Synthesis and characterization of H-type amphiphilic liquid crystalline block copolymers by ATRP

H-type amphiphilic liquid crystalline block copolymers containing azobenzene were synthesized by atom transfer radical polymerization （ATRP）. Macroinitiators prepared by the esterification between poly（ethylene oxide） （PEG） and 2,2-dichloroacetyl chloride were utilized to initiate the polymerization of 6-[4-（4-ethoxyphenylazo）phenoxy]hexyl rnethacrylate （M6C）. The resulting macroinitiators and block copolymers were characterized by ^1H NMR, gel permeation chromatography （GPC）. Polarizing optical microscopy （POM） and differential scanning calorimetry （DSC） preliminarily revealed the liquid crystalline property of these block copolymers. This series of liquid crystalline block copolymers are promising in some areas, such as optical data storage, optical switch, and molecular devices.     

Morphology study of a series of azobenzene-containing side-on liquid crystalline triblock copolymers

A series of azobenzene containing side-on liquid crystalline ABA triblock copolymers were investigated.This triblock series possesses the same central liquid crystal block B and various lengths of the amorphous block A.Transmission electron microscopy(TEM),small angle X-rays and neutron scattering(SAXS and SANS) were used to study their morphologies.After annealing the samples over weeks at a temperature within the nematic temperature range of block B, different morphologies(disordered,lamellar,perforated layer and hexagonal cylinder) were observed by TEM.The alignment behavior of these azo triblock copolymers in the magnetic field for artificial muscle application,as well as the phase period and the order-disorder transition(ODT) were studied in situ by SANS.     

Synthesis of novel multi-arm star azobenzene side-chain liquid crystalline copolymers with a hyperbranched core

A series of novel multi-arm star side-chain liquid crystalline (LC) copolymers with hyperbranched core moieties were synthesized by atom transfer radical polymerization (ATRP) using a multi-functional hyperbranched polyether as the initiator and chlorobenzene as the solvent. The multi-functional hyperbranched polyether initiator was prepared from poly(3-ethyl-3-(hydroxymethyl)oxetane) (PEHO) and 2-bromo-2-methylpropionyl bromide. The azobenzene side-chain liquid crystalline arms were designed to have an LC conformation of poly[6-(4-methoxy-4^′-oxy-azobenzene)hexyl methacrylate] with different molecular weights. Their characterization was performed with ¹H NMR, size exclusion chromatograph (SEC), differential scanning calorimetry (DSC) and thermal polarized optical microscopy (POM). The multi-arm star side-chain liquid crystalline copolymers exhibited a smectic and a nematic phase, and the phase transition temperatures from the smectic to the nematic phase and from the nematic to isotropic phase increased with increasing the molecular weight of the multi-arm star side-chain liquid crystalline copolymers from 1.78 × 10⁴ to 9.07 × 10⁴.     

Synthesis of PDMAEMA-PCL-PDMAEMA triblock copolymers

The synthesis of ABA triblock copolymers of the type PDMAEMA-PCL-PDMAEMA was achieved by atom transfer radical polymerization (ATRP) of DMAEMA using difunctional polycaprolactone (PCL) as macroinitiator. First, ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) was carried out in the presence of 1,2-diaminoethane/tin (II) octanoate. Dihydroxy PCL thus obtained was end-functionalized in a quantitative manner using 2-bromoisobutyryl bromide. The resulting Br-PCL-Br was used as macroinitiator in the ATRP of DMAEMA leading to triblock copolymers with PCL as the central block and PDMAEMA sequences of different lengths. NMR and SEC analyses confirmed the formation of ABA triblocks.     

Electroluminescent block copolymers containing oxadiazole and thiophene via ATRP

Block copolymers containing thiophene units in one block and oxadiazole (OXD) units in the other were prepared. Atom transfer radical polymerization method was used to obtain the thiophene‐containing mesogen‐jacketed polymers, and the kinetic study indicated that the polymerization was controllable and the polymers could be used to initiate the polymerization of the OXD‐containing monomers. Photoluminescent spectra indicated that the fluorescence quantum yields of the polymers increased with increasing content of OXD. And, more OXD domains, that is, more interfaces between the hole‐transport parts and electron‐transport parts, resulting in the higher probability of exciplex formation. The electroluminescent devices containing the block copolymer with 64 mol % OXD as the emissive layer had a maximum brightness of 127 cd/m² and an extremely low onset voltage of 7.7 V, which indicated that the injection and transport of charge carriers were facilitated and the number of charge carriers was sufficiently high in early time after the voltage was turned on. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Y-shaped block copolymers of poly(ethylene glycol) and poly(N-isopropylacrylamide) synthesized by ATRP

Novel Y-shaped block copolymers of poly(ethylene glycol) and poly(N-isopropylacrylamide),PEG-b-(PNIPAM)_2,were successfully synthesized through atom transfer radical polymerization(ATRP).A difunctional macroinitiator was prepared by esterification of 2,2-dichloroacetyl chloride with poly(ethylene glycol) monomethyl ether(PEG).The copolymers were obtained via the ATRP of N-isopropylacrylamide(NIPAM) at 30℃with CuCl/Me_6TREN as a catalyst system and DMF/H_2O(v/v = 3:1) mixture as solvent.The resulting copo...     

Effect of the terminal substituent of azobenzene on the properties of ABA triblock copolymers via atom transfer radical polymerization

The effect of the terminal substituent of azobenzene on the properties of ABA triblock copolymers was investigated. For this study, three kinds of azobenzene‐containing monomers with different terminal substituents—6‐[4‐(4‐methoxyphenylazo)phenoxy] hexyl methacrylate, 6‐[4‐(4‐ethoxyphenylazo)phenoxy]hexyl methacrylate, and 6‐[4‐(4‐nitrophenylazo)phenoxy]hexyl methacrylate—were used to synthesize ABA triblock copolymers PMMAzo₂₅–PEG₁₃–PMMAzo₂₅/PMMAzo₁₂–PEG₁₃–PMMAzo₁₂, PEMAzo₁₄–PEG₁₃–PEMAzo₁₄, and PNMAzo₁₄–PEG₁₃–PNMAzo₁₄, respectively, by atom transfer radical polymerization (PMMAzo is poly{6‐[4‐(4‐methoxyphenylazo)phenoxy]hexyl methacrylate}, PEMAzo is poly{6‐[4‐(4‐ethoxyphenylazo)phenoxy]hexyl methacrylate}, and PNMAzo is poly{6‐[4‐(4‐nitrophenylazo)phenoxy]hexyl methacrylate}). These copolymers were characterized with ¹H NMR spectroscopy and gel permeation chromatography and exhibited controlled molecular weights and narrow molecular weight distributions. Differential scanning calorimetry and polarizing optical microscopy showed that these copolymers had mesophases. PMMAzo₂₅–PEG₁₃–PMMAzo₂₅ and PMMAzo₁₂–PEG₁₃–PMMAzo₁₂ had a smectic mesophase and a nematic mesophase, whereas both PEMAzo₁₄–PEG₁₃–PEMAzo₁₄ and PNMAzo₁₄–PEG₁₃–PNMAzo₁₄ had a nematic mesophase. This demonstrated that the liquid‐crystalline properties of these copolymers highly depended on the terminal substituent of azobenzene. The photoresponsive behavior of these copolymers was also investigated in tetrahydrofuran solutions, and the influence of the terminal substituents attached to azobenzene was studied. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5190–5198, 2007     

一种含乙氧羰基偶氮苯液晶三嵌段共聚物的合成与表征

利用原子转移自由基聚合(ATRP),合成了一种含有乙氧羰基偶氮苯的液晶三嵌段共聚物,并合成了一种同样偶氮生色团的均聚物进行对比.均聚物(PC6ET)由偶氮单体甲基丙烯酸{6-[4-(4-乙氧羰基苯基偶氮)苯氧基]己酯}(C6ET)的ATRP反应制备.嵌段共聚物的合成,先通过聚环氧乙烷(PEO)和过量的2-溴异丁酰溴、三乙胺反应,得到双端大分子引发剂(Br-PEO-Br);再进一步通过C6ET的ATRP反应,得到了三嵌段共聚物(PC6ET-PEO-PC6ET).热分析、偏光显微镜观察和X射线衍射实验证实,合成的均聚物和嵌段共聚物均为近晶型液晶聚合物.三嵌段共聚物的液晶清亮点比均聚物的稍低.     

ATRP of MMA initiated by 2-bromomethyl-4,5-diphenyloxazole at room temperature and study of fluorescent property

Atom transfer radical polymerization (ATRP) of MMA was conducted successfully at ambient temperature (25 °C) using 2-bromomethyl-4,5-diphenyloxazole as initiator, CuBr/2,2′-bipyridine (BPY) as catalyst, and 1,4-Dioxane as solvent. Factors such as the reaction temperature, mole ratio of monomer and catalyst to initiator, solvent and so on, which can affect the ATRP system, were discussed in the paper. Chain extension was conducted using polymer as the macro-initiator which was characterized via ¹H NMR. The optical property of initiator was well preserved in the obtained PMMA, and the end-functionalized PMMA exhibited obvious fluorescent emission at 367 nm.     

利用酶促开环聚合和原子转移自由基聚合方法合成AB型嵌段共聚物

我们用端基官能化方法实现两种聚合反应的结合, 成功地制备了AB型双嵌段共聚物PCL-b-PSt和BAB型三嵌段共聚物PSt-b-PCL-b-PSt. 本文利用上述方法, 将酶促开环聚合和原子转移自由基聚合有机地结合起来, 合成了AB型嵌段共聚物-聚己内酯/聚甲基丙烯酸环氧丙酯(PCL-b-PGMA. 此嵌段共聚物具有良好的生物相容性, 在现代生物领域具有广泛的应用前景.     

酶促缩聚和原子转移自由基聚合法合成AB型两亲性嵌段共聚物

Novozyme-435催化10-羟基癸酸进行自缩聚反应得到线性聚酯, 端基分别是羟基(—OH)和羧基(—COOH), 在三乙胺催化下, 分别用α-溴代丙酰溴和三甲基氯硅烷(TMSCL)进行端基官能化生成一个单官能度的大分子引发剂, 在CuCl/2,2'-联吡啶(bpy)催化体系中, 引发甲基丙烯酸环氧丙酯(GMA)的原子转移自由基反应(ATRP), 得到聚(10-羟基癸酸酯)/聚甲基丙烯酸环氧丙酯(PHDA-b-PGMA) AB 型两亲性嵌段共聚物, 其结构及分子量(分布)通过核磁共振和凝胶渗透色谱(GPC)确证. 此AB型两亲性嵌段共聚物在水溶液中能自组装形成纳米粒子, 用原子力显微镜(AFM)观察粒子的形状和大小.     

Synthesis and characterization of well‐defined ABC‐type triblock copolymers via atom transfer radical polymerization and stable free‐radical polymerization

An asymmetric difunctional initiator 2‐phenyl‐2‐[(2,2,6,6 tetramethylpiperidino)oxy] ethyl 2‐bromo propanoate ( 1 ) was used for the synthesis of ABC‐type methyl methacrylate (MMA)‐tert‐butylacrylate (tBA)‐styrene (St) triblock copolymers via a combination of atom transfer radical polymerization (ATRP) and stable free‐radical polymerization (SFRP). The ATRP‐ATRP‐SFRP or SFRP‐ATRP‐ATRP route led to ABC‐type triblock copolymers with controlled molecular weight and moderate polydispersity (M_w/M_n < 1.35). The block copolymers were characterized by gel permeation chromatography and ¹H NMR. The retaining chain‐end functionality and the applying halide exchange afforded high blocking efficiency as well as maintained control over entire routes. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2025–2032, 2002     

ATRP法合成弹性蛋白接枝共聚物及其性能研究

弹性蛋白经α-溴异丁酰溴化制备了大分子ATRP引发剂溴化弹性蛋白(E-Br), 再以E-Br作为引发剂, 在CuCl/2,2-联吡啶催化体系下, 用原子转移自由基聚合方法合成了弹性蛋白-g-聚甲基丙烯酸-β-羟乙酯接枝聚合物. 用红外光谱(FTIR)、X射线光电子能谱(XPS)、热重分析(TGA)、扫描电镜(SEM)、离子色谱和动态接触角对接枝聚合物进行了表征. 结果表明, PHEMA键接到了弹性蛋白表面; SEM显示接枝改性后弹性蛋白的表面比未改性前光滑, 但改性后样品的热性能均比未改性样品的低, 起始热分解温度由改性前的307 ℃变为265 ℃; 动态接触角实验结果表明, 接枝改性后的样品具有良好的亲水性, 反应72 h后, 其前进角由接枝前的130.45°下降到29.80°.     

Synthesis of miktoarm star amphiphilic block copolymers via combination of NMRP and ATRP and investigation on self‐assembly behaviors

The novel trifunctional initiator, 1‐(4‐methyleneoxy‐2,2,6,6‐tetramethylpip‐eridinoxyl)‐3,5‐bi(bromomethyl)‐2,4,6‐trimethylbenzene (TEMPO‐2Br), was successfully synthesized and used to prepare the miktoarm star amphiphilic poly(styrene)‐(poly(N‐isopropylacrylamide))₂ (PS(PNIPAAM)₂) via combination of atom transfer radical polymerization (ATRP) and nitroxide‐mediated radical polymerization (NMRP) techniques. Furthermore, the star amphiphilic block copolymer, poly (styrene)‐(poly(N‐isopropylacrylamide‐b‐4‐vinylpyridine))₂ (PS(PNIPAAM‐b‐P4VP)₂), was also prepared using PS(PNIPAAM)₂ as the macroinitiator and 4‐vinylpyridine as the second monomer by ATRP method. The obtained polymers were well‐defined with narrow molecular weight distributions (M_w/M_n ≤ 1.29). Meanwhile, the self‐assembly behaviors of the miktoarm amphiphilic block copolymers, PS(PNIPAAM)₂ and PS(PNIPAAM‐b‐P4VP)₂, were also investigated. Interestingly, the aggregate morphology changed from sphere‐shaped micelles (4.7 < pH < 3.0) to a mixture of spheres and rods (1.0 < pH < 3.0), and rod‐shaped nanorods formed when pH value was below 1.0. The LCST of PS(PNIPAAM)₂ (pH = 7) was about 31 °C and the LCST of PS(PNIPAAM‐b‐P4VP)₂ was about 35 °C (pH = 3). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6304–6315, 2009     

Influence of fluorinated substituent and terminal length on phase behavior of mesogen‐jacketed liquid crystalline polymers with a biphenyl mesogen

A series of mesogen‐jacketed liquid crystalline polymers, poly{2,2,3,3,4,4,4‐heptafluorobutyl 4′‐hydroxy‐2‐vinylbiphenyl‐4‐carboxylate} (PF3Cm, where m is the number of carbon atoms in the alkoxy groups, and m = 1, 4, 6, and 8), the side chain of which contains a biphenyl core with a fluorocarbon substituent at one end and an alkoxy unit of varying length on the other end, were designed and successfully synthesized via atom transfer radical polymerization. For comparison, poly{butyl 4′‐hydroxy‐2‐vinylbiphenyl‐4‐carboxylate} (PC4Cm), similar to PF3Cm but with a butyl group instead of the fluorocarbon substituent, was also prepared. Differential scanning calorimetric results reveal that the glass transition temperatures (T_gs) of the two series of polymers decrease as m increases and T_gs of the fluorocarbon‐substituted polymers are higher than those of the corresponding butyl‐substituted polymers. Wide‐angle X‐ray diffraction measurements show that the mesophase structures of these polymers are dependent on the number of the carbon atoms in the fluorocarbon substituent and the property of the other terminal substituent. Polymers with fluorocarbon substituents enter into columnar nematic phases when m ≥ 4, whereas the polymer PF3C1 exhibits no liquid crystallinity. For polymers with butyl substituents, columnar nematic phases form when the number of carbon atoms at both ends of the side chain is not equal at high temperatures and disappear after the polymers are cooled to ambient temperature. However, when the polymer has the same number of carbon atoms at both ends of the side chain, a hexagonal columnar phase develops, and this phase remains after the polymer is cooled. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

酶促聚合和原子转移自由基聚合“一锅法”合成嵌段聚合物及其性能表征

用酶促聚合和原子转移自由基聚合相结合的"一锅法"合成了聚甲基丙烯酸正丁酯嵌段聚10-羟基癸酸[PBMA-b-P(10-HD)],通过核磁共振(1H NMR)、傅里叶红外光谱(FTIR)和凝胶渗透色谱(GPC)对其结构以及分子量与其分子量分布进行了表征,并通过动态光散射仪(DLS)和原子力显微镜(AFM)对聚合物在水溶液中的性质进行了研究.所得嵌段聚合物纳米粒子呈球形结构,平均直径为135 nm左右.     

Preparation of gradient copolymers via ATRP in miniemulsion. II. Forced gradient

A series of forced gradient copolymers with different controlled distribution of monomer units along the copolymer backbone were successfully prepared by atom transfer radical polymerization in miniemulsion. The newly developed initiation technique, known as activators generated by electron transfer, was beneficial for forced gradient copolymers preparation because all polymer chains were initiated within the miniemulsion droplets and the miniemulsion remained stable throughout the entire polymerization. Various monomer pairs with different reactivity ratios were examined in this study, including n‐butyl acrylate/t‐butyl acrylate, n‐butyl methacrylate/methyl methacrylate, and n‐butyl acrylate/styrene. In each case, the added monomer diffused across the aqueous suspending medium and gradient copolymers with different forced distributions of comonomer units along the polymer backbone were obtained. The shape of the gradient along the backbone of the copolymers was influenced by the molar ratio of the monomers, the reactivity ratio of the comonomers as well as the feeding rate. The shape of the gradient was also affected by the relative hydrophobicities of the comonomers. Copolymerizations exhibited good control for all feeding rates and comonomer feeding ratios, as evidenced by narrow molecular weight distribution (M_w/M_n = 1.20–1.40) and molecular weight increasing smoothly with polymer yield, indicating high initiation efficiency. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1413–1423, 2007     

原子转移自由基聚合在智能型水凝胶制备中的应用

分别对原子转移自由基聚合和智能型水凝胶两者进行了综述,分析总结了利用原子转移自由基聚合制备智能型水凝胶方面的应用情况,并对其前景作了一定的展望.     

Preparation of intermediary layer crosslinked micelles from a photocrosslinkable amphiphilic ABC triblock copolymer

To prepare intermediary layer crosslinked micelles, a photocrosslinkable amphiphilic ABC triblock copolymer, poly(ethylene glycol)-b-poly(2-cinnamoyloxyethyl methacrylate)-b-poly(methyl methacrylate) (PEG-PCEMA-PMMA), was synthesized and its micellar characteristics were investigated. The triblock copolymer of PEG-b-poly(2-hydroxyethyl methacrylate)-b-PMMA (PEG-PHEMA-PMMA) (M_n = 9800 g/mol, M_w/M_n = 1.33) was first polymerized by activators generated by electron transfer (AGET) atom transfer radical polymerization (ATRP) using a PEG macroinitiator in a mixed solvent of anisole/2-isopropanol (3/1 v/v). The middle block of the copolymer was then functionalized with cinnamoyl chloride. The degrees of polymerization of the PEG, PHEMA, and PMMA blocks were 113, 18 and 21, respectively. The critical micelle concentration (CMC) of the PEG-PCEMA-PMMA was 0.011 mg/mL. The PEG-PCEMA-PMMA micelles were spherically shaped with an average diameter of 43 nm. The intermediary layer of the PEG-PCEMA-PMMA micelles was crosslinked by UV irradiation. Not all of the cinnamate groups underwent photocrosslinking probably due to a lack of other cinnamate groups in their immediate vicinity. However, the degree of photocrosslinking of the intermediary layer of the PEG-PCEMA-PMMA micelles was sufficient to give excellent colloidal stability, even in different external environments.     

基于ATRP技术的多嵌段共聚物研究进展

原子转移自由基聚合(ATRP)技术是合成结构规整性聚合物的有效途径。综述了近十年来采用ATRP技术合成多嵌段共聚物的研究进展。从引发剂、共聚单体和反应条件等方面讨论了ABA型、ABC型和ABCBA型等类型多嵌段共聚物的合成、性质与潜在应用。对原子转移自由基聚合技术在合成功能性多嵌段共聚物中的应用前景进行了展望。