Poly(3‐hexylthiophene)‐block‐poly(2‐ethyl‐2‐oxazoline) amphiphilic rod–coil diblock copolymers have been synthesized by a combination of Grignard metathesis (GRIM) and ring‐opening cationic polymerization. Diblock copolymers containing 5, 15, and 30 mol‐% poly(2‐ethyl‐2‐oxazoline) have been synthesized and characterized. The synthesized rod–coil block copolymers display nanofibrillar morphology where the density of the nanofibrills is dependent on the concentration of the poly(2‐ethyl‐2‐oxazoline) coil segment. The conductivity of the diblock copolymers was lowered from 200 to 35 S · cm?1 with an increase in the content of the insulating poly(2‐ethyl‐2‐oxazoline) block. By contrast, the field‐effect mobility decreased by 2–3 orders of magnitude upon the incorporation of the poly(2‐ethyl‐2‐oxazoline) insulating segment.
A copolymer of 2,3,5,6‐tetrafluoro‐1,4‐phenylenevinylene and 2,5‐dioctyloxy‐1,4‐phenylenevinylene [co(TFPV‐DOPV)], containing more than 60% of tetrafluorophenylenevinylene monomeric units, was synthesized by the Stille cross‐coupling reaction. Its linear and nonlinear optical properties were investigated. Linear absorption and photoluminescence measurements performed on thin films and solution indicate interchain migration upon excitation. The Z‐scan technique was used to evaluate the third‐order nonlinear susceptibility at λ = 1064 nm. A very high refractive nonlinearity (n2 = (?10 ± 2) × 10?12 cm2 · W?1) was measured with a value one order of magnitude larger than that of the corresponding dialkoxy‐substituted homopolymer.
Summary: The pH response of the micelles of polystyrene‐block‐poly(acrylic acid) (PS200‐b‐PAA78) in water is studied using a combination of techniques: static light scattering (SLS), dynamic light scattering (DLS), and transmission electron microscopy (TEM). The structure of the micelles in dilute aqueous solution is dependent on pH. At pH values <2.5, the micelles precipitate. At pH values from 2.5 to 3.5, the micelles associate to form micellar clusters. At pH values ranging from 3.5 to 8.0, the micelles are dynamically frozen. At pH > 8.1, some PS200‐b‐PAA78 unimers gradually escape from the micelles and subsequently re‐associate to form smaller micelles.
The pH‐responsive behavior of the PS200‐b‐PAA78 micelles in solution. 相似文献
Poly(4,4‐bis[(3,5‐diethoxybenzoyloxy)methyl]‐1,6‐heptadiyne) is synthesized via cyclopolymerization using modified Grubbs‐ and Schrock‐type initiators. Doping with either I2 or NO+ BF4? yields a conductive polymer with conductivity up to 1.4 × 10?2 S cm?1. The undoped amorphous conjugated polymer is spun into monofilament and multifilament fibers by a wet‐spinning process. Fibers are collected on bobbins with a draw down ratio of 12 resulting in fiber diameters under 60 μm, characterized by scanning electron microscopy. X‐ray diffraction data confirms that the amorphous structure of the polymer is preserved; no additional orientation of the polymer chains occurs during fiber spinning.
Summary: Two series of novel α,ω‐perfluoroalkyl terminated esters of poly(ethylene oxide) (PEO) (RF‐PEO) having the general structure CmF2m+1? COO? (CH2? CH2? O)n? OC? CmF2m+1, with m = 1,2,3,4 or 5 have been synthesized. The influences of the PEO molar mass, the length of the perfluoroalkyl group (RF) and temperature on the cleavage of the ester bridge in aqueous solution and the effect of the hydrolysis process on the size of aggregates formed in water were studied. According to 1H and 19F NMR measurements the degree of functionalization obtained (up to 96 mol‐%) increases with the decrease in the length of the RF group. All of the derivatives showed ester cleavage in water in short time scales. The rates of hydrolysis of the ester bridge in aqueous solution were determined from pH‐measurements. It was verified that the rate law for hydrolysis corresponds to a pseudo‐first order type. The hydrolysis kinetic constant k increased with a decrease in the length of the RF group ranging from 0.2 × 10?3 s?1 for the longest RF group (C5F11? ) up to 1.2 × 10?2 s?1 for the shortest RF group (CF3? ). The value of k depended almost exclusively on the length of the perfluoroalkyl chain and was independent of the length of the PEO backbone (1 000 or 2 000 g · mol?1), as long as no additional phenomenon such as phase separation was present. It was also found that the change in the value of k with temperature followed a non‐Arrhenius pattern and there was an evident relationship between the non‐linearity in the ln k vs. 1/T relation with increasing temperatures and the occurrence of a macroscopic phase separation of LCST type. Dynamic light scattering measurements showed the coexistence of unimers with associated species with apparent hydrodynamic radii (Rh) of approximately 20–45 nm for all samples in aqueous solutions. These species might correspond to aggregates of a few micelles. For some samples also larger aggregates were found with Rh in the 100–500 nm range, which might be attributed to clusters of micelles.
1,2,4‐triazole‐functional PGMA polymers have been synthesized and their anhydrous proton‐conducting properties were investigated after doping with phosphoric acid and triflic acid. PGMA was prepared by solution polymerization and then modified with 1H‐1,2,4‐triazole (Tri) and 3‐amino‐1,2,4‐triazole (ATri). FT‐IR, 13C NMR and elemental analysis verify the high immobilization of the triazoles in the polymer chain. Phosphoric‐acid‐doped polymers showed lower Tg and higher proton conductivities. PGMA‐Tri 4 H3PO4 showed a maximum water‐free proton conductivity of approximately 10?2 S · cm?1 while that of PGMA‐ATri 2 H3PO4 was 10?3 S · cm?1. The structure and dynamics of the polymers were explored by 1H MAS and 13C CP‐MAS solid‐state NMR.
Poly(3‐hexylthiophene)‐block‐poly(tetrahydrofuran) was synthesized by cationic ring‐opening polymerization of tetrahydrofuran (THF) using a poly(3‐hexylthiophene) macroinitiator. Poly(3‐hexylthiophene) macroinitiator used for the ring‐opening polymerization of THF was synthesized by reacting the hydroxypropyl end‐group with trifluoromethanesulfonic anhydride in the presence of 2,6‐di‐tert‐butylpyridine. 1H NMR spectroscopy and SEC data confirmed the formation of the di‐block copolymers. Field‐effect mobility of poly(3‐hexylthiophene)‐block‐poly(tetrahydrofuran) was measured in a thin‐film transistor configuration and was found to be 0.009 cm2 · V?1 · s?1.
Summary: Hole transporting poly(N‐vinylcarbazole) copolymers with phenylazomethine dendron units acting as metal ligation sites were synthesized. These polymers possess both hole‐transport and metal‐collecting units with simple σ‐bond linkages. Complexation in the phenylazomethine dendron unit within these copolymers by SnCl2 has been successfully observed by the change in the UV‐vis spectra. The complexation changes the HOMO/LUMO energy gap that results in a spectral red‐shift. Using copolymers as a hole‐transport layer, only complexation with metal ions leads to an enhanced maximum luminescence. Such a complexation results in a high electroluminescence efficiency because the p‐type‐doped structure acts as the hole‐transport layer.
Copolymerization for the preparation of DPAGn(x)‐Cbz(y). 相似文献
Poly(ethylene oxide) of various molecular weights (Mn = 3 000, 5 200, 10 000, 16 500 g · mol?1) has been modified with terpyridine end groups as building blocks for water‐soluble metallo‐supramolecular polymers. Metallo‐supramolecular A–A homopolymers have been prepared and characterized by complexing the terpyridine units of one selected poly(ethylene oxide) (Mn = 3 000 g · mol?1) with the following transition metal ions in their 2+ oxidation state: Fe, Ru, Co, Ni, Cu, Zn, and Cd. In addition, the stability of the supramolecular connection with respect to pH variations has been investigated.
Schematic representation of the product of poly(ethylene oxide) modification with terpyridine end groups and the metal complexation. 相似文献
The synthesis and the characterization of main‐chain liquid‐crystalline poly(ether esters), derived from hydroxybibenzoic acid and (R,S)‐ and (R)‐2‐methylpropane‐1,3‐diol, are reported. These polymers show an interesting thermal behavior. They develop mesophases with a slow rate of formation, allowing the easy quenching of the melt into: a) the glassy amorphous state, b) the glassy liquid‐crystalline state, or c) a mixture of both, depending on the thermal treatment. The extent of the transformation and the symmetry of the different phases have been determined by means of calorimetric and X‐ray diffraction methods. Dielectric spectroscopy results provide additional evidence for the detection of distinct glass transitions. The results show that the racemic polymer forms a low‐ordered SmCalt mesophase, while a more ordered phase is obtained in the case of the enantiomerically pure polymer. The comparison of the properties of the different states evidences the special behavior and properties of the glass transition (Tg) in these polymers. Emphasis is paid to the location of the Tg of the liquid‐crystalline state in comparison to the Tg of the amorphous state. It is found that the glass transition of the SmCalt glass in R,S‐PBO3 (the poly(ether ester) derived from hydroxybibenzoic acid and (R,S)‐2‐methylpropane‐1,3‐diol) appears at lower temperatures than the glass transition of the amorphous state. However, in R‐PBO3 (the poly(ether ester) derived from hydroxybibenzoic acid and (R)‐2‐methylpropane‐1,3‐diol), where the more ordered phase is present, the glass transition follows the classical tendency of semicrystalline polymers.
A novel graft copolymer is synthesized from commercially available poly(vinyl alcohol) using ring‐opening polymerization. For the polymerization reaction of novel brush‐like poly(vinyl alcohol)‐graft‐poly(?‐caprolactone‐co‐(3‐/7‐(prop‐2‐ynyl)oxepan‐2‐one) 5 Sn(Oct)2 is used as a catalyst. The formation of the graft copolymer is confirmed by 1H NMR, 13C NMR, and Fourier transform infrared (FTIR) spectroscopy. Furthermore, the modification of the novel synthesized graft copolymer via a “click” reaction to implement adamantane groups is described. The success of the “click” reaction is proven by 1H NMR spectroscopy and visualized by decomplexation of cyclodextrin with included phenolphthalein.
Summary: The crystallization behavior of crystalline‐crystalline diblock copolymer containing poly(ethylene oxide) (PEO) and poly(ε‐caprolactone) (PCL), in which the weight fraction of PCL is 0.815, has been studied via differential scanning calorimeter (DSC), wide‐angle X‐ray diffraction (WAXD), and polarized optical microscopy (POM). DSC and WAXD indicated that both PEO and PCL blocks crystallize in the block copolymer. POM revealed a ring‐banded spherulite morphology for the PEO‐b‐PCL diblock copolymer.
DSC heating curve for the PEO‐b‐PCL block copolymer. 相似文献
CROP has been used to synthesize well‐defined POXZ with a monofunctional (iodomethane) or a bifunctional (1,3‐diiodopropane) initiator. POXZ has been functionalized with an azido group at one (α‐azido‐POXZ, = 3.58 × 103 g · mol?1) or both ends (α,ω‐azido‐POXZ, = 6.21 × 103 g · mol?1) of the macromolecular chain. The Huisgen 1,3‐dipolar cycloaddition has been investigated between azido‐POXZ and a terminal alkyne on a small or larger molecule (PEG). In each case, the click reaction has been successful and quantitative. In this way, different telechelic polymers (polymers bearing different functions such as acrylate, epoxide, or carboxylic acid) and block copolymers of POXZ and PEG have been prepared. The polymers have been characterized by means of FTIR, 1H NMR, and SEC.
Summary: Blends of high molecular weight poly(R‐3‐hydroxybutyrate) (PHB) ( = 352 000 g · mol?1), comprising of either low molecular weight poly(R‐3‐hydroxybutyrate) (D‐PHB) ( = 3 900 g · mol?1) or poly[(R‐3‐hydroxybutyrate)‐co‐(R‐3‐hydroxyvalerate)] (PHBV) ( = 238 000 g · mol?1) with 12 mol‐% hydroxyvalerate (HV) content as a second constituent, were investigated along with the thermal properties and morphologies. After isothermal crystallization, a lowering of the melting temperature of PHB can be observed with increasing content of the second component in the blends. This behavior points towards miscibility of the constituents both in the liquid and the solid state. Crystallization kinetics was studied under isothermal and non‐isothermal conditions. The overall kinetics of isothermal crystallization was analyzed in terms of the Avrami equation. Only one crystallization peak is observed in all cases for the PHB/D‐PHB and PHB/PHBV blends under the conditions studied. This demonstrates co‐crystallization of the constituents. The addition of D‐PHB or PHBV to PHB reduces the rate of crystallization of the blends compared to that of neat PHB. The corresponding activation energies of crystallization also decrease with an increasing concentration of the second constituent. Non‐isothermal crystallization, carried out with different cooling rates held constant, is discussed in terms of a quasi‐isothermal approach. The corresponding rate constants as functions of reciprocal undercooling show Arrhenius‐like behavior in a certain range of temperatures. At sufficiently high undercooling, the rate constants of crystallization for the isothermal process exceed those reflecting non‐isothermal conditions, whereas in the limit of low undercoolings, the rate constants become similar. Ring‐banded morphologies are observed when PHB is in excess. When the respective second component is the major component, fibrous textures of the spherulites develop.
Two hydrophobically modified PNIPAM semitelechelics PxF9 were prepared by “clicking” PNIPAM containing an azide endgroup (PxN3) with nonadecafluoro‐1‐decyl hex‐5‐ynoate (F9). Micelles of PxF9 in water with a core of F9‐segments and a PNIPAM corona were detected by dynamic light scattering and by 1H and 19F NMR spectroscopy below the LCST. Just below the LCST, the PNIPAM chains start to collapse onto the F9 core followed by aggregation of several collapsed micelles to large particles in the range of ≈110 nm. The F9 segments shifted the LCST to lower temperatures when comparing PxN3 with PxF9. The existence of micelles in PxF9 solutions also improved the reversibility of the LCST behavior as measured by DSC.
3,5‐Bis(bromomethyl)pyridine hydrobromide and 3,5‐bis(bromobutyl)pyridine hydrobromide were synthesized from commercially available 3,5‐lutidine. The poly(N‐alkylation) of these monomers readily yielded new hyperbranched polyelectrolytes. The progress of reaction was followed by 1H NMR. A second‐order kinetic scheme fits the experimental data. Rate constants and activation parameters were determined, showing the higher reactivity of 3,5‐bis(bromomethyl)pyridine hydrobromide. This was explained by the electron‐attractive effect of pyridinium groups on the ? CH2Br end groups. The structures of the hyperbranched poly[3,5‐bis(alkylene)pyridinium]s were investigated by 1H and 13C NMR spectroscopy and a preliminary study of their properties is reported.
The crystalline structure and crystallization behavior of PLLA crystals in a 1:1 w/w mixture of low‐MW PLLA with high‐MW PDLA were analyzed using WAXD, DSC, and SAXS. Under cold crystallization, homopolymeric PLLA, appearing as a meta crystal, was discovered in the PDLA/LMW‐PLLA blend. The meta‐ and α′ crystal forms of PLLA were found to form on crystallization at a Tcc of 85–95 °C and the α crystal PLLA formed at 100 ≤ Tcc < 120 °C. The meta‐crystal PLLA may be incorporated in the stereocomplexed PDLA/LMW‐PLLA lamellar region. During heating, the meta‐crystal PLLA first partially melted and then repacked directly into the α crystal PLLA without going through the less‐stable α′ form.
Summary: Optically pure (+) and isotactic poly[{methyl(1‐naphthyl)silylene}(o‐phenylene)methylene] terminated with methylphenylchlorosilyl was obtained by the Pt‐catalyzed ring‐opening polymerization of optically pure 1‐methyl‐1‐(1‐naphthyl)‐2,3‐benzosilacyclobut‐2‐ene in the presence of methylphenylchlorosilane as a chain transfer agent. The polymer formed was transformed into a block copolymer by reacting the terminal chlorosilyl group with a commercial poly(ethylene glycol) monomethyl ether. The formation of micelles by the block copolymer in THF‐water mixtures was investigated by fluorescence and UV. More detailed information about the aggregation of the polymer in the micelles was obtained by circular dichroism spectroscopy. It was found that dense aggregates were formed at a concentration higher than the critical micelle concentration. This concentration was higher for lower molecular weight polymer, at higher temperatures, and in more hydrophobic solvent systems. The highly aggregated structure was altered by changing the solvent system.
The concept of micellar catalysis was transferred to the hydroaminomethylation of 1‐octene with N,N‐dimethylamine. In the first series of experiments a rhodium(I ) complex with amphiphilic triphenylphosphane functionalized poly(2‐oxazoline)s as macroligand was applied as catalyst. Results obtained under standard hydroformylation conditions (T = 100 °C, p = 50 bar) were not satisfying with regard to activities and selectivities of the hydroaminomethylation reaction. Rising the temperature to 150 °C increased the yield of amine to 22% with a corresponding n/iso selectivity of 7.5 and a TOF number of 461 h?1. Best results were obtained by applying a dual Rh/Ir catalyst within the polymeric micelles leading at lower temperature of 130 °C to an amine yield of 24% with a corresponding n/iso selectivity of 11 and TOF numbers of about 600 h?1.
