Synthesis of copolymers containing a spiro orthocarbonate moiety and evaluation of the volume change during their cationic crosslinking

Spiro orthocarbonate (SOC) monomers having either an exomethylene group {3,3‐dimethyl‐9‐methylene‐1,5,7,11‐tetraoxaspiro[5.5]undecane (ExoSOC)} or an allyl group {9‐allyl‐3,3‐dimethyl‐1,5,7,11‐tetraoxaspiro[5.5]undecane (AllylSOC)} were radically copolymerized with vinyl monomers at several feed ratios to obtain the corresponding copolymers having SOC moieties in the side chain. The obtained copolymers were crosslinked via the double ring‐opening polymerization of the SOC moieties by a treatment with boron trifluoride etherate. The volume changes during the crosslinking of the copolymers were evaluated by density measurements with a gas pycnometer. As the SOC moiety composition increased, the volume shrinkage during the crosslinking was suppressed, and that finally changed into volume expansion. The volume changes during the crosslinking of the copolymers from AllylSOC were slightly larger than those of the copolymers from ExoSOC. The higher volume expansions in the crosslinking of AllylSOC‐based copolymers were ascribable to the lower steric hindrance around the SOC moieties. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 7040–7053, 2006     

Synthesis and properties of fluorene‐based polyheteroarylenes for photovoltaic devices

Novel copolymers consisting of the alternating push–pull comonomers fluorene and thieno[3,4‐b]pyrazine/quinoxaline were synthesized by a palladium‐catalyzed Suzuki cross‐coupling reaction in 60–80% yields. The structure of the deeply colored copolymers was confirmed with ¹H and ¹³C NMR. All the new materials were characterized with spectroscopic and electrochemical methods. Bulk heterojunction organic solar cells based on some of the novel polymers in combination with the well‐known fullerene acceptor [6,6]‐phenyl C₆₁–butyric acid methyl ester were fabricated, and their photovoltaic parameters were measured. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6952–6961, 2006     

White electroluminescence from a single polymer: A blue‐emitting polyfluorene incorporating orange‐emitting benzoselenadiazole segments on its main chain

We have developed efficient white‐light‐emitting polymers through the incorporation of low‐bandgap orange‐light‐emitting benzoselenadiazole ( BSeD ) moieties into the backbone of a blue‐light‐emitting bipolar polyfluorene (PF) copolymer, which contains hole‐transporting triphenylamine and electron‐transporting oxadiazole pendent groups. By carefully controlling the concentrations of the low‐energy‐emitting species in the resulting copolymers, partial energy transfer from the blue‐fluorescent PF backbone to the orange‐fluorescent segments led to a single polymer emitting white light and exhibiting two balanced blue and orange emissions simultaneously. Efficient polymer light‐emitting devices prepared using this copolymer exhibited luminance efficiencies as high as 4.1 cd/A with color coordinates (0.30, 0.36) located in the white‐light region. Moreover, the color coordinates remained almost unchanged over a range of operating potentials. A mechanistic study revealed that energy transfer from the PF backbone to the low‐bandgap segments, rather than charge trapping, was the main operating process involved in the electroluminescence process. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2938–2946, 2007     

Aggregation behavior of MPEG‐PCL diblock copolymers in aqueous solutions and morphologies of the aggregates

Poly(ethylene glycol)‐b‐polycaprolactone (MPEG‐PCL) diblock copolymers were synthesized via a ring‐opening polymerization of ε‐CL monomers with MPEG as an initiator. Their solubilities and apparent critical micelle concentrations (CMC) in aqueous solution were investigated as well as the determination of the micellar hydrodynamic diameter using dynamic light scattering (DLS). As PCL block length increased, the solubility and CMC decreased while diameters of micelles increased. The gel–sol transition behaviors were investigated using a vial tilting method. Aqueous solutions of copolymers undergo a gel to sol transition with increase in temperature when their polymer concentrations are above a critical gel concentration (CGC). The CGC of the copolymers and gel–sol transition temperature are influenced by the PCL chain length. The tapping mode AFM was performed by imaging the freeze‐dried deposits from the copolymer solutions on mica to investigate a process from free chains to micelles and to gel. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3406–3417, 2006     

Library synthesis and characterization of 3‐aminopropyl‐terminated poly(dimethylsiloxane)s and poly(ϵ‐caprolactone)‐b‐poly(dimethylsiloxane)s

Libraries of 3‐aminopropyl‐terminated poly(dimethylsiloxane) (APT–PDMS) and poly(?‐caprolactone)–poly(dimethylsiloxane)–poly(?‐caprolactone) (PCL—PDMS–PCL) triblock copolymers were synthesized. Preliminary experiments were carried out to select an appropriate catalyst and route for the poly(dimethylsiloxane) synthesis, and trial experiments were conducted to verify the successful synthesis of the intended polymer compositions. Then, a series of APT–PDMS oligomers were synthesized with an automated combinatorial high‐throughput synthesis system to cover a molecular weight range of 2500–50,000 g/mol. Trial PCL—PDMS–PCL triblock copolymers were synthesized with the automated reactor system and characterized in detail with rapid gel permeation chromatography, high‐throughput Fourier transform infrared, nuclear magnetic resonance, and differential scanning calorimetry. Finally, two library synthesis experiments were carried out in which the lengths of both the poly(dimethylsiloxane) and poly(?‐caprolactone) blocks in the PCL—PDMS–PCL triblock copolymers were varied. The results obtained from these experiments demonstrated that it was possible to synthesize libraries of well‐defined APT–PDMS oligomers and PCL—PDMS–PCL triblock copolymers with an automated high‐throughput system. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4880–4894, 2006     

Synthesis and MALDI‐TOF analysis of dendritic‐linear block copolymers of lactides: Influence of architecture on stereocomplexation

Formation of a stereocomplex from polylactide copolymers can be tuned by changing the size and the chain topology of the second block in the copolymer. In particular, the use of a dendritic instead of linear architecture is expected to destabilize the cocrystallisation of polylactide blocks. With this idea in mind, dendritic‐linear block copolymers were synthesized by ring‐opening polymerization (ROP) of lactides using benzyl alcohol dendrons of generation 1–3 as macroinitiators and stannous octoate as catalyst. Polymers with controlled and narrow molar mass distribution were obtained. The MALDI‐TOF mass spectra of these dendritic‐linear block copolymers show well‐resolved signals. Remarkably, 10% or less of odd‐membered polymers are present, indicating that ester‐exchange reactions which occur classically parallel to the polymerization process, were in these conditions, very limited. Thermal analysis of polyenantiomers of generation 1–3 and the corresponding blends were examined. The blend of a pair of enantiomeric dendritic‐linear block copolymers exhibit a higher melting temperature than each copolymer, characteristic for the formation of a stereocomplex. Melting temperatures are strongly dependent on the dendron generation. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6782–6789, 2006     

Synthesis and properties of star‐shaped polymers by the ring‐opening polymerization of cyclic carbonate initiated with a trifunctional,poly(ethylene glycol)‐based surfactant

Amphiphilic, star‐shaped copolymers were synthesized by the ring‐opening polymerization of trimethylene carbonate initiated with a trifunctional, poly(ethylene glycol)‐based surfactant (polyoxyethylene sorbitan monolaurate) in the absence of any catalysts. The metal‐ and solvent‐free polymerization proceeded at 150 °C and afforded polyoxyethylene sorbitan monolaurate‐block‐poly(trimethylene carbonate) with number‐average molecular weights of 4500–11,900 in excellent yields. The copolymers successfully dispersed in a water/ethyl acetate (10/1 v/v) mixture, and the uniform suspension could contain a hydrophobic pigment and pyrene. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6633–6639, 2006     

Thermal dissociation behavior of copolymers bearing hemiacetal ester moieties and their reactions with epoxides

Copolymers from 1‐propoxyethyl methacrylate and various vinyl monomers such as n‐butyl methacrylate and styrene were synthesized, and the thermal dissociation reaction of the copolymers containing the hemiacetal ester structure was examined. The copolymers, having the ability of thermal dissociation, could control the thermal dissociation temperature because of the bulkiness and flexibility of the vinyl comonomers, the copolymer compositions, and so on. Furthermore, the possibility of control of the initiation in thermally latent addition with epoxides in the case of copolymers was also studied. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3966–3977, 2006     

Syntheses and characterization of 16‐arm star and star diblock copolymer and AB8 9‐miktoarm star copolymer via NMRP and ROP from dendritic multifunctional macroinitiators

A dendritic macroinitiator having 16 TEMPO‐based alkoxyamines, Star‐16 , was prepared by the reaction of a dendritic macroinitiator having eight TEMPO‐based alkoxyamines, [G‐3]‐OH , with 4,4′‐bis(chlorocarbonyl)biphenyl. The nitroxide‐mediated radical polymerization (NMRP) of styrene (St) from Star‐16 gave 16‐arm star polymers with PDI of 1.19–1.47, and NMPR of 4‐vinylpyridine from the 16‐arm star polymer gave 16‐arm star diblock copolymers with PDI of 1.30–1.43. The ring‐opening polymerization of ε‐caprolactone from [G‐3]‐OH and the subsequent NMRP of St gave AB₈ 9‐miktoarm star copolymers with PDI of 1.30–1.38. The benzyl ether linkages of the 16‐arm star polymers and the AB₈ 9‐miktoarm star copolymers were cleaved by treating with Me₃SiI, and the resultant poly(St) arms were investigated by size exclusion chromatography (SEC). The SEC results showed PDIs of 1.23–1.28 and 1.18–1.22 for the star polymers and miktoarm stars copolymers, respectively, showing that they have well‐controlled poly(St) arms. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1159–1169, 2007.     

Solubilizing single‐walled carbon nanotubes with pyrene‐functionalized block copolymers

The effect of pyrene distribution within pyrene‐functionalized random and block copolymers on noncovalent polymer/single‐walled carbon nanotube (SWNT) interactions was investigated. The block copolymers served as superior solubilizing agents in comparison with the random copolymers. Also, increasing the pyrene content within a polymer, while a constant molecular weight was maintained, improved SWNT solubility and therefore had to result in stronger polymer–nanotube interactions. However, increasing the length of the pyrene‐containing block diminished nanotube solubility, likely because of a lower number of polymer chains that were capable of binding to the nanotube surface. Atomic force microscopy and transmission electron microscopy indicated that the polymer–SWNT interactions were capable of partially debundling the nanotubes into individual solvated structures. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1941–1951, 2006     

Copolymerization of N‐vinylcaprolactam and glycidyl methacrylate: Reactivity ratio and composition control

Free‐radical copolymerizations of N‐vinylcaprolactam (VCL) and glycidyl methacrylate (GMA) were investigated to synthesize temperature‐responsive reactive copolymers with minimized compositional heterogeneity. The average copolymer composition was determined by Fourier transform infrared and nuclear magnetic resonance techniques. The reactivity ratios for VCL and GMA were found to be 0.0365 ± 0.0009 and 6.44 ± 0.36 by the Fineman–Ross method and 0.039 ± 0.006 and 6.75 ± 0.29 by the Kelen–Tudos method, respectively. When prepared by batch polymerization, VCL–GMA copolymers had a highly heterogeneous composition and fractions of different solubilities in water. The use of a gradual feeding technique, which included the sequential addition of more reactive GMA monomer into the reaction, yielded copolymers with much more homogeneous composition. The produced copolymers with 0.9 and 0.11 fractional GMA contents preserved their temperature‐responsive properties and precipitated from aqueous solutions when the temperature exceeded 31 °C. The GMA units in the VCL–GMA copolymers were capable of reacting with amino end‐functionalized poly(ethylene oxide) at room temperature to produce poly(N‐vinylcaprolactam)–poly(ethylene oxide) graft copolymers. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 183–191, 2006     

Synthesis and optical and electrochemical properties of copolymers containing 9,9‐dihexylfluorene and 9‐dimethylaminopropylcarbazole chromophores

Soluble and well‐defined 9,9‐dihexylfluorene and 9‐dimethylaminopropylcarbazole based copolymers PFCN and 5PFCN have been prepared by Suzuki coupling polymerization. For comparison, alternate copolymer of 9,9‐dihexylfluorene and 9‐hexylcarbazole (PFC) was also prepared with the same method. Furthermore, alternate copolymer of 9,9‐dihexylfluorene and 9‐dimethylethylammoniumpropylcarbazole (PFCNE) was prepared from PFCN by the ethylation of its dimethylaminopropyl groups with bromoethane. These copolymers were soluble in organic solvents and showed high glass‐transition temperatures (75–160 °C). The optimized architecture of PFCN from a simulation was a spiral, which was different from the linear structure of poly(9,9‐dihexylfluorene) (PFO). Thermogravimetric analysis showed that the residual weights of 5PFCN, PFCN, PFC, and PFCNE at 800 °C were all greater then 50%, whereas PFO showed complete thermal decomposition. Both the absorption and photoluminescence emission peaks of these copolymers showed blueshifts after the introduction of the carbazole units because of reduced conjugation. Moreover, the introduction of 9‐hexylcarbazole and 9‐dimethylamionpropylcarbazole moieties into copolymers PFC and PFCN, respectively, effectively prevented the excimer formation of PFO. According to cyclic voltammetry results, PFCNE containing quaternary amino pendant groups exhibited the most stable reduction–oxidation cycles. The turn‐on electric fields of their electroluminescence devices decreased with increasing carbazole content because of the more balanced carrier injection. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3882–3895, 2006     

Synthesis and characterization of liquid‐crystalline block copolymers with cyanoterphenyl moieties by atom transfer radical polymerization

A series of new mesomorphic block copolymers composedofdifferentmacroinitiators, including poly(ethylene oxide), polystyrene, and poly(ethylene oxide)‐b‐polystyrene,and polymethacrylate with a pendent cyanoterphenyl group were synthesized through atom transfer radical polymerization. The number‐average molecular weights of the three diblock copolymers, determined by gel permeation chromatography, were 10,254, 9,772, and 15,632 g mol^?1, and their polydispersity indices were 1.17, 1.28, and 1.34. The mesomorphic and optical properties of all the block copolymers were investigated, and they possessed a smectic A phase with mesophasic ranges wider than 100 °C. Moreover, X‐ray diffraction patterns provided evidence of the smectic A phase and the corresponding interdigitated packing of all the polymers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4593–4602, 2006     

ABA triblock copolymers with a ring‐opening metathesis polymerization/macromolecular chain‐transfer agent approach

Block copolymers containing polystyrene and polycyclooctene were synthesized with a ring‐opening metathesis polymerization/chain‐transfer approach. Polystyrene, containing appropriately placed olefins, was prepared by anionic polymerization and served as a macromolecular chain‐transfer agent for the ring‐opening metathesis polymerization of cyclooctene. These unsaturated polymers were subsequently converted to the corresponding saturated triblock copolymers with a simple heterogeneous catalytic hydrogenation step. The molecular and morphological characterization of the block copolymers was consistent with the absence of significant branching in the central polycyclooctene and polyethylene blocks [high melting temperatures (114–127 °C) and levels of crystallinity (17–42%)]. A dramatic improvement in both the long‐range order and the mechanical properties of a microphase‐separated, symmetric polystyrene–polycyclooctene–polystyrene block copolymer sample was observed after fractionation. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 361–373, 2007     

Synthesis,characterization, and thermal properties of dendrimer‐star,block‐comb copolymers by ring‐opening polymerization and atom transfer radical polymerization

Novel and well‐defined dendrimer‐star, block‐comb polymers were successfully achieved by the combination of living ring‐opening polymerization and atom transfer radical polymerization on the basis of a dendrimer polyester. Star‐shaped dendrimer poly(?‐caprolactone)s were synthesized by the bulk polymerization of ?‐caprolactone with a dendrimer initiator and tin 2‐ethylhexanoate as a catalyst. The molecular weights of the dendrimer poly(?‐caprolactone)s increased linearly with an increase in the monomer. The dendrimer poly(?‐caprolactone)s were converted into macroinitiators via esterification with 2‐bromopropionyl bromide. The star‐block copolymer dendrimer poly(?‐caprolactone)‐block‐poly(2‐hydroxyethyl methacrylate) was obtained by the atom transfer radical polymerization of 2‐hydroxyethyl methacrylate. The molecular weights of these copolymers were adjusted by the variation of the monomer conversion. Then, dendrimer‐star, block‐comb copolymers were prepared with poly(L ‐lactide) blocks grafted from poly(2‐hydroxyethyl methacrylate) blocks by the ring‐opening polymerization of L ‐lactide. The unique and well‐defined structure of these copolymers presented thermal properties that were different from those of linear poly(?‐caprolactone). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6575–6586, 2006     

High‐efficiency,electrophosphorescent polymers with porphyrin–platinum complexes in the conjugated backbone: Synthesis and device performance

A series of soluble, conjugated, electrophosphorescent copolymers with (meso‐tetraphenylporphyrinato‐κ⁴N)platinum(II) (PtTPP) complexes incorporated into the polymer main chain were synthesized through the copolymerization of narrow‐band‐gap monomeric porphyrin–platinum(II) complexes and wide‐band‐gap dialkyl‐substituted fluorene monomers by a modified Suzuki coupling reaction. The study of the photoluminescence decay indicated that poly[2,7‐(9,9‐dioctylfluorene)‐co‐2,12‐((meso‐tetraphenylporphyrinato‐κ⁴N)platinum(II))] (PFO–PtTPP) was a triplet emitter. The electroluminescence emission from the fluorene segment was completely quenched for copolymers with PtTPP contents as low as 0.5 mol %. The PFO–PtTPP copolymers emitted deep red light. The device based on the porphyrin–platinum(II) copolymer PFO–5PtTPP (with 5 mol % PtTPP in the copolymer) showed the highest external quantum efficiency of 1.95% with an emission peak at 684 nm in an indium tin oxide/poly(3,4‐ethylenedioxythiophene)/polyvinylcarbazole (PVK)/70:30 (w/w) PFO–5PtTPP: 2‐(biphenyl‐4‐yl)‐5‐(4‐tert‐butylphenyl)‐1,3,4‐oxadiazole/Ba/Al device configuration. In comparison with the PFO–PtTPP copolymers synthesized via a postpolymerization metalation route, copolymerization from Pt metal complexes proved to be a more efficient synthetic route for high‐efficiency electrophosphorescent polymers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4174–4186, 2006     

Formation of honeycomb‐structured,porous films via breath figures with different polymer architectures

Honeycomb‐structured, porous films with pore sizes ranging from 200 nm to 7 μm were prepared with breath figures. The regularity of the hexagonal array and the pore size was influenced by the polymer architecture and the casting conditions. A nanoscaled suborder next to the microarray was obtained with amphiphilic block copolymers. These films were shown to be suitable as surfaces for cell growth. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2363–2375, 2006     

Synthesis and characterization of poly(arylene ether sulfone) copolymers with sulfonimide side groups for a proton‐exchange membrane

A sulfonimide‐containing comonomer derived from 4,4′‐dichlorodiphenylsulfone was synthesized and copolymerized with 4,4′‐dichlorodiphenylsulfone and 4,4′‐biphenol to prepare sulfonimide‐containing poly(arylene ether sulfone) random copolymers (BPSIs). These copolymers showed slightly higher water uptake than disulfonated poly(arylene ether sulfone) copolymer (BPSH) controls, but their proton‐conductivity values were very comparable to those of the BPSH series with similar ion contents. The proton conductivity increased with the temperature for both systems. For samples with 30 mol % ionic groups, BPSI showed less temperature dependence in proton conductivity and slightly higher methanol permeability in comparison with BPSH. The thermal characterization of the sulfonimide copolymers showed that both the acid and salt forms were stable up to 250 °C under a nitrogen atmosphere. The results suggested that the presumed enhanced stability of the sulfonimide systems did not translate into higher protonic conductivity in liquid water. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6007–6014, 2006     

Controlled radical polymerization by carboxyl‐ and hydroxyl‐terminated dithiocarbamates and xanthates

Carboxyl‐ and hydroxyl‐terminated dithiocarbamates and xanthates were practically synthesized. Carboxyl‐ and hydroxyl‐terminated polymers were made from them. These reversible addition–fragmentation chain transfer (RAFT) agents had low chain‐transfer constants that resulted in wider molecular distributions for the polymers. Nevertheless, kinetic studies showed that the polymerization behaved like a RAFT‐mediated process after a fast start. ¹H NMR and matrix‐assisted laser desorption/ionization spectra confirmed that the functional group or groups were cleanly transferred to the polymer end or ends. The copolymerization of methacrylates and acrylates could bring the former under control during radical polymerization. Block copolymers were synthesized through the condensation of the functional polymers with other types of functional polymers or through the condensation of the functional agents followed by radical polymerization. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4298–4316, 2006     

Phosphorylated copolymers containing pendant,crosslinkable spiro orthoester moieties

The synthesis of a novel spiro orthoester containing monomer, 1,4,6‐trioxaspiro[4.4]‐2‐nonylmethyl acrylate, is presented. This monomer was polymerized via a free‐radical system to yield the homopolymer and a series of copolymers with phosphorus‐containing comonomers. Diethyl vinyl phosphonate, allyldiphenylphosphine oxide, and diethyl(methacryoyoxymethyl)phosphonate were used in various feed ratios to produce copolymers with different phosphorous concentrations containing crosslinkable spiro orthoester side‐chain units. The crosslinking of the polymers was performed cationically with ytterbium triflate, and in all cases, the expansion of the polymer was observed. Moreover, the incorporation of phosphorus into the copolymers increased the limiting oxygen indices, regardless of the percentage of phosphorus used. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6728–6737, 2006