Journal of Polymer Science Part A: Polymer Chemistry

Well-defined calixarene-centered amphiphilic A₂B₂ miktoarm star copolymers [C4S(PCL)₂-(PEG)₂] were successfully synthesized by the combination of CROP and “click” chemistry. ¹H NMR, FT-IR, and SEC analyses confirmed the designed structure. Multimorphological aggregates with calix[4]arene cavities on the hydrophilic/hydrophobic interface could be obtained from the self-assembly of these miktoarm star copolymers.

The copolymer microspheres of styrene and maleic anhydride were synthesized by stabilizer-free dispersion polymerization, and the polymerization process was explored in detail. The results showed that the homopolymerization of styrene formed in initial polymerization period served as stabilizer, and reaction solvent of closer solubility parameter would benefit the stabilizer-free dispersion polymerization.

A series of highly organosoluble polyamides with high modulus having propeller-shaped triarylamine were synthesized using aromatic diacid chlorides by low-temperature solution polycondensation. These polymers revealed electrochromic characteristics both in the visible range and near-infrared (NIR) region, with a color change from pale yellowish at its neutral state to green and blue at its oxidized state at applied potentials ranging from 0.00 to 1.35 V.

We synthesized a series of Mesogen-jacketed liquid crystalline polymers (MJLCPs) with both electron-transport oxadiazole and hole-transport thiophene in the side chain. Electroluminescence study with the device configuration of ITO/PEDOT/PVK/polymer/TPBI/Ca/Ag showed maximum brightness and current efficiency of 541 cd/m² and 0.10 cd/A, which proved that the introduction of directly connected electron- and hole-transport units could greatly improve the EL property of side-chain conjugated polymers.

Mesogen jacketed liquid crystalline poly(1-alkyne) and poly(1-phenyl-1-alkyne) containing lateral pendants of terphenyl mesogen with hexyloxy tail and carboxy termethylene spacer are designed and synthesized. The polymers show enantiotropic SmA phases in the heating and cooling scans. The “jacket effect” from the mesogens around main chain endows the polymers with excellent thermal stability and high photoluminescence, and energy could transfer from the terphenyl to backbone to favor the high light emitting. In comparison with poly(1-alkyne), poly(1-phenyl-1-alkyne) shows better photoluminescence in solution and film.

A pH-responsive polyphosphonobetaine (PPB) containing a three carbon spacer between the charges has been synthesized for the first time using Butler's cyclopolymerization process. The unquenched valency of nitrogens in the zwitterionic units has permitted us to study the anionic polyeletrolyte (APP) - to - polyzwitterion transitions by viscometry and potentiometry. Contrary to known polycarbo- and sulfo-betaines, the PPB demonstrated contrasting solution behaviors in the presence of added salts. The basicity constants of the pH-triggerable amine and phonate functionalities have been determined.

We have synthesized two alternating copolymers of 2,6-bis(p-dihexylaminostyryl)-anthracene-9,10-diyl and N-octylcarbazole with large two-photon sections. The as-synthesized polymers show high glass transition temperatures and emit strong one- and two-photon excitation fluorescence. The solution two-photon absorption (TPA) properties of P1 and P2 in chloroform are measured by the two-photon-induced fluorescence method using femtosecond laser pulses (120 fs). The maximal δ of P1 and P2 all appear at ∼800 nm and are 1010 GM and 940 GM per repeating unit, respectively.

We investigated the relationship between chemical structures and refractive indices using the series of POSS derivatives. The polymer composites containing eight kinds of octa-substituted aliphatic and aromatic POSS were prepared, and the respective parameters in the Lorentz–Lorenz equation were determined from the measurements of refractive indices of the matrices. We found that POSS can intrinsically have superior ability to reduce the refractive indices. Finally, we can present the guidelines for designing effective POSS fillers to lower the refractive index.

Radical polymerization of N-tert-butoxycarbonylacrylamide (NBocAAm) was investigated in toluene at low temperatures in the presence of the fluorinated alcohols, 2,2,2-trifluoroethanol (1), 1,1,1,3,3,3-hexafluoro-2-propanol (2) and nonafluoro-tert-butanol (3). It was found that atactic, heterotactic and syndiotactic polymers were obtained by adding 1, 2, and 3, respectively. NMR analysis of the mixtures of NBocAAm and the fluorinated alcohols suggested that hydrogen bonding-assisted complexes with different structures should be formed depending on the structure of the added fluorinated alcohols. Mechanisms for the induced stereospecificity are proposed based on the structures of the hydrogen bonding-assisted complexes.

Two novel copoly(p-phenylene) ;s (P1 and P2) containing bipolar groups (12.8 and 6.8 mol %, respectively) were synthesized to enhance electrol uminescence of PPV derivatives (d6-PPV). The bipolar groups not only enhance thermal stability but also promote electron affinity and hole affinity of the copoly(p-phenylene)s. Blending the bipolar copoly(p-phenylene)s with d6-PPV effectively improve the emission efficiency of their electroluminescent devices. The maximum luminance and maximum luminance efficiency of PPV device were enhanced from 310 cd/m² and 0.03 cd/A to 1450 cd/m² and 0.20 cd/A (d6-PPV/P1 = 96/4).

Monobrominated polystyrene (PStBr) chains were activated and coupled in atom transfer radical coupling (ATRC) systems with varying equivalents of environmentally benign reducing agents. This combination of activators generated by electron transfer and ATRC lead to an overall reduction in metal content by up to 90% compared with traditional ATRC reactions while maintaining high yields of dimerization.

Hydrosilylation reaction of A₂ monomer containing bis SiH moieties and B_n (n = 2, 3, and 4) monomers containing di-, tri-, and tetra-vinyl groups in the presence of Karstedt's catalyst afforded corresponding linear and hyperbranched polycarbosilanes with M_n 2200–51,500 in 34–94% yield, without any gel product. The refractive index (n_D) values of the polymers were consistent with the structures, and were in the range of 1.460–1.711. High refractive index of hyperbranched polymers is ascribed to high density resulting from the formation of microgel moieties in the main chains.

Two different strategies were investigated for the removal of residual Grubbs' third generation catalyst from polymers prepared by ROMP. A variety of heterogeneous functionalized particle scavengers and small molecule solubilizing agents were tested for the ability to reduce trace metal species relative to typical polymer purification methods. Residual catalyst levels of 10–120 ppm were achieved depending on a number of factors.

Acetals are found to produce efficient initiating radicals for free radical photopolymerization of acrylates, either as coinitiators in two-component photoinitiating systems or as substituent group linked to Type II photoinitiator.

Boronic acid end-functionalized polycaprolactone derivatives are efficiently converted into boroxine-core star polymer assemblies in the presence of N-donor Lewis bases. Postsynthetic modification of the nonboron end group was achieved via click chemistry. The dynamic covalent chemistry associated with the boronic acid end-group(s) makes these polymers attractive as macromolecular reagents.

Microwave enhancement of polymerization, temperature control and viscosity of the reaction media were closely related to provide a reasonable living/controlled synthesis of water-soluble homopolymer and block copolymer.

A new approach of using macroinitiator and ATRP to prepare isotactic polypropylene (i-PP)-based functional diblock copolymers was introduced. A metallocene-catalyzed polymerization process controlled by a consecutive chain transfer reaction with 1,2-bis(4-vinylphenyl)ethane and hydrogen rendered styryl-capped i-PP, which was facilely converted to i-PP terminated with a 1-chloroethylbezene group via a straightforward hydrochlorination reaction. This chlorine-bearing i-PP was able to effectively engage in ATRP polymerization to prepare functional i-PP diblock copolymers such as i-PP-b-PMMA.

A series of thermally stable aromatic polyimides (AZTA-PI)s containing triphenylamine and 1,2,4-triazole moieties were synthesized. A resistive switching device based on the solution processable polyimide (AZTA-PIa) exhibits nonvolatile and nonrewritable electrical bistability and fulfils the functionality of a write-once read-many times (WORM) memory. The WORM characteristics arise from the conformation-coupled charge transfer process induced by an applied electric field.

Poly(chlorotrifluoroethylene-alt-vinyl ether)-g-polystyrene bearing ammonium side groups were successfully prepared and characterized by consecutive polymerizations and modifications.

A series of novel low-bandgap triphenylamine-based conjugated polymers (PCAZCN, PPTZCN, and PDTPCN) consisting of different electron-rich donors in main chains were synthesized. The PSC device containing blend of donor PCAZCN and acceptor PC₇₁BM in 1:2 weight ratio showed the highest PCE value of 1.28% with V_oc = 0.81 V, J_sc = 4.93 mA/cm², and FF = 32.1%.

A series of poly(arylene ether ketone)s containing methoxy groups were synthesized by direct copolymerization method. After demethylation and sulfobutylation, poly(arylene ether ketone)s tethering sulfonic acid groups on aliphatic side chain were obtained. The properties of the side-chain-type sulfonated poly(arylene ether ketone)s, such as water uptake, proton conductivity, and methanol permeability, have been investigated in detail.

Three new ureidopyrimidinone(UPy)-functionalized chain-transfer agents (CTAs) have been synthesized for use in reversible addition-fragmentation chain transfer (RAFT) polymerization. These UPy-CTAs are able to polymerize a wide variety of vinyl monomers to yield UPy-functionalized polymers, including homopolymers, block copolymers and amphiphilic block copoiymers. An ω-functionalized (R group) UPy-CTA was used primarily for polymerizations as the resultant polymers will have a higher degree of UPY-functionalization. These polymers have been characterized via ¹H and ¹³C NMR spectroscopy, gel permeation chromatography (GPC), UV/visible spectroscopy and differential scanning calorimetry (DSC) to demonstrate end-group fidelity.

The surface-initiated SET-LRP of NIPAM in the presence of Cu(0) prepared in situ from the disproportionation of Cu(I) in a 2,2′-bpy/DMF system at 90 °C was conducted in a well-controlled manner, and obtained dense and homogeneous poly(NIPAM) brushes on the silicon wafer surface.

The thermal stability of thermoresponsive polymers may be strongly affected by the nature of the side chains present. Introduction of hydroxymethyl side chains into poly-N-isopropylacrylamide to alter the cloud point temperature decreases thermal stability of the solid polymer. This leads to degradation via water elimination to generate a modified polymer, probably containing imine functionality. The T_g of the modified polymer increases as the proportion of hydroxy side chains increases. This degradation limits the temperatures that can be used for processing of these polymers if the original (thermoresponsive) properties are to be retained.

A novel graft copolymer HPG with “Y”-shaped side chains PS-b-PEO₂ was synthesized by combining of ATRP and “click” methods. It was found that the efficiency of “click” chemistry was quite acceptable even if the density of side chains on HPG was rather high, and the structure of the graft copolymers could be well characterized by selective cleavage of the side chains.

Within these studies, an interesting combination of benzophenone-type sensitizers with oxime esters 1–3 as initiators was investigated on their efficiency to initiate the radical photopolymerization of (meth)acrylate-based formulations. Surprisingly, the reactivity of this combination was comparable to typical monomolecular photoinitiators like Darocur 1173 for acrylate monomers. Furthermore, sufficient thermal stability was proven by TGA and storage stability experiments of a resin formulation under elevated temperature.

Four novel 2-trifluoromethyl-activated bisfluoro monomers were synthesized successfully using a Suzuki-coupling reaction of 3-trifluoromethyl-4-fluoro phenyl boronic acid with 2,7-dibromofluorene with varied pendants. Four monomers were converted to a series of fluorene-based poly(arylene ether)s with pendants by nucleophilic displacement of the fluorine atoms on the terminal benzene ring with 4,4′-hexafluoroisopropylidenediphenol.

Ring-opening polymerization of 1,4-dioxan-2-one in bulk was initiated by three titanium alkoxides, titanium dichlorodiisopropoxide (TiCl₂(OiPr)₂), titanium chlorotriisopropoxide (TiCl(OiPr)₃), and titanium tetraisopropoxide (Ti(OiPr)₄). High conversion of monomer (90%) and high molecular weight (11.9 × 10⁴ g/mol) of resulting polymer can be achieved in only 5 min at 60 °C with Ti(OiPr)₄ as an initiator. Polymerization initiated by Ti(OiPr)₄ followed a first-order kinetics, with an apparent activation energy of 33.7 kJ/mol, which is significantly lower than earlier reported values with other catalysts, namely La(OiPr)₃ (50.5 kJ/mol) and Sn(Oct)₂ (71.8 kJ/mol).

Novel 5-Z-amino-δ-valerolactone (5-NHZ-VL) was easily synthesized in two steps with an aim to prepare a family of aliphatic polyesters having amino pendant groups. (5-NHZ-VL) was homopolymerized and copolymerized with ε-CL to generate copolyesters with an amino-group content ranging from 10 to 80%. Finally, the polyelectrolyte poly(5-NH₃⁺-VL) was recovered by removal of the protecting group under acidic conditions, and integrity of the polyester backbone was confirmed by ¹H NMR.

Fatty acid functionalized norbornenes were polymerized in a living fashion via ring opening metathesis for the first time. A commercially available norbornene was thus reacted with saturated fatty acids having different chain lengths (C₆–C₁₈). The derived partially renewable monomers were then polymerized in a living fashion and the properties of the resulting polymers were characterized. We thus demonstrated a new way to utilize fatty acids as a renewable feedstock in polymer science by taking advantage of the synthetic potential of nature.

New biobased, unsaturated and water-soluble polyesters from isosorbide, poly(ethylene glycol), and maleic anhydride have been developed. The chemical structure and molecular weight of the copolymers were confirmed by 2D NMR, titration and GPC methods. The synthesized polyesters exhibit good thermal stability and are therefore useful for many industrial applications.

A series of self-catalyzed imide-containing pthalonitrile polymers were synthesized. The structures and thermal properties of the polymers were investigated. Apart from high T_g values, they have high thermal stability and a large processing window.

Two main-chain polymers consisting of heteroarene-fused π-conjuagted donor moiety alternating with alternating with 4,7-bis(5-bromo-4-octylthiophen-2-yl)benzo[c][1,2,5]thiadiazole (P1) or 2,5-bis(5-bromo-4-octylthiophen-2-yl)thiazolo[5,4-d]thiazole (P2) units have been synthesized. The polymer (P1) has a broad absorption extending from 300 to 600 nm with optical bandgaps as low as 2.02 eV. The polymers were employed to fabricate organic photovoltaic cells with methanofullerene [6,6]-phenyl C71-butyric acid methyl ester. The polymer solar cell device containing P1 had the best preliminary results with a V_oc of 0.61 V, a J_sc of 6.19 mA/cm², and a fill factor of 0.32, offering an overall power conversion efficiency of 1.21%.

The incorporation of the bipolar side chains into the polymer structure prevented the intermolecular interaction of the fluorene moieties, balance charge injection/transport, and thereby improve the polymer backbone emission.

Heterogenization of metallocene catalyst using a silica support modified with a polyhedral silsesquioxane spacer (POSS) is described. For a range of POSS and metallocene concentrations, the activity for ethylene polymerization was close to that of the homogeneous catalyst while doubling the mass-average molar mass of the produced polymer.

Siloxane-containing polybenzoxazine prepolymers with high molecular weight were prepared from bisphenol-A, diaminopolysiloxane, and paraformaldehyde. Free standing prepolymer films with high transparency were easily obtained by casting the prepolymer solutions on glass plates. Heat treatment of the prepolymer films up to 240 °C gave brown transparent siloxane-containing polybenzoxazine films. The novel polybenzoxazine films exhibited significantly improved toughness and high thermal stability due to the polysiloxane component and long linear backbone.

New 2-oxazolines containing S-galactosyl substituents were prepared. Using a 1:1 adduct of 2-methyl-2-oxazoline and MeOTf, as the initiator, the monomer was polymerized via ring-opening homo- and copolymerization and subsequent deprotection gave poly(2-oxazoline)s having pendant carbohydrate. The interaction with RCA₁₂₀ lectin was investigated, the binding constant was increased compared with D-galactose. The in vivo expression of green fluorescent protein using the synthesized poly(S-glycooxazoline)s as polymeric inducers in E. coli host were performed.

Water-soluble fluorescent copolymer PPNEu was successfully synthesized by free radical copolymerization in methanol with AIBN as initiator. TEM observation showed that the PPNEu could form spherical micelles in water solution small than 100 nm; the efficient complexation of PPNEu with DNA occurred. The results of fluorescence, UV-vis absorption, and agarose electrophoresis indicated that the PPNEu could interact with DNA in an electrostatic bonding mode.

Three-component polyaddition of diamines, carbon disulfide, and diacrylates in an aqueous/organic biphasic medium produced a poly(dithiourethane-amine) with a high proportion of dithiourethane units almost quantitatively. The resulting poly(dithiourethane-amine)s exhibited high adsorption selectivity for Pd (II), due to the high affinity of the thiocarbonyl sulfur atoms for soft metal ions. This polymer is expected to be useful as a selective rare-metal adsorbing material.

To avoid time-consuming separation procedure, two-step ring-opening polymerization of ethylene oxide was utilized to synthesize “umbrella-like” PEG for protein conjugation instead of coupling methods. Through the novel strategy, we can easily obtain monofunctional-branched PEG of high purity, which was a good technique for the production of PEG for medicinal uses.

Anthracene-functionalized oxanorbornene monomer and oxanorbornenyl polystyrene with ω-anthracene end-functionalized macromonomer were first polymerized via ring-opening metathesis polymerization using the first-generation Grubbs' catalyst in dichloromethane at room temperature and then clicked with maleimide end-functionalized polymers, poly(ethylene glycol) (PEG)-MI, poly(methyl methacrylate) (PMMA)-MI, and poly(tert-butyl acrylate) (PtBA)-MI in a Diels–Alder reaction in toluene at 120 °C to create corresponding graft copolymers, poly(oxanorbornene)-g-PEG, poly(oxanorbornene)-g-PMMA, and graft block copolymers, poly(oxanorbornene)-g-(PS-b-PEG), poly(oxanorbornene)-g-(PS-b-PMMA), and poly(oxanorbornene)-g-(PS-b-PtBA), respectively.

Novel organotin-containing core-cross-linked knedels and shell-cross-linked knedels were synthesized facilely from poly(styrene)-b-poly(acrylate acid) nanoparticles by using organotin compound 1,3-dichloro-tetra-n-butyl-distannoxane as cross-linker. Transmission electron microscopy study showed the spherical morphology and the size of the cross-linked knedels. The organotin-containing core-cross-linked knedel can be used as catalyst to more efficiently realize the aqueous esterification reactions.

Poly(anhydride-esters) based on 5-aminosalicylic acid (5-ASA) were synthesized via solution polymerization. This polymerization method produced polymers with higher molecular weights and better solubility in organic solvents, relative to polymers produced by melt condensation polymerization. Three synthetic steps were required to introduce 5-ASA into polymers via biodegradable bonds such as esters. By changing the alkyl lengths of either the amine protecting group or linkage between 5-ASA units, a range of 5-ASA-based polymers with varying glass transition temperatures, molecular weights, and solubilities in low-boiling organic solvents were prepared.

Polystyrene-bound uniform linear oligoethers, where each repeating unit bears a functional arm, were prepared by stepwise solid-phase synthesis. These oligomeric spacers are an alternative to dendritic oligoethers and preserve the multivalent nature of the latter. L-Proline, immobilized on the support equipped with such oligomeric spacers, induced in the model aldol reaction activity and selectivity, comparable to those of the proline immobilized on a related dendronized support. The functional side chains of the oligoethers can be dendronized, thus increasing, even more, the local density of the functional groups near each attachment site on the polystyrene matrix.