New architectures of poly(ethylene glycol) and poly(methylthiirane) in block copolymers

Two synthetic ways were experimented to prepare new architectures of block copolymers made of poly(ethylene glycol) (PEG) and poly(methylthiirane). The coupling of both blocks conveniently end-capped as well as anionic polymerization of methylthiirane initiated by PEG-thiols gave readily the copolymers. Their characterization by ¹H NMR, SEC and IR confirmed the expected structures.     

Synthesis of oligo(ethylene glycol) methacrylate polymer brushes

Here we report a study into controlling the polymerization of mono-hydroxy and mono-methoxy terminated oligo(ethylene glycol) methacrylates (HOEGMA and MeOEGMA, respectively) from functionalised, planar surfaces via atom transfer radical polymerization (ATRP). The effects of initiator structure, initiator density, temperature, and monomer ratios have been investigated for these polymerizations. The polymer brushes grown in this way were found to convey protein resistance to the underlying inorganic substrates, prone to facile protein adsorption in their native state.     

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.     

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.     

AGET ATRP of methyl methacrylate with poly(ethylene glycol) (PEG) as solvent and TMEDA as both ligand and reducing agent

Activator generated by electron transfer atom transfer radical polymerization of methyl methacrylate (MMA) in inexpensive, non-toxic poly(ethylene glycol) (PEG), with air-stable Cu(II)X₂(X = Br, Cl) as the catalyst and N,N,N′,N′-tetramethylethylenediamine (TMEDA) as both ligand and reducing agent was investigated. The polymerizations in PEG proceeded in a well-controlled manner as evidenced by kinetic studies and chain extension results. The polydispersity of the polymer obtained was quite narrow, with a weight-average molecular weight/number-average molecular weight ratio of less than 1.2. Effects of the TMEDA content and the catalysts on polymerization were also investigated, respectively.     

Polycaprolactone–poly(ethylene glycol) block copolymer,I: synthesis and degradability in vitro

A new type of biodegradable polymer material, poly(caprolactone)–poly(ethylene glycol) block copolymer (PCL-b-PEG), was synthesized by means of direct copolycondensation of ε-caprolactone with poly(ethylene glycol) in the presence of a Ti(OBu)₄ catalyst. The degradability of the polycaprolactone was improved by introducing a PEG component into it. The degradation of PCL-b-PEG copolymer increase with a decreasing crystallinity of the copolymer, and can be controlled by adjusting the component ratio of the copolymer.     

Synthesis of hyperbranched-linear star block copolymers by atom transfer radical polymerization of styrene using hyperbranched poly(siloxysilane) (HBPS) macroinitiator

Hyperbranched-linear star block copolymers, hyperbranched poly(siloxysilane)-block-polystyrene (HBPS-b-PSt), were prepared by atom transfer radical polymerization (ATRP) of styrene in xylene, using bromoester-terminated HBPS (HBPS-Br (P3), M_n = 7500, M_w/M_n = 1.76) as a macroinitiator. The number-average molecular weights of the obtained polymers (M_n) were in the range of 21,800-60,000 and molecular weight distributions were unimodal throughout the reaction (M_w/M_n = 1.28-1.40). These polymers showed 5 wt.% decomposition temperature (T_d5) over 300 °C. The DSC thermograms of the resulting polymers indicated two glass transition temperatures (T_g). The T_g of HBPS segment shifted to higher value while the T_g of PSt segment shifted to lower value compared with those of the homopolymers. Preliminary physical characterization related to the solution viscosity of the resulting block copolymers is also reported.     

Segmented block copolymers of poly(ethylene glycol) and poly(ethylene terephthalate)

A new series of segmented copolymers were synthesized from poly(ethylene terephthalate) (PET) oligomers and poly(ethylene glycol) (PEG) by a two‐step solution polymerization reaction. PET oligomers were obtained by glycolysis depolymerization. Structural features were defined by infrared and nuclear magnetic resonance (NMR) spectroscopy. The copolymer composition was calculated via ¹H NMR spectroscopy. The content of soft PEG segments was higher than that of hard PET segments. A single glass‐transition temperature was detected for all the synthesized segmented copolymers. This observation was found to be independent of the initial PET‐to‐PEG molar ratio. The molar masses of the copolymers were determined by gel permeation chromatography (GPC). © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4448–4457, 2004     

Small-angle neutron scattering study on microstructure of poly(N-isopropylacrylamide)-block-poly(ethylene glycol) in water

By employing small-angle neutron scattering (SANS), we investigated the microstructures of, poly(N-isopropylacrylamide) (PNIPA)-block-poly(ethylene glycol) (PEG) (NE) in deuterated water D₂O, as related to macroscopic behaviors of fluidity, turbidity and synerisis. SANS revealed following results: (i) microphase separation occurs at around above 17 °C in a temperature range of transparent sol below 30 °C. In the microdomain appeared in the transparent sol state, both block chains of PNIPA and PEG are swollen by water; (ii) for the NE solution of polymer concentration W_p > 3.5% (w/v), corresponding to opaque gel above 30 °C, a percolated structure, i.e., network-like domain is formed by NE as a result of macrophase separation due to dehydration of the PNIPA chains. As the temperature increases toward 40 °C, the network domain is squeezed along a direction parallel to the NE interface, which leads to increase of the interfacial thickness given by swollen PEG chains and to the macroscopic synerisis behavior.     

Soft nanoparticles assembled from linear poly(ethylene glycol) and linear brush polydimethylsiloxane diblock copolymers

A series of novel amphiphilic diblock copolymers composed of hydrophilic linear poly(ethylene glycol) (PEG) and linear brush hydrophobic polydimethylsiloxane (PDMS) were synthesized. Three different molecular weights of monomethyl ether PEG were initially functionalized with 2‐bromoisobutyryl bromide to afford macroinitiators suitable for atom‐transfer radical polymerization. The macroinitiators were characterized by gel permeation chromatography, ¹H and ¹³C nuclear magnetic resonance spectroscopic analysis and matrix‐assisted laser desorption ionization time‐of‐flight mass spectroscopy. The three different molecular weight macroinitiators were then chain extended with monomethacryloxypropyl‐terminated PDMS and photoactive 2‐(methylacyloyloxy)ethyl anthracene‐9‐carboxylate in different molar ratios to afford a series of photoresponsive amphiphilic diblock copolymers with high conversions. Self‐assembly of these linear–linear brush diblock copolymers in N,N‐dimethylformamide afforded nanoparticles with hydrodynamic diameters (d_H) ranging from 41 to 268 nm, as determined by dynamic light scattering analysis. Crosslinking and stabilization of the nanoparticles was achieved via [4+4] photodimerization of the anthracene moieties upon exposure to UV radiation at 365 nm with the reverse reaction studied at a wavelength of 254 nm. Transmission electron microscopy revealed that the self‐assembled nanoparticles and their crosslinked derivatives had spherical morphologies. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1251–1262     

Straightforward synthesis of poly(lauryl acrylate)-b-poly(stearyl acrylate) diblock copolymers by ATRP

Lauryl (LA) and stearyl (SA) acrylates were successfully polymerized by atom transfer radical polymerization (ATRP), leading to well defined homopolymers and diblock copolymers (PDI < 1.2). Interestingly, the polymerization was very well controlled using N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA), a ligand which had initially been reported to be unadvisable for the polymerization of such monomers. Both kinetic studies and chain extension reactions supported our conclusions. A PLA₆₅-b-PSA₄₇ diblock copolymer was characterized by differential scanning calorimetry and dynamic thermo-mechanical analysis, revealing that both blocks exhibit side-chain crystallinity and phase segregate in the crystalline state. The diblock behaves as a brittle rigid polymer when both blocks are crystalline, as a ductile material after the melting of the PLA phase and becomes a viscous liquid when both blocks are molten. This work could be extended to the preparation of PSA-b-PLA-b-PSA bio-issued thermoplastic elastomers.     

Synthesis and characterization of poly(phenylene oxide) graft copolymers by atom transfer radical polymerizations

A series of comb-like poly(phenylene oxide)s (PPO) graft copolymers with controlled grafting density and length of grafts were synthesized by atom transfer radical polymerization (ATRP). The α-bromo-poly(2,6-dimethyl-1,4-phenylene oxide)s (BPPO) were used as macroinitiators to polymerize vinyl monomers and the graft copolymers carrying polystyrene (PS), poly(p-acetoxystyrene) (PAS), and poly(methyl methacrylate) (PMMA) as side chains were synthesized and characterized by NMR, FTIR, GPC, DSC and TGA. The composition-dependent glass-transition temperatures (T_g) of PPO-g-PS exhibited good correlation with theoretical curve in Couchman equations except for the cases of low PS content (<40 mol%) copolymers in which a positive deviation was observed due to enhanced molecular interactions. The increase in monomer/initiator ratio led to the increase of degree of polymerization and the decrease of polydispersity. Despite the immiscibility nature between PPO and PMMA, the PPO-g-PMMA exhibited enhanced compatibilization as apparent single T_g in a wide temperature window throughout various compositions revealing an efficient segmental mixing on a molecular scale due to grafting structure.     

Atom transfer radical polymerization of styrene from different poly(ethylene terephthalate) surfaces: Films, fibers and fabrics

Poly(ethylene terephthalate) (PET) is a semi-crystalline thermoplastic polyester used in many fields. For a variety of applications, however, it is necessary to impart desired properties by introducing specific functional groups on the surface. A simple method for growing polymer brushes by atom transfer radical polymerization (ATRP) on PET films, fibers and fabrics was devised. The different PET surfaces were first reacted with 1,2-diaminoethane by aminolysis reaction to incorporate primary amino and alcohol functions on the surface. Then, in a second step, ATRP initiator was grafted by reaction with bromoisobutyryl bromide. The efficiency of these reactions was confirmed by using colorimetric titration and X-ray photoelectron spectroscopy (XPS). Surface-initiated ATRP was performed in bulk using styrene monomer with CuBr/PMDETA catalytic system in the presence of a sacrificial initiator (ethyl 2-bromoisobutyrate). Good control of the polymerization was obtained as attested by comparison of polystyrene molar masses obtained in solution from sacrificial initiator with those obtained from the surface after cleavage. Wetting properties were found to vary systematically depending to the type of functionalization and grafting. Evolution of surface morphology according to reaction steps was investigated using atomic force microscopy (AFM).     

Synthesis and MALDI-TOF-MS of PS-PMA and PMA-PS block copolymers

The synthesis of well-defined block copolymers from styrene and methyl acrylate via ATRP is discussed in this contribution. Kinetic studies on these block copolymerizations as well as characterization studies were performed to investigate the monomer composition in the respective PS and PMA blocks. MALDI-TOF-MS was performed to clarify the exact number of repeating units of each block and the total number of units in the block copolymer. Block copolymers up to 22 kDa could be analyzed by MALDI-TOF-MS, whereby polymers with PMA as first block showed a large second distribution corresponding to PMA homopolymers. However, SEC demonstrated that only a small amount of homopolymer was present indicating that care needs to be taken with interpreting MALDI-TOF-MS data, which is a qualitative rather than a quantitative technique.     

原子转移自由基聚合(ATRP)制备高密度端羟基聚氧乙烯梳状嵌段聚合物

聚氧乙烯[Poly(ethylene glycol),PEG]是一种稳定、无毒且具有良好的生物惰性和非免疫性、非抗原性的水溶性聚合物,在生物医学和生物技术领域具有广泛的应用背景和重要的研究意义,大量研究表明,多臂的PEG由于其枝状结构具有比线型结构更好的性能,然而,通常多臂,PEG采用Corefirst阴离子开环聚合环氧乙烷的方法,这种方法对聚合条件及设备等要求较高,限制了多臂的PEG的应用。     

Thermosensitive behavior of poly(ethylene glycol)/poly(2‐(N,N‐dimethylamino)ethyl methacrylate) double hydrophilic block copolymers

The poly(ethylene glycol)/poly(2‐(N,N‐dimethylamino)ethyl methacrylate) (PEG/PDMAEMA) double hydrophilic block copolymers were synthesized by atom transfer radical polymerization using mPEG‐Br or Br‐PEG‐Br as macroinitiators. The narrow molecular weight distribution of PEG/PDMAEMA block copolymers was identified by gel permeation chromatography results. The thermosensitivity of PEG/PDMAEMA block copolymers in aqueous solution was revealed to depend significantly on pH, ionic strength, chain structure, and concentration of the block copolymers. By optimizing these factors, the cloud point temperature of PEG/PDMAEMA block copolymers can be limited within body temperature range (30–37 °C), which suggests that PEG/PDMAEMA block copolymers could be a good candidate for drug delivery systems. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 503–508, 2010     

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.     

Crystallization behavior and biodegradation of poly(3-hydroxybutyrate) and poly(ethylene glycol) multiblock copolymers

Block copolymerization by using isocyanates is an effective method for incorporating PHB and PEG because it can prepare copolymers with good properties, such as toughness, strength, and so on. In this study, we adopted soil suspension system to estimate the biodegradability of a series of PHB/PEG multiblock copolymers with different compositions and block lengths. In the degradation process, the changes in weight loss, molecular weight, and tensile strength were periodically measured to determine the biodegradability, and the surface morphology was also observed by SEM. In contrast to pure PHB, the weight loss of the copolymer was relatively lower. On the other hand, the tensile strength and molecular weight experienced apparent decrease, and for BHG1000-3-1, they reached 46.7% and 77.7% of the initial value, respectively. SEM observation showed that the surface was covered with numerous erosion pits. All these indicate that the degradation indeed took place and long-chain molecules have been hydrolyzed into shorter ones. The crystallization behavior was also investigated by DSC and WAXD. The results showed that both the segments, PEG and PHB, can form crystalline phases at lower PHB contents ranging from 29% to 44%, and when PHB component was more than 60%, only PHB phase can crystallize.     

Novel ABC2-type liquid-crystalline block copolymers with azobenzene moieties prepared by atom transfer radical polymerization

A series of novel ABC₂-type liquid-crystalline block copolymers with azobenzene moieties in the side chains were prepared by combination of atom transfer radical polymerization (ATRP) and the chemical modification reaction. First, the bromine-terminated diblock copolymer poly(ethylene oxide) monomethyl ether-block-polystyrene (MPEO-PS-Br) was prepared by ATRP of styrene initiated with macroinitiator MPEO-Br, which was obtained from the esterification of MPEO and 2-bromoisobutyryl bromide. Then, the bromo end groups of the resulting MPEO-PS-Br were derivatized into twice as many bromoisobutyrates by the chain end modification reaction to obtain ω,ω′-bis(bromo)-PS-MPEO (MPEO-PS-Br₂). The azobenzene-containing blocks of poly[6-(4-methoxy-azobenzene-4′-oxy) hexyl methacrylate] (PMMAZO) with different molecular weights were introduced into the derivative diblock copolymer by a second ATRP to synthesize the novel ABC₂-type liquid-crystalline block copolymers poly(ethylene oxide) monomethyl ether-block-polystyrene-block-{poly[6-(4-methoxy-azobenzene-4′-oxy) hexyl methacrylate]}₂ [MPEO-PS-(PMMAZO)₂].