New Strategy Targeting Well‐Defined Polymethylene‐block‐Polystyrene Copolymers: The Combination of Living Polymerization of Ylides and Atom Transfer Radical Polymerization

Well‐defined polymethylene‐block‐polystyrene (PM‐b‐PS) diblock copolymers were synthesized via a combination of living polymerization of ylides and atom transfer radical polymerization (ATRP) of styrene. A series of hydroxyl‐terminated polymethylenes (PM‐OHs) with different molecular weight and narrow molecular weight distribution were prepared using living polymerization of ylides following efficient oxidation in a quantitive functionality. Then, the macroinitiators (PM‐MIs ( = 1 900–15 000; PDI = 1.12–1.23)) transformed from PM‐OHs in ≈ 100% conversion initiated ATRPs of styrene to construct PM‐b‐PS copolymers. The GPC traces indicated the successful extension of PS segment ( of PM‐b‐PS = 5 000–41 800; PDI = 1.08–1.23). Such copolymers were characterized by ¹H NMR and DSC.

     

刚柔嵌段共轭聚合物自组装体系*

刚柔嵌段共轭聚合物的自组装是超分子化学研究的热点之一。本文综述了近年来刚柔嵌段共轭聚合物自组装体系研究进展。根据共轭刚性段的不同分类进行阐述,综述了聚芴,二（苯乙烯）-蒽,聚对苯撑,聚对苯乙烯撑,聚对苯撑乙炔,聚（2,5-苯甲酮）,聚噻吩,聚苯基喹啉等作为刚性链段的刚柔嵌段共轭聚合物自组装体系,介绍了刚柔嵌段共轭聚合物的合成和光物理性质;重点评述了刚柔嵌段共轭聚合物在不同溶剂、浓度、温度等条件下自组装形成一维、二维以及三维的周期性微结构,且具有方便的可控性。概括了刚柔嵌段共轭聚合物自组装体系广阔的应用前景,尤其在光电器件领域有着潜在的应用价值。最后展望了刚柔嵌段共轭聚合物自组装体系研究和发展的方向。     

Synthesis and Characterization of Helix‐Coil Diblock Copolymers with Controlled Supramolecular Architectures in Aqueous Solution

Summary: A series of helix‐coil diblock copolymers based on poly(ethylene oxide) and optically active helical poly{(+)‐2,5‐bis[4′‐((S)‐2‐methylbutoxy)phenyl]styrene} (PMBPS) were synthesized via atom transfer radical polymerization (ATRP). The synthetic methodology permitted straightforward preparation of the diblock copolymers with relatively low polydispersities and a broad range of compositions and molecular weights. Depending on the composing block length and the initial concentration, the copolymers self‐assembled into different supramolecular structures in aqueous solution, including spherical micelles, vesicles, multilamellar vesicles, large compound vesicles, and tubules.

Schematic representation of the synthesis of PEO‐b‐PMBPS block copolymers and their aggregation in aqueous solution.     

ATRP和点击化学结合法制备PDMAAm—PDMS—PDMAAm嵌段聚合物

采用原子转移自由基聚合（ATRP）法制得了端基分别为烯丙基和溴原子的聚二甲基丙烯酰胺（PDMAAm）,经叠氮基亲核取代后与端炔基聚二甲基硅氧烷进行点击反应,得到两亲三嵌段聚合物。利用^1HNMR、FTIR、GPC等测试方法对聚合物的结构进行了表征。结果表明：采用ATRP法合成的PDMAAm均聚物分子量分布较窄,通过点击化学法将热力学不相容的亲水性PDMAAm链段及疏水性聚二甲基硅氧烷（PDMS）链段制备PDMAAmPDMS—PDMAAm嵌段聚合物,是一种高效易行的方法。     

Synthesis of Block Copolymers Modified with Phosphonate Ester Groups Using Nitroxide‐Mediated Radical Polymerization

Summary: Phosphonate groups were introduced into block copolymers of styrene derivatives either as single end‐groups or as small blocks using nitroxide‐mediated radical polymerization. In order to combine the hydrophobic and hydrophilic segments, block copolymers with N,N‐dimethyl acrylamide were synthesized. After hydrolysis to phosphonic acid groups, adsorption of the polymer onto metal oxides was possible.

Conversion of the phosphonate groups by transesterification with trimethylbromosilane (TMBS), followed by hydrolysis of the silylester group.     

Synthesis of Block Copolymers by Combination of Atom Transfer Radical Polymerization and Visible Light‐Induced Free Radical Promoted Cationic Polymerization

A new synthetic approach for the preparation of block copolymers by mechanistic transformation from atom transfer radical polymerization (ATRP) to visible light‐induced free radical promoted cationic polymerization is described. A series of halide end‐functionalized polystyrenes with different molecular weights synthesized by ATRP were utilized as macro‐coinitiators in dimanganese decacarbonyl [Mn₂(CO)₁₀] mediated free radical promoted cationic photopolymerization of cyclohexene oxide or isobutyl vinyl ether. Precursor polymers and corresponding block copolymers were characterized by spectral, chromatographic, and thermal analyses.     

Novel Functional Mesoporous Materials Obtained from Nanostructured Diblock Copolymers

Summary: Novel carboxy (COOH)-functionalized mesoporous polystyrene membranes were prepared from polystyrene-block-poly(D,L-lactide) (PS-b-PLA) diblock copolymers through the selective degradation of the PLA block. The combination of atom transfer radical polymerization (ATRP) and ring-opening polymerization (ROP) techniques enabled the synthesis of nanostructured diblock copolymers possessing carboxylic acid functionality at the junction between both blocks. Such copolymers were subjected to shear flow through the use of a channel die to align their nanodomains. Under mild alkaline conditions, the quantitative hydrolysis of the polyester nanodomains afforded mesoporous materials with COOH-coated pore walls. The PS-b-PLA precursors as well as the resulting porous systems were carefully analyzed by size exclusion chromatography (SEC), ¹H NMR, scanning electron microscopy (SEM), and two-dimensional small-angle X-ray scattering (2-D SAXS). Moreover, the specific surface area and pore size distribution were determined by nitrogen sorption porosimetry.     

Block Copolymer PEO‐b‐PHPMA Synthesis Using Controlled Radical Polymerization on a Chip

Summary: Block copolymers of poly(ethylene oxide‐block‐2‐hydroxypropyl methacrylate) (PEO‐b‐PHPMA) with a range of molecular masses of the PHPMA block were obtained by controlled radical polymerization on a chip (CRP chip) using a PEO macroinitiator. A series of well‐controlled polymerizations were carried out at different pumping rates or reaction times with a constant ratio of monomer to initiator. The stoichiometry of the reactants was also adjusted by varying relative flow rates to change the reactant concentrations.

A schematic of a CRP chip and SEC traces of the PEO‐b‐PHPMA produced from different pump rates with a 1:100 ratio of initiator to monomer. The dashed peaks are the macroinitiator, PEO‐Br (left), and monomer, HPMA (right).     

A Facile Synthesis of Cleavable Block Copolymers via Tandem Polymerizations of NMRP and ATRP

A functionalized compound, 4‐(2‐bromoisobutyryl)‐2,2,6,6‐tetra‐methylpiperidine‐1‐oxyl (Br‐TEMPO), was synthesized and used to synthesize block copolymers through tandem nitroxide‐mediated radical polymerization (NMRP) and atom transfer radical polymerization (ATRP). First, Br‐TEMPO was used to mediate the polymerization of styrene. The kinetics of polymerization proved a typical “living” nature of the reaction and the effectiveness in the mediation of polymerization of Br‐TEMPO. Then the PS‐Br macroinitiator was used to initiate atom transfer radical polymerization (ATRP). A series of acrylates were initiated by PS‐Br macroinitiators in typical ATRP processes at various conditions. The controlled polymerization of ATRP was also confirmed by molecular weight and kinetic analysis. Several cleavable block copolymers of PS‐b‐P(t‐BA), PS‐b‐P(n‐BA), and PS‐b‐PMA, with different molecular weights, were synthesized via this strategy. Relatively low polydispersities (<1.5) were observed and the molecular weights were in agreement with the theoretical ones. Hydrolysis of PS‐b‐P(t‐BA) was carried out, giving amphiphilic block copolymer PS‐b‐PAA without the cleavage of C‐ON bond or ester bond. All the block copolymers have two T_gs as demonstrated by DSC. A typical cleavable block copolymer of PS‐b‐PMA was cleaved by adding phenylhydrazine at 120°C to produce homopolymers in situ.     

可控自由基聚合与其它活性聚合方法结合制备嵌段共聚物

可控自由基聚合与其它聚合方法结合,可以制备多种类型的嵌段共聚物,因此得到了广泛关注。本文着重介绍可控自由基聚合与离子开环聚合、阴离子聚合、烯类单体的阳离子聚合及其它活性聚合方法结合制备嵌段共聚物的研究现状和进展。     

Amphiphilic diblock,triblock, and star block copolymers by living radical polymerization: Synthesis and aggregation behavior

Copper(I)‐mediated living radical polymerization was used to synthesize amphiphilic block copolymers of poly(n‐butyl methacrylate) [P(n‐BMA)] and poly[(2‐dimethylamino)ethyl methacrylate] (PDMAEMA). Functionalized bromo P(n‐BMA) macroinitiators were prepared from monofunctional, difunctional, and trifunctional initiators: 2‐bromo‐2‐methylpropionic acid 4‐methoxyphenyl ester, 1,4‐(2′‐bromo‐2′‐methyl‐propionate)benzene, and 1,3,5‐(2′‐bromo‐2′‐methylpropionato)benzene. The living nature of the polymerizations involved was investigated in each case, leading to narrow‐polydispersity polymers for which the number‐average molecular weight increased fairly linearly with time with good first‐order kinetics in the monomer. These macroinitiators were subsequently used for the polymerization of (2‐dimethylamino)ethyl methacrylate to obtain well‐defined [P(n‐BMA)_x‐b‐PDMAEMA_y]_z diblock (15,900; polydispersity index = 1.60), triblock (23,200; polydispersity index = 1.24), and star block copolymers (50,700; polydispersity index = 1.46). Amphiphilic block copolymers contained between 60 and 80 mol % hydrophilic PDMAEMA blocks to solubilize them in water. The polymers were quaternized with methyl iodide to render them even more hydrophilic. The aggregation behavior of these copolymers was investigated with fluorescence spectroscopy and dynamic light scattering. For blocks of similar comonomer compositions, the apparent critical aggregation concentration (cac = 3.22–7.13 × 10^?3 g L^?1) and the aggregate size (ca. 65 nm) were both dependent on the copolymer architecture. However, for the same copolymer structure, increasing the hydrophilic PDMAEMA block length had little effect on the cac but resulted in a change in the aggregate size. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 439–450, 2002; DOI 10.1002/pola.10122     

Advances in the Synthesis and Characterization of Polypeptide-Based Hybrid Block Copolymers

Linear polystyrene-block-poly(Z-L-lysine) copolymers with a very narrow molecular weight distribution (polydispersity index < 1.03) could be obtained via the ring-opening polymerization of Z-L-lysine-N-carboxyanhydride using ω-(primary amino hydrochloride)-polystyrenes as macroinitiators in N,N-dimethylformamide as the solvent at 40-80 °C. The block copolymer samples were analyzed by means of NMR, size exclusion chromatography, and analytical ultracentrifugation.     

Selective formation of diblock copolymers using radical trap‐assisted atom transfer radical coupling

Polystyrene (PSt) radicals and poly(methyl acrylate) (PMA) radicals, derived from their monobrominated precursors prepared by atom transfer radical polymerization (ATRP), were formed in the presence of the radical trap 2‐methyl‐2‐nitrosopropane (MNP), selectively forming PSt‐PMA diblock copolymers with an alkoxyamine at the junction between the block segments. This radical trap‐assisted, atom transfer radical coupling (RTA‐ATRC) was performed in a single pot at low temperature (35 °C), while analogous traditional ATRC reactions at this temperature, which lacked the radical trap, resulted in no observed coupling and the PStBr and PMABr precursors were simply recovered. Selective formation of the diblock under RTA‐ATRC conditions is consistent with the PStBr and PMABr having substantially different K_ATRP values, with PSt radicals initially being formed and trapped by the MNP and the PMA radicals being trapped by the in situ‐formed nitroxide end‐capped PSt. The midchain alkoxyamine functionality was confirmed by thermolysis of the diblock copolymer, resulting in recovery of the PSt segment and degradation of the PMA block at the relatively high temperatures (125 °C) required for thermal cleavage. A PSt‐PMA diblock formed by chain extenstion ATRP using PStBr as the macroinitiator (thus lacking the alkoxyamine between the PSt‐PMA segements) was inert to thermolysis. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3619–3626     

Atom Transfer Radical Polymerization with Polypeptide Initiators: A General Approach to Block Copolymers of Sequence‐Defined Polypeptides and Synthetic Polymers

Summary: A novel two‐step polymerization strategy allowing the integration of sequence‐defined oligopeptides into synthetic polymers has been demonstrated by the successful synthesis of an oligopeptide‐block‐poly(n‐butyl acrylate) copolymer. The approach utilizes a solid‐phase supported synthesis of an oligopeptide macroinitiator (SPPS) followed by solution‐phase atom transfer radical polymerization (ATRP) initiated by the oligopeptide macroinitiator. The resulting block copolymer exhibited a low (1.19) and a controllable .

Poly(n‐butyl acrylate)‐block‐oligopeptide.     

Copolymers Containing Phosphorescent Iridium(III) Complexes Obtained by Free and Controlled Radical Polymerization Techniques

A methacrylate‐functionalized phosphorescent Ir(III)‐complex has been synthesized, characterized, and applied as a monomer in radical copolymerizations. Together with methyl methacrylate, the complex has been copolymerized under free radical polymerization conditions. Aiming for host‐guest‐systems, applicable e.g. in organic light emitting devices (OLEDs), the complex was further copolymerized with a methacrylate‐functionalized carbazole derivative using the atom transfer radical polymerization technique. Applying gel permeation chromatography, in combination with a photodiode array detector, could clearly prove the formation of the copolymers. The optical properties of the photoactive monomers as well as the copolymers were investigated by absorption and emission spectroscopy (in solution). For the carbazole‐copolymer, the emission originates almost exclusively from the complex. This provides evidence of an efficient intrachain energy transfer, which makes the system an interesting candidate for potential OLED applications.

     

Synthesis of Dendritic-Linear Block Copolymers by Atom Transfer Radical Polymerization

Polymers and copolymers with complex, yet well-defined architectures are drawing significant attentions in the search for materials with excellent properties. Of these macromolecular structures, dendritic-linear block copolymers consisting of covalently bound linear and dendritic segments have shown interesting solution, solid-state, and interfacial properties. As a novel polymerization approach, atom transfer radical polymerization (ATRP) has been attracting increasing interest recently, sin…     

Synthesis of AB diblock copolymers by atom-transfer radical polymerization (ATRP) and living polymerization of alpha-amino acid-N-carboxyanhydrides

The synthesis of poly(methyl acrylate)-block-poly(gamma-benzyl-L-glutamate) (PMA-b-PBLG) diblock copolymers, using atom-transfer radical polymerization (ATRP) of methyl acrylate and living polymerization of gamma-benzyl-L-glutamate-N-carboxyanhydride (Glu-NCA) is described. Amido-amidate nickelacycle end groups were incorporated onto amino-terminated poly(methyl acrylates), and the resulting complexes were successfully used as macroinitiators for the growth of polypeptide segments. This method allows the controlled preparation of polypeptide-block-poly(methyl acrylate) diblock architectures with control over polypeptide chain length and without the formation of homopolypeptide contaminants.     

乳液原子转移自由基聚合*

原子转移自由基聚合(ATRP)应用于乳液聚合体系的主要挑战在于如何同时保证乳液的稳定性和聚合反应的可控性。本文主要对乳液ATRP体系中影响聚合反应可控性和乳液稳定性的各种因素、乳液ATRP的机理和乳液ATRP的应用等方面进行了综述。表面活性剂亲水亲油性及其亲水亲油基团的化学性质、催化剂/配体在油/水两相之间的分配行为、引发剂的溶解性、反应温度以及各组分的浓度是影响反应可控性和乳液稳定性的主要因素。各组分在油/水两相中的分配行为使得乳液ATRP的机理比传统乳液聚合更加复杂。乳液原子转移自由基聚合结合了活性自由基聚合和乳液聚合的优点,在理论研究和工业生产上具有很大的应用前景。     

Synthesis of Block Copolymers with a Pentasilane Core

We report a new method for the synthesis of block copolymers with a pentasilane core by the polymerization of alkyl methacrylate monomers using the pentasilyl dianion as an initiator. The polymerization proceeded with living features and yielded the corresponding block copolymers with controlled molecular weights. The amphiphilic block copolymer was obtained by the polymer reaction, and it formed sphere‐like aggregates in MeOH/H₂O solution.

     

Synthesis and thiol-responsive degradation of polylactide-based block copolymers having disulfide junctions using ATRP and ROP

A new method to synthesize a variety of well-controlled polylactide (PLA)-based block copolymers having disulfide linkages at block junctions (PLA-ss-PATRPs) was investigated. The method uses a combination of ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP) that initiates the synthesis of a new disulfide-labeled double-head initiator having both terminal OH and Br groups (HO-ss-iBuBr). The amount of tin catalyst and polymerization time significantly influenced the control of ROP initiated with HO-ss-iBuBr. A series of ATRP of various methacrylates as well as acrylate and styrene in the presence of the resulting PLA-ss-iBuBr macroinitiators proceeded in a living manner. These well-controlled PLA-ss-PATRPs were further characterized for thermal properties using differential scanning calorimetry and thiol-responsive degradation upon the cleavage of disulfide linkages. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym. Chem. 2013, 51, 3071–3080