐emitting diode (PLED) series were attempted including indium tin oxide (ITO) (fluorocarbon (CFx) treated)/P(PyPA‐co‐VPy)/LiF/Al and ITO(CFx treated)/P(PyPA‐co‐VPy)/1,3,5‐Tri(1‐phenyl‐1H‐benzo[d]imidazol‐2‐yl)phenyl (TPBi)/LiF/Al. The results suggested that the PyPA moiety is hole conducting and the PLEDs can achieve high luminance from 650 to 1150 cd m^?2 (at 100 mA cm^?2) only when an electron injecting layer TPBi is employed. © 2013 Society of Chemical Industry     

Synthesis and applications of silicone oil–soluble fluoroalkyl end‐capped cooligomers

Fluoroalkyl end‐capped cooligomers containing polydimethylsiloxane and polyoxyethylene segments were prepared under very mild conditions by the cooligomerizations of fluoroalkanoyl peroxides with methacrylate monomers containing the corresponding segments and comonomers such as dimethylacrylamide and acryloylmorpholine. These obtained fluorinated cooligomers exhibited amphipathic characteristics and became soluble in water and common organic solvents. In particular interest, fluoroalkyl end‐capped cooligomers containing polyoxyethylene units were soluble not only in poly(methylphenylsiloxane) (silicone oil) but also in water, including common organic solvents except for hexane. Additionally, these fluorinated cooligomers were able to reduce the surface tension of water and m‐xylene quite effectively, to around 15 and 20 mN/m levels, respectively. In these fluorinated cooligomers, fluoroalkyl end‐capped acryloylmorpholine cooligomers containing polyoxyethylene segments were applicable as a novel emulsifying agent against water and silicone oil. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1467–1476, 2005