Preparation of hyperbranched polymers by atom transfer radical polymerization

A cheap acrylic AB* monomer, 2‐(2‐chloroacetyloxy)‐isopropyl acrylate (CAIPA), was prepared from 2‐hydroxyisopropyl acrylate with chloroacetyl chloride in the presence of triethylamine. The self‐condensing vinyl polymerization by atom transfer radical polymerization (ATRP), a “living”/controlled radical polymerization, has yielded hyperbranched polymers. All the polymerization products were characterized by proton nuclear magnetic resonance spectroscopy (¹H NMR). CAIPA exhibited distinctive polymerization behavior that is similar to a classical step‐growth polymerization in the relationship of molecular weight to polymerization time, especially during the initial stage of the polymerization. However, a significant amount of monomer remained present throughout the polymerization, which is consistent with typical chain polymerization. Also, if a much longer polymerization time was used, the polymer became gel. As a result of the unequal reactivity of group A* and B*, the polymerization is different from an ideal self‐condensing vinyl polymerization: the branch structures of polymers prepared depend dramatically on the ratio of 2,2'‐bipyridyl to CAIPA. Hyperbranched polymers exhibit improved solubility in organic solvent, however, they have lower thermal stability than their linear analogs. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2114–2123, 2002     

Preparation and characterization of hyperbranched polyacrylate copolymers by self‐condensing vinyl copolymerization (SCVCP)

A series of hyperbranched polyacrylate copolymers have been synthesized by self‐condensing vinyl copolymerization (SCVCP) of 2‐(2‐bromopropionyloxy)‐ethyl acrylate (BPEA) and methyl acrylate (MA) in the presence of CuBr and bipyridine. The structures and properties of the polymers obtained are characterized by NMR and SEC/RALLS/DV/RI measurements. The effects of reaction conditions on molecular weight (MW), molecular weight distribution (MWD) and degree of branching (DB) are investigated. © 2002 Society of Chemical Industry     

Preparation of branched polyacrylonitrile through self‐condensing vinyl copolymerization

Branched polyacrylonitrile (PAN) was prepared through a self‐condensing vinyl copolymerization of acrylonitrile and 2‐(2‐bromopropionyloxy)ethyl acrylate (BPEA). The branched architecture of the product was confirmed by NMR spectra and the average degree of branching (DB ) was estimated. Through a comparison of the intrinsic viscosity of the product with that of its linear analogue, the contraction factor g′ was calculated. It was found that the viscosity of the branched PAN was obviously lower that that of linear PAN. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis and characterization of hyperbranched cationic polyelectrolytes via aqueous self‐condensing atom transfer radical polymerization

The hyperbranched cationic polyelectrolytes (PDMEAB) were directly prepared via the CuBr/ligand‐catalyzed (ligand = 2,2′‐bipyridine or pentamethyldiethylenetriamine) aqueous self‐condensing atom transfer radical polymerization (SCATRP) of a novel inimer, N,N‐dimethyl‐N‐(2‐methacryloyloxy)ethyl‐N‐(2‐bromoisobutyryloxy)ethyl ammonium bromide (DMEAB). Elemental analysis and nuclear magnetic resonance (NMR) spectroscopy confirmed the structure of DMEAB. The hyperbranched architecture and number‐average degree of polymerization (DP_n) of the PDMEAB was studied by ¹H‐ and ¹³C‐NMR. The kinetic results suggested that the DP_n of the hyperbranched PDMEAB grew gradually in the initial stage and exponentially in the later stage. The differential scanning calorimetry (DSC) showed that the glass transition temperature of the hyperbranched PDMEAB was much lower than that of the linear analogue. The solution rheometry showed that the aqueous PDMEAB solutions approximately underwent a Newtonian behavior and their shear viscosity maintained almost constant upon the addition of NaCl because of the spherical conformations of the hyperbranched cationic polyelectrolytes. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

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.     

Studies on the preparation of branched polymers from styrene and divinylbenzene

The self‐condensing vinyl polymerization of styrene and an inimer formed in situ by atom transfer radical addition from divinylbenzene and 2‐bromoisobutyl‐tert‐butyrate using atom transfer radical polymerization technique was studied. To study the polymerization mechanism and achieve high molecular weight polymer in a high polymer yield, the polymerization was carried out in bulk at 80°C. Proton nuclear magnetic resonance (¹H‐NMR) spectroscopy and gel permeation chromatography (GPC) coupled with multiangle laser light scattering (MALLS) were used to monitor the polymerization process and characterize the solid polymers. It is proved that the polymerization shows a “living” polymerization behavior and the crosslinking reaction has been restrained effectively due to the introduction of styrene. Polymers with high molecular weight (M_w.MALLS > 10⁵) can be prepared in high yield (near 80%). Comparison of the apparent molecular weights measured by GPC with the absolute values measured by MALLS indicates the existence of branched structures in the prepared polymers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

原位生成自引发单体合成支化共聚物

以α-溴代异丁酸叔丁酯为引发剂,二乙烯苯为支化单体,苯乙烯为共聚单体,经原子转移自由基聚合原位生成自引发单体合成支化共聚物。用核磁共振法、凝胶渗透色谱法、三角激光散射法分别对聚合过程和聚合物进行了表征。结果表明：由于苯乙烯的引入,反应体系的交联得到了很好的控制,所得聚合物为支化结构。     

Hyperbranched polyacrylates prepared by self‐condensing vinyl copolymerization in the presence of a tetrafunctional initiator

Hyperbranched copolymers were synthesized by self‐condensing vinyl copolymerization (SCVCP) of 2‐[(2‐bromopropionyl)oxy]ethyl acrylate (BPEA) and methyl acrylate (MA) in the presence of a tetrafunctional initiator, 6,6‐bis[5‐(α‐bromoisobutyryloxy)‐2‐oxapentyl]‐4,8‐dioxaundecane‐yl‐1,11 dibromoisobutyrate (THABI). The structures of the polymers obtained were characterized by NMR and size exclusion chromatography/right‐angle laser‐light scattering/differential viscometry/differential refractometry. Molecular weight, molecular weight distribution and degree of branching were influenced by conversion and initial feed molar ratio of BPEA, MA and THABI. The addition of THABI can narrow the polydispersity of the hyperbranched copolymers obtained. The results are consistent with our previous simulation work. © 2003 Society of Chemical Industry     

Solution properties of hyperbranched polymers and synthetic application for amphiphilic star‐hyperbranched copolymers by grafting from hyperbranched macroinitiator

Hyperbranched polystyrenes (PS) were prepared by living radical photopolymerization of N,N‐diethyldithiocarbamoylmethylstyrene (DTCS) as an inimer under UV irradiation. Branched PS with an average chain length between branching points of four styrene units was also prepared by living radical copolymerization of DTCS with styrene. The ratio of radius of gyration to hydrodynamic radius R_G/R_H for these hyperbranched polymers was in the range 0.82–0.89 in toluene. The translational diffusion coefficient D(C) showed a constant value in the range of 0–14 × 10^?3 g ml^?1 in toluene. It was found from these dilute solution properties that hyperbranched PSs formed a unimolecular structure even in a good solvent because of their compact nature. These hyperbranched PSs exhibited large amounts of photofunctional carbamate (DC) groups on their outside surfaces. Subsequently, we derived amphiphilic star‐hyperbranched copolymers by grafting from hyperbranched macroinitiator with 1‐vinyl‐2‐pyrrolidinone. These star‐hyperbranched copolymers were soluble in water and methanol. © 2001 Society of Chemical Industry     

ATRP of acrylonitrile catalyzed by FeCl2/succinic acid under microwave irradiation

A single‐pot atom‐transfer radical polymerization (ATRP) under microwave irradiation was first used to successfully synthesize polyacrylonitrile. This was achieved by using FeCl₂/succinic acid as the catalyst and 2‐chloropropionitrile as the initiator. Using the same experimental conditions, the apparent rate constant under microwave irradiation was found to be higher than that under conventional heating. The FeCl₂/succinic acid ratio of 1 : 2 not only gives the best control of molecular weight and its distribution but also provides rather rapid reaction rate. When FeCl₂ was replaced with CuCl, ATRP of AN does not show an obvious living characteristics. To demonstrate the active nature of the polymer chain end, the polymers were used as macroinitiators to proceed the chain‐extension polymerization. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1598–1601, 2006     

Formation of a soluble hyperbranched polymer via initiator–fragment incorporation radical copolymerization of divinyl adipate and isobutyl vinyl ether

The copolymerization of divinyl adipate (DVA) with isobutyl vinyl ether (IBVE) was conducted at 70 and 80 °C in benzene using azobisisobutyronitrile (AIBN), at a concentration as high as 0.50 mol l^?1 as the initiator, where the concentrations of DVA and IBVE were 0.40 and 0.60 mol l^?1, respectively. The copolymerization proceeded homogeneously, without any gelation, to yield soluble copolymers in spite of the high molar ratio of DVA as an excellent cross‐linker for IBVE. The copolymer yield increased with time, and the number‐average molecular weight (M_n = 0.9–2.4 × 10⁴ g mol^?1) from gel permeation chromatography (GPC) and molecular weight distribution (M_w/M_n = 1.5–7.6) of the resulting copolymer increased with copolymer yield. The cyanopropyl group, as a fragment of AIBN, was incorporated as a main constituent in the copolymer, the fraction of which increased from ca 10 to ca 20 % with copolymer yield, hence indicating that the copolymerization is an initiator–fragment incorporation radical polymerization. The copolymers also contained IBVE units (10–30 %) and DVA units with intact double bond (8–36 %) and without double bond (45 %). The intrinsic viscosity of the copolymer was very low (0.1 dl g^?1) at 30 °C in tetrahydrofuran. The results from GPC–multi‐angle laser light scattering (MALLS), transmission electron microscopy (TEM) and MALLS revealed that individual copolymer molecules were formed as hyperbranched nanoparticles. Copyright © 2004 Society of Chemical Industry     

Synthesis of multi‐arm star polystyrene with hyperbranched polyester initiators by atom transfer radical polymerization

Multi‐arm star polystyrenes with hyperbranched polyester (HP3) core were prepared by atom transfer radical polymerization (ATRP). The structures of the polymers were investigated with FTIR and ¹H NMR. GPC results showed that the resultant polymers had relatively broad polydispersity indices that arouse from the macromolecular initiator (HP3‐Br). The thermal properties were studied using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). DSC analysis indicated that polystyrene star polymers had only the glass transition temperatures (T_g), which changes with the weight ratio of multi‐functional macroinitiator‐to‐monomer. In addition, these star polymers could form the spherical micelles in the selected solvent (THF/n‐hexane). © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 728–733, 2006     

An iron‐based reverse ATRP process for the living radical polymerization of acrylonitrile

A hexa‐substituted ethane thermal iniferter, diethyl‐2,3‐dicyano‐2,3‐di(p‐tolyl) succinate (DCDTS), was firstly used as the initiator in the reverse atom transfer radical polymerization (RATRP) of acrylonitrile. FeCl₃ coordinated by isophthalic acid (IA) was used as the catalyst in this system. The polymerization in N,N‐dimethylformamide not only shows the best control of molecular weight and its distribution but also provides rather rapid reaction rate with the ratio of [AN] : [DCDTS] : [FeCl₃] : [IA] at 500 : 1 : 2 : 4. The polymers obtained were end‐functionalized by chlorine atom, and they were used as macroinitiators to proceed the chain extension polymerization in the presence of FeCl₂/IA catalyst system via a conventional ATRP process and polyacrylonitrile obtained was with M_n = 39,260, PDI = 1.25. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Synthesis of mid-dicarboxy polystyrene by ATRP and formation of ionic-bonded supramolecules

Dimethyl 4,6-bis(bromomethyl) isophthalate was synthesized by bromomethylation, oxidation, esterification and bromination of 1,3-dimethylbenzene. This was used to initiate the atom transfer radical polymerization of styrene successfully. Results showed that the process had some of the good characteristics of controlled/living free radical polymerization. The molecular weight of the obtained polymer increased linearly with monomer conversion, its molecular weight distribution was very narrow, and a linear relationship between ln([M]₀/[M]) and polymerization time was found. A well-defined novel structural polystyrene containing two ester groups in the mid-main chain was prepared with controlled molecular weight and narrow polydispersity. The structure of the polymer was confirmed by ¹H-NMR spectra. After being hydrolyzed, dicarboxy polystyrene was obtained and used to form ionic-bonded supramolecules with 1-dodecanamine as a model of the star-shaped supramolecules. The supramolecules formed were characterized by Fourier transform infrared (FTIR) spectrum. Translated from Acta Polymerica Sinica, 2006, (4): 597–602 [译自: 高分子学报]     

基于ATRP/CuAAC反应的降冰片烯类大分子单体的制备

利用原子转移自由基聚合合成了聚丙烯酸叔丁酯聚苯乙烯嵌段共聚物,通过取代反应在聚合物末端修饰叠氮基团,随后采用铜催化的叠氮-炔基环加成反应将含有炔基的顺-5-降冰片烯-外-2,3-二酸酐衍生物与嵌段共聚物偶联,得到大分子单体,最后通过大分子单体的开环易位聚合,制备了具有"Y"形的聚合物。通过核磁共振波谱仪、凝胶渗透色谱仪、原子力显微镜等研究了聚合物的结构与形貌。结果表明:通过活性可控聚合技术可以得到设计良好的具有复杂拓扑结构的聚合物。     

超支化环氧树脂的研究进展及应用前景

综述了各类超支化环氧树脂的合成工艺,主要包括聚酯型、聚醚型、聚酯聚醚型和聚烷烃超支化环氧树脂.超支化环氧树脂的合成工艺主要有缩水甘油直接法、环氧氯丙烷间接法、原子基团转移聚合法、双键加成法.对每种超支化环氧树脂的合成工艺、产品特征进行分析.提出了超支化环氧树脂在热固性材料、胶粘剂和作为无溶剂树脂等领域的应用前景.     

Chemo‐enzymatic synthesis of poly(2,2,2‐trichloroethyl 10‐hydroxydecanate)‐block‐polystyrene combining enzymatic self‐condensation polymerization and ATRP

Enzymatic polymerization in a non‐natural environment is of interest as an environmentally friendly methodology as an alternative to the use of conventional chemical organometallic catalysts. Chemo‐enzymatic synthesis of the AB‐type diblock copolymer poly(2,2,2‐trichloroethyl 10‐hydroxydecanate)‐block‐polystyrene (PHD‐b‐PSt) was carried out by combining enzymatic self‐condensation polymerization (eSCP) and atom‐transfer radical polymerization (ATRP). Biocatalyst Novozyme 435 was successful in catalyzing the eSCP of a novel ω‐hydroxyester, i.e. 2,2,2‐trichloroethyl 10‐hydroxydecanate. The resulting ? CCl₃‐terminated PHD initiated the ATRP of styrene, a ‘living’/controlled radical polymerization. The analysis of the hydrolysate from the copolymer proved the presence of a block copolymer structure. In addition, the well‐defined diblock copolymer PHD‐b‐PSt self‐assembled into nanoscale micelles in aqueous solution. The chemo‐enzymatic synthesis of diblock copolymer PHD‐b‐PSt was achieved by the combination of eSCP and ATRP. The structures and composition of the block copolymer were characterized by means of NMR, infrared and gel permeation chromatography measurements. Differential scanning calorimetry analysis showed that a microphase‐separation structure was formed in the copolymer, which was caused by the crystallization of the PHD segments. As investigated with atomic force microscopy and dynamic light scattering, these micelles had a mean diameter and a spherical shape. To our knowledge, this is the first example of a chemo‐enzymatic synthesis based on eSCP and ATRP. Copyright © 2007 Society of Chemical Industry     

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