Synthesis and characterization of side-chain liquid-crystalline block-copolymers containing laterally attached photoluminescent quinquephenyl units via ATRP

A series of novel side-chain liquid-crystalline polymers (SCLCPs) consisting of laterally attached photoluminescent p-quinquephenyl (QQP) pendants with different flexible terminal- and/or side-alkoxy chains were synthesized via atom transfer radical polymerization (ATRP). Homopolymers (HP1-HP3) and block-copolymers (PSP1-PSP3 and PEOP1-PEOP3), where QQP units were copolymerized with styrene or ethylene oxide monomers, possessed the number average molecular weights (M_n) of 8.7-26.0 × 10³ with narrow PDI values of 1.08-1.26. Various characterization techniques of polarized optical microscopy (POM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD) were used to investigate their mesomorphic properties, and all homopolymers and block-copolymers exhibited the nematic phase affected by the flexible terminal- and/or side-alkoxy chains of the conjugated rod-like pendants. In addition, the photophysical properties of these polymers were measured by UV-vis and photoluminescence (PL) spectroscopies, which showed blue PL emissions with rather high fluorescence quantum yields in solutions.     

Synthesis of well-defined star polymers and star block copolymers from dendrimer initiators by atom transfer radical polymerization

Novel polyarylether dendrimers with 1,3,5-tri(4-hydroxyphenoxy)benzene core, polybenzylether interior, and benzyl 2-bromoisobutyrate surface group (CMGn-Br, n=1-3, with functionality of 6, 12, and 24, respectively) were prepared by convergent procedure. ATRP of tert-butyl acrylate (tBA) and styrene (St) with CMGn-Br dendrimer initiators in the presence of CuBr/pentamethyldiethylenetriamine catalytic system was investigated in detail, and a series of well-defined dendrimer-like star PtBA and PSt with precise arm numbers were synthesized under suitable conditions. The quantitative initiation of the dendrimer initiators was demonstrated by high initiation efficiency, ¹H NMR spectra, hydrolysis, and MALLS/SEC approach. Star block copolymers comprising PSt and PtBA segments with low polydispersity (1.08<M_w/M_n<1.18) were also successfully synthesized using functional macroinitiators by block copolymerization. In addition, the thermal properties of the resultant polymers were characterized by DSC and TGA.     

Star polymers synthesised with flexible resorcinarene-derived ATRP initiators

Two octafunctional resorcinarene-based ATRP initiators were synthesised where the initiating sites were separated from the macrocyclic ring with a short spacer. The spacer was introduced to reduce the steric hindrance at the initiating sites and to increase the number of arms in the resulting star polymers. Higher functionalities of starlike poly(tert-butyl acrylates), PtBA, and poly(methyl methacrylates), PMMA, were obtained, compared to the results by the initiators without a spacer. The kinetics of the polymerisations of tBA and MMA were investigated using various catalysts and solvents. The spacer increased the rate of the polymerisation of bulkier tBA monomer, but had little effect on the polymerisation of MMA.     

One-pot synthesis of star polymer by ATRP of bismaleimide and an excess of styrene with a conventional initiator

A pragmatic one-pot approach to the synthesis of star polymers is reported using atom transfer radical copolymerization (ATRcP) of a bismaleimide and an excess of styrene (St) initiated with a conventional ATRP initiator.     

An all ATRP route to PMMA-PEO-PS and PMAA-PEO-PS miktoarm ABC star terpolymer

An all Atom Transfer Radical Polymerization (ATRP) route to synthesize miktoarm ABC star terpolymer, μ-(poly(methyl methacrylate)-poly(ethylene oxide)-polystyrene) (μ-(PMMA-PEO-PS)), was demonstrated. Poly(methyl methacrylate) (PMMA) with a halide end group was first prepared by ATRP of MMA. It was then activated under ATRP conditions at 30 °C to add a styrenic-terminated PEO macromonomer, resulting in the formation of PMMA-b-PEO. Finally, the active halide at the junction point of the diblock copolymer was used to initiate the ATRP of St at higher temperature. By a similar approach, μ-(poly(phenyl methacrylate)-poly(ethylene oxide)-polystyrene) (μ-(PhMA-PEO-PS)) was synthesized, hydrolysis of which in basic medium gave μ-(PMAA-PEO-PS). The polymers were characterized by ¹H NMR spectroscopy and gel permeation chromatography.     

ATRP poly(acrylate) star formation: A comparative study between MALDI and ESI mass spectrometry

Optimised matrix-assisted laser desorption/ionisation (MALDI) and electrospray ionisation (ESI) mass spectrometry (MS) methodologies were systematically compared in terms of their relative abilities to identify distinct chemical species present in samples associated with a polymer mechanistic study. In order to perform the investigation, formation processes involved in atom transfer radical polymerisation (ATRP) mediated methyl acrylate (MA) star polymerisations were studied. In addition to the 4-armed ATRP initiator employed in the polymerisations, initiator side-products were found to generate oligomeric chains. At a relatively high monomer to polymer conversion, terminal Br loss was observed in these oligomers; this Br loss was hypothesised to occur via degradative transfer reactions involving the radicals (CH₃)₂?OH, ?H₃ and ?H₂COCH₃, which were derived from the acetone used as a solvent in the polymerisations, as well as hydrogen radicals donated by the ligand N,N′,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA). In performing these studies, ESI was found to identify a greater number of distinct chemical species in the samples under investigation when compared to the employed MALDI technique, suggesting that the utilisation of ESI must be strongly considered in polymer mechanistic investigations if the maximum number of end-group functionalities within a given polymer sample are to be identified.     

Alkylation of polyethyleneimine for homogeneous ligands in ATRP

Ethylated and butylated polyethyleneimine ligands were synthesized and employed in copper catalyzed atom transfer radical polymerization of styrene and methyl methacrylate with suitable initiators in order to obtain homogeneous polymerizations, resulting in well defined polymers with low polydispersities. Linear curves drawn from kinetics and conversion-molecular weight plots indicate that all the polymerizations were successfully controlled. In ATRP reactions of S and MMA, the apparent rate of polymerization, k_p^app, exhibits a plateau at [Ligand]/[CuBr] ≥ 0.5 ratio for both ligands. The apparent rate constant also decreases by increasing the alkyl chain length of the alkylated polyethyleneimine ligand. Ethylated and butylated polyethyleneimine ligands in ATRP of S and MMA were found to be faster than the existing ATRP ligands.     

Synthesis,characterization, and property of end-functionalized telechelic PST via ATRP

Polystyrene incorporating carboxylate group as α-end was synthesized by using initiator 4-chloromethyl benzoic acid via atom transfer radical polymerization. Its ω-chlorine end-group was transformed by cumic acid, diethyl malonate, and thiol, respectively, to form end-functionalized telechelic polystyrenes. These PSts with different functionalized ω-end group (PSt 1 , PSt 2 , and PSt 3) were obtained and characterized by H NMR and TGA. This type of end-functionalized telechelic polymers can further act as polymeric ligands to form polymeric metal complexes. In this study, PSt 1 with carboxylate group at each end was allowed to react with Eu(DBM)₂Cl·2H₂O to afford a new polymeric complex PSt 1 -Eu(III) showing significant red-light emission. Moreover, the film of PSt 1 -Eu shows similar emission pattern with its DMF solution. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

功能离子液体[N4MIM]Cl的合成及其配合Cu 催化ATRP反应研究

以N-甲基咪唑为骨架引入1,2-二氯乙烷合成中间体氯化1-氯乙基-3-甲基咪唑([CeMIM]Cl),再与三乙烯四胺反应合成了氯化1-（三乙基四氨基）乙基-3-甲基咪唑离子液体（[N4MIM]Cl）。通过红外光谱IR、核磁共振氢谱1HNMR对[N4MIM]Cl进行分析测试,确证了[N4MIM]Cl的化学结构。通过循环伏安法测得[N4MIM]Cl具有较低的氧化还原电势,E1,2为-0.472V,与有机配体相比[N4MIM]Cl具有较好的配位性能。将[N4MIM]Cl与CuBr配位用于催化氯化1-烯丙基-3-甲基咪唑离子液体（[AMIM]Cl）体系中甲基丙烯酸甲酯（MMA）的原子转移自由基聚合（ATRP）反应,经凝胶渗透色谱法（GPC）测试证明[N4MIM]Cl对ATRP反应具有较好的可控性。原子吸收光谱（AAS）测定聚合产物聚甲基丙烯酸甲酯（PMMA）中Cu2 的残留量仅为360mg穔g-1,表明与传统有机配体相比,[N4MIM]Cl有利于催化剂与聚合产物的分离。     

Synthesis and properties of novel macromolecular coupling agents prepared by ATRP

Novel block and graft macromolecular coupling agents with well‐defined structures have been synthesized successfully by atom transfer radical polymerization (ATRP). The molecular weights and molecular weight distributions of those functional copolymers can be controlled because of the living/controlled ATRP. The structures and composition of block and graft copolymers with the monomers of butyl acrylate (BA), styrene (St), and 3‐methacryloxyl‐propyltrimethoxyl silicon (KH‐570) have been characterized by mean of ¹H NMR, IR, GPC, and UV. Because the KH‐570 of macromolecular coupling agents owns strong affinity to surface hydroxyl of fillers, inorganic fillers that were treated by the macromolecular coupling agents possess some new properties, for example increasing the effect between matrix and fillers of composites. The mechanical properties and morphology of composites with macromolecular coupling agents have been investigated by the dynamic mechanical spectra and SEM. The results showed that the damping value and compatibility of composites with macromolecular coupling agents were improved greatly when compared with that of composite with small molecular coupling agent. Furthermore with different contents of BA, St, and KH‐570 in the macromolecular coupling agents, the damping value of the composites are different. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3919–3926, 2006     

Octadecyl acrylate - Methyl methacrylate block and gradient copolymers from ATRP: Comb-like stabilizers for the preparation of micro- and nano-particles of poly(methyl methacrylate) and poly(acrylonitrile) by non-aqueous dispersion polymerization

Three random and three block copolymers of methyl methacrylate (MMA) and octadecyl acrylate (ODA) were synthesized by atom transfer radical polymerization. These copolymers were assessed for their application as stabilizers in the one-step non-aqueous dispersion (NAD) polymerization of MMA and of acrylonitrile (AN) in a non-polar solvent mixture of hexane and dodecane. In all cases stable spherical micro-particle colloidal dispersions were formed with particle diameters in the range of 62-2725 nm for PMMA. Uniform monodisperse PMMA particles with standard deviations in size distributions of less than 5% were obtained in two cases demonstrating the utility of ODA:MMA copolymers as replacement preformed stabilizers in the one-step synthesis of MMA micro-spheres. Overall the block copolymer PMMA₆₄-block-PODA₃₆ gave greater control over size when varying the solvent:monomer ration than a related gradient PMMA-PODA copolymer. These copolymers were further used as stabilizers in the one-step NAD polymerization of MMA with ethylene glycol dimethacrylate (EGDMA) under similar conditions allowing for the preparation of monodisperse cross-linked PMMA particles with diameters ranging from 110 to 1700 nm. The general utility of the copolymers as stabilizers was demonstrated by the NAD polymerization of acrylonitrile (AN) in non-polar solvent mixture of hexane and dodecane giving ‘crumpled’ latex dispersions with particle diameters in the range 85-483 nm.     

Initiator efficiency in ATRP: the tosyl chloride/CuBr/PMDETA system

The low efficiency of p-toluenesulfonyl chloride (TsCl) initiator for the polymerization of methyl methacrylate (MMA), when used in conjunction with N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA) and CuBr under atom transfer radical polymerization (ATRP) conditions was investigated. A major by-product in the formation of poly(methyl methacrylate) was identified as N,N-dimethyl-p-toluenesulfonamide (5) and accounted for approximately half of the initiator. Compound 5 was shown to form by the direct reaction of PMDETA and TsCl. In a model experiment equimolar amounts of TsCl, PMDETA and CuBr reacted at 80°C in p-xylene resulted in the formation of 5 and two other unsaturated sulfones 2-methyl-3-[(4-methylphenyl)sulfonyl]-2-propenoic acid methyl ester (6) and 2-[[4-methylphenyl)sulfonyl]methyl]-2-propenoic acid methyl ester (7), formed by the dehydrohalogenation and subsequent isomerization of an intermediate chloro-adduct, 1-(4-methylbenzenesulfonyl)-2-chloro-2-(methyl)methyl propionate (2). Molecular modeling predicted the unsaturated sulfone 7 was thermodynamically more stable than the higher conjugated sulfone 6 and this was confirmed by the isomerization of 6 to 7 at room temperature under mild basic conditions. The absence of 6 and 7 in the polymerization of MMA under ATRP conditions showed that in the early stages of polymerization in the presence of excess MMA, the intermediate chloro-adduct 2 is not formed.     

Synthesis of block copolymers for surface functionalization with stimuli-responsive macromolecules

Using block copolymers with poly(n-butyl acrylate) (PBA) as anchor block being capable to tether the temperature-responsive block poly(N-isopropylacrylamide) (PNIPAAm) to the surface, polysulfone (PSf) films were functionalized applying an adsorption/surface entrapment process. Homo and block copolymer synthesis was investigated applying atom transfer radical polymerization (ATRP) using tris(2-(dimethylamino)ethyl)amine (Me₆TREN), CuCl and N,N-dimethylformamide (DMF). On basis of the determined critical micelle concentration of the block copolymers, surface functionalization of PSf was performed from an aqueous solution containing 25 vol% dimethylacetamide. These functionalized surfaces exhibit reversible temperature dependent properties due to the lower critical solution temperature (LCST) of PNIPAAm as can be proven by contact angle measurement. Furthermore, the beneficial effect of the PBA block with adjusted molecular weight on the stability of these coatings was proven. This surface functionalization method has various potential applications and the resulting surfaces are anticipated to exhibit actively triggerable ‘chaotic’ properties as basis of an efficient anti-biofouling strategy.     

A novel amphiphilic AB2 star copolymer synthesized by the combination of ring-opening metathesis polymerization and atom transfer radical polymerization

A new amphiphilic AB₂ star copolymer was synthesized by the combination of ring-opening metathesis polymerization (ROMP) and atom transfer radical polymerization (ATRP). Two different routes (methods A and B) were employed firstly to prepare the poly(oxanorbornene)-based monotelechelic polymers as the hydrophobic arm bearing dibromo-ended group via ROMP in the presence of two different terminating agents catalyzed by first generation Grubbs catalyst. The values of capping efficiency (CE) of the polymers were determined by NMR, which were 94% and 67% for methods A and B, respectively. Then, the dibromo-ended ROMP polymers were used as the macroinitiators for ATRP of 2-(dimethylamino)ethyl methacrylate (DMAEMA) to produce two hydrophilic arms. The prepared amphiphilic AB₂ star copolymers poly(7-oxanorborn-5-ene-exo,exo-2,3-dicarboxylic acid dimethyl ester)-block-bis[poly(2-(dimethylamino)ethyl methacrylate)] (PONBDM_n-b-(PDMAEMA_m)₂) with a fixed chain length of hydrophobic PONBDM and various hydrophilic PDMAEMA chain lengths can self-assemble spontaneously in water to form polymeric micelles, which were characterized by dynamic light scattering, atom force microscopy, and transmission electron microscopy measurements.     

Preparation of hyperbranched copolymers of maleimide inimer and styrene by ATRP

Novel hyperbranched copolymers were prepared by the atom transfer radical copolymerization of N-(4-α-bromobutyryloxy phenyl) maleimide (BBPMI) with styrene in 1-methyl-2-pyrrolidone (NMP) using the complex of CuBr/2,2′-bipyridine as catalyst. The copolymerization behavior was investigated by comparison of the conversion of double bond of BBPMI determined by ¹H NMR with that of styrene. The hyperbranched structure of resulting copolymers was verified by gel permeation chromatography (GPC) coupled with multi-angle laser light scattering (MALLS). The influences of dosage of catalyst and monomer ratio on the polymerization rate and structure of the resulting polymers were also investigated. The glass transition temperature of the resulting hyperbranched copolymer increases with increasing mole fraction of BBPMI, f_BBPMI. The resulting copolymers exhibit improved solubility in organic solvents; however, they show lower thermal stabilities than their linear analogues.     

Modification of carbon nanotubes with well-controlled fluorescent styrene-based polymers using the Diels-Alder reaction

A simple and single-step “grafting to” approach based on the Diels-Alder (DA) reaction is described to functionalize multi-wall carbon nanotubes (MWCNTs) with polystyrene (PSt). Thus, several fluorescent and furfuryl functionalized PSts, synthesized by the atom transfer radical polymerization (ATRP) of styrene, furfuryl methacrylate and low proportion of a fluorescent monomer, were covalently attached onto the pristine nanotubes. Furfuryl (diene) groups allowed the chemical attachment of the PSt polymer onto the as-synthesized MWCNTs by a DA reaction. On the other hand, the incorporation of fluorescent groups in the polymer has two main advantages. It permits to determine the attachment of the polymer onto the nanotubes and, in further applications, it will allow to follow the dispersion of these modified MWCNTs in a matrix. The efficiency of the functionalization was verified by FTIR, Raman spectroscopy, TEM, AFM and fluorescence techniques.     

Preparation of onion-like multilayered particles comprising mainly poly(iso-butyl methacrylate)-block-polystyrene by two-step AGET ATRP

Synthesis of multilayered composite polymer particles comprising mainly poly(iso-butyl methacrylate)-block-polystyrene (PiBMA-b-PS) has been carried out by the use of two-step activator generated by electron transfer for atom transfer radical polymerization (AGET ATRP) in aqueous microsuspension. PiBMA-Br macroinitiator seed particles were prepared in the first step, followed by swelling with styrene and second step (seeded) polymerization. The blocking efficiency in the second step was found to be crucial with regards to the resulting particle morphology. A disordered sea-island morphology was obtained when the blocking efficiency was 47% (73% conversion), whereas a blocking efficiency of 61% (71% conversion) resulted in the formation of multilayered particles. High blocking efficiency can be achieved by careful adjustment of the activation rate by proper choice of polymerization temperature and amount of reducing agent (ascorbic acid).     

Synthesis of well‐defined glycoconjugate polyacrylamides via preactivated polymers prepared by ATRP

Poly(N‐acryloxysuccinimide) (polyNAS) with narrow molecular weight distributions (MWD) applicable for the preparation of well‐defined glycoconjugate polyacrylamides were successfully prepared by atom transfer radical polymerization (ATRP). The structures of polyNAS were characterized by ¹H‐NMR and GPC. GPC results showed that the molecular weight polydispersity indices (PDI) range from 1.17 to 1.29. The molecular weights could be calculated based on ¹H‐NMR results but GPC results of polyNAS by using 0.01M LiBr/DMF did not give accurate molecular weights, probably because of the complex interaction in the system. The effects of free N‐hydroxysuccimide produced in the polymerization processes on the free‐radical concentrations and apparent initiation efficiencies of ATRP were discussed. Well‐defined glycoconjugate polyacrylamides (i.e., with narrow molecular weight distributions and designed glycoconjugate degrees) were prepared by substituting N‐oxysuccimide units with galactosamine followed by reaction of ethanolamine. The galactose conjugate degrees were determined by ¹H‐NMR and the total substitutions of N‐oxysuccimides were verified by ¹H‐NMR and FTIR. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 189–194, 2005     

Synthesis and characterization of four-armed star mesogen-jacketed liquid crystal polymer

The synthesis of four-armed star mesogen-jacketed liquid crystal polymer was achieved by atom transfer radical polymerization in chlorobenzene solution using pentaerythritol terakis(2-bromoisobutyrate) (PT-Br) as an initiator and CuBr/sparteine complex as a catalyst. The results show that the number average molecular weigh is creased linearly vs. monomer conversion, and that the polydispersities were quite narrow (<1.19), which is the character of controlled polymerization. The structure was experimentally confirmed by ¹H NMR. The liquid-crystalline behavior of the four-armed star polymer was studied using DSC and POM. Only the polymer with a M_n,GPC beyond 3.68×10⁴ g/mol formed a liquid crystalline phase which was quite stable with a high clearing point.     

对甲氧基偶氮苯星形聚合物的合成与表征

利用原子转移自由基聚合(ATRP)技术合成了对甲氧基偶氮苯星形聚合物。均苯三酚与2-溴异丁酰溴通过酯化反应得到三官能团引发剂,引发对甲氧基偶氮苯单体6-[4-(4-甲氧基苯基偶氮)酚氧基]己基甲基丙烯酸酯(MMAzo)的ATRP反应。表征了星形聚合物结构、热行为与液晶性,显示其与线性均聚物的液晶性相似,均显示近晶相和向列相,但其相转变温度有所降低。