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1.
Vincenzo Busico Philippe Carbonniere Roberta Cipullo Roberta Pellecchia John R. Severn Giovanni Talarico 《Macromolecular rapid communications》2007,28(10):1128-1134
Suitably activated, (Cp*){N(tBu)C(Me)N(Et)}ZrMe2 is known to initiate the ‘living’ and isotactic‐selective polymerization of alk‐1‐enes, and it can be used to synthesize block copolymers and stereoblock polymers. We report a full molecular kinetic investigation of propene, but‐1‐ene, and hex‐1‐ene polymerization with a MAO‐activated catalyst system. By combining NMR microstructural polymer analysis with QM modeling of the active species, the complicated regio‐ and stereochemistry of the polyinsertion process, as well as the active chain‐transfer pathways, are investigated. The perspectives and limitations of this catalyst for application in (stereo)block polymerizations are discussed.
2.
A series of well‐defined rod‐coil PAA‐b‐DPS block copolymers, containing Fréchet‐type dendronized polystyrene (DPS) with different generation as a rod‐like hydrophobic block and poly(acrylic acid) (PAA) as a hydrophilic coil were synthesized. The procedure included the following steps: the precursor PMA‐b‐DPS copolymer was prepared through ATRP of Fréchet‐type dendritic styrene macromonomer bearing the first to the third generation (G1–G3), respectively, initiated by poly(methyl acrylate) (PMA‐Br). Then, by converting PMA into PAA by subsequent hydrolysis, the targeted amphiphilic copolymers were obtained. Moreover, by using the rod‐coil amphiphiles as building blocks, large compound micelles and vesicles were formed in a binary solvent mixture of DMF/H2O. Morphological changes in self‐assembly showed dependence on the length of the dendronized block.
3.
Edgar Espinosa Mathias Glassner Christophe Boisson Christopher Barner‐Kowollik Franck D'Agosto 《Macromolecular rapid communications》2011,32(18):1447-1453
In the current contribution it is demonstrated – for the first time – that poly(ethylene) ( = 1 400 as well as 2 800 g · mol−1, PDI = 1.2) can be readily equipped with highly reactive cyclopentadienyl (Cp) end groups. The Cp terminal poly(ethylene) can subsequently be reacted in an efficient hetero Diels‐Alder (HDA) reaction with macromolecules (poly(isobornyl acrylate) ( = 4 600 g · mol−1, PDI = 1.10) and poly(styrene) ( = 6 300 g · mol−1, PDI = 1.13) featuring strongly electron withdrawing thiocarbonyl thio end groups, prepared via reversible addition fragmentation chain transfer (RAFT) polymerization employing benzylpyridin‐2‐yldithioformate (BPDF) as transfer agent. The resulting block copolymers have been analyzed via high‐temperature size exclusion chromatography (SEC) as well as nuclear magnetic resonance (NMR) spectroscopy. The current system allows for the removal of the excess of the non‐poly(ethylene) containing segment via filtration of the poly(ethylene)‐containing block copolymer. However, the reaction temperatures need to be judiciously selected. Characterization of the generated block copolymers at elevated temperatures can lead – depending on the block copolymer type – to the occurrence of retro Diels‐Alder processes. The present study thus demonstrates that RAFT‐HDA ligation can be effectively employed for the generation of block copolymers containing poly(ethylene) segments.
4.
Martina H. Stenzel Ling Zhang Wilhelm T. S. Huck 《Macromolecular rapid communications》2006,27(14):1121-1126
Summary: Stimuli‐responsive glycopolymer brushes composed of N‐acryloyl glucosamine (AGA) and N‐isopropylacrylamide (NIPAAm) were prepared using RAFT polymerization. The RAFT agent was immobilized on the surface of a treated silicon waver via covalent attachment using the Z‐group. PAGA and PNIPAAm brushes showed a linear increase in brush thickness with the consumption of monomer in solution. The polymers generated in solution confirm the living behavior with the molecular weight increasing linearly with monomer conversion while the molecular weight distribution remains narrow. Additionally, the ability of PAGA brushes to grow further in the presence of NIPAAm reveals the presence of an active RAFT end group indicative of a living system. PAGA and PNIPAAm homopolymer brushes up to 30 nm were grown using this technique. PAGA brushes were utilized for further chain extension to generate stimuli‐responsive brushes with block structures of PAGA and PNIPAAm. The PAGA‐block‐PNIPAAm brushes were found to grow in size with the consumption of NIPAAm. Contact angle measurements confirm the suggested mechanism showing that the second monomer is incorporated between the first layer and the silicon surface as expected using the Z‐group approach.
5.
Tomohiro Masukawa Akihiro Yokoyama Tsutomu Yokozawa 《Macromolecular rapid communications》2009,30(16):1413-1418
Well‐defined diblock copolymers composed of poly(N‐octylbenzamide) and polystyrene were synthesized by reversible addition‐fragmentation chain transfer (RAFT) polymerization of styrene with a polyamide chain transfer agent (CTA) prepared via chain‐growth condensation polymerization. Synthesis of a dithioester‐type macro‐CTA possessing the polyamide segment as an activating group was unsatisfactory due to side reactions and incomplete introduction of the benzyl dithiocarbonyl unit. On the other hand, a dithiobenzoate‐CTA containing poly(N‐octylbenzamide) as a radical leaving group was easily synthesized, and the RAFT polymerization of styrene with this CTA afforded poly(N‐octylbenzamide)‐block‐polystyrene with controlled molecular weight and narrow polydispersity.
6.
Leonie Barner Thomas P. Davis Martina H. Stenzel Christopher Barner‐Kowollik 《Macromolecular rapid communications》2007,28(5):539-559
Reversible addition–fragmentation chain transfer (RAFT) chemistry can be effectively employed to construct macromolecular architectures of varying topologies. The present article explores the principle design routes to star, block, and comb polymers in the context of theoretical design criteria for the so‐called Z‐ and R‐group approaches. The specific advantages and disadvantages of each approach are underpinned by selected examples generated in the CAMD laboratories. In particular, we demonstrate how the modeling of full molecular weight distributions can be employed to guide the synthetic effort. We further explore the theory and practice of generating amphiphilic block copolymer structures and their self‐assembly. In addition, the article foreshadows how modern synthetic techniques that combine RAFT chemistry with highly orthogonal click chemistry can be employed as a powerful tool that furthers the enhancement of macromolecular design possibilities to generate block (star) copolymers of monomers with extremely disparate reactivities. Finally, the ability of RAFT chemistry to modify the surface of well‐defined nano‐ and microspheres as devices in biomedical application is detailed.
7.
Jingquan Liu Volga Bulmus Christopher Barner‐Kowollik Martina H. Stenzel Thomas P. Davis 《Macromolecular rapid communications》2007,28(3):305-314
A trithiocarbonate RAFT agent was modified with a pyridyl disulfide group and used in the direct synthesis of endgroup pyridyl disulfide‐functionalized homo‐ and amphiphilic block copolymers of oligo(ethyleneglycol) acrylate (PEG‐A) and butyl acrylate (BA). Both the homo‐ and copolymerizations were found to be well controlled via the RAFT mechanism. The NMR analysis indicated that both the homopolymers of PEG‐A and the amphiphilic diblock copolymers of PEG‐A and BA possessed pyridyl disulfide terminal groups. A UV‐Vis absorption test revealed that the pyridyl disulfide endgroup of the polymer could be efficiently used to couple thiol‐bearing molecules to the polymer without the need for any post‐polymerization modification. This communication presents the first efficient direct synthesis of thiol‐reactive endgroup‐functionalized well‐defined polymers via the RAFT technique.
8.
Yun Wang Qibao Dong Yanxue Wang Hu Wang Guang Li Ruke Bai 《Macromolecular rapid communications》2010,31(20):1816-1821
A Y‐shaped amphiphilic fluorinated monomer, 1‐(1H,1H,2H,2H‐perfluorodecyloxy)‐3‐(3,6,9‐trioxadecyloxy)‐propan‐2‐yl acrylate has been synthesized and its polymerization by reversible addition–fragmentation chain transfer (RAFT) homopolymerization has been investigated. The results show that the molecular weights of the polymers are controlled and all the molecular weight distributions are lower than 1.4. Well‐defined copolymers with 2‐(N,N‐dimethylamino)ethyl methacrylate have been prepared by RAFT polymerization, and the surface properties of the block and random copolymers have been examined by contact angle measurement for water and hexadecane. It has been found that the surfaces of the block copolymers simultaneously exhibit excellent anti‐fog and oil‐repellent properties.
9.
Leena Nebhani Sebastian Sinnwell Andrew J. Inglis Martina H. Stenzel Christopher Barner‐Kowollik Leonie Barner 《Macromolecular rapid communications》2008,29(17):1431-1437
A combination of reversible addition fragmentation chain transfer (RAFT) polymerization and hetero Diels‐Alder (HDA) chemistry has been utilized to successfully generate functional core‐shell microspheres. Initially, precipitation polymerization in conjunction with the RAFT technique has been employed to synthesize divinylbenzene (DVB) microspheres with surface expressed RAFT groups. Subsequently, HDA cycloaddition has been performed under mild reaction conditions (50 °C, 24 h) with a diene‐functionalized poly(ε‐caprolactone) (PCL). While the successful grafting is immediately evident by optical inspection of the microspheres (color change from purple to white), X‐ray photoelectron spectroscopy (XPS), and attenuated total reflectance spectroscopy (ATR) were additionally employed to characterize the chemical composition and surface functionalization of the microspheres. Further, confocal microscopy was used to confirm the presence of grafted PCL chains after labeling them with rhodamine B.
10.
Wing Yan Tam Chris S. K. Mak Alan Man Ching Ng Aleksandra B. Djurii Wai Kin Chan 《Macromolecular rapid communications》2009,30(8):622-626
The synthesis of poly(N‐vinylcarbazole)‐based block copolymers functionalized with rhenium diimine complexes or pendant terpyridine ligands is reported. The copolymers are synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization, and they exhibit interesting morphological properties as a result of the phase separation between different blocks. The rhenium complex polymer block may function as a photosensitizer, while the terpyridine‐containing polymer block can be used as the template for nanofabrication by selective deposition of zinc complexes.
11.
Ling Zhang Julien Bernard Thomas P. Davis Christopher Barner‐Kowollik Martina H. Stenzel 《Macromolecular rapid communications》2008,29(2):123-129
A thermoresponsive block copolymer, namely poly(acryloyl glucosamine)‐block‐poly(N‐isopropylacryamide) (PAGA180‐b‐PNIPAAM350) was simultaneously self‐assembled and crosslinked in aqueous medium via RAFT polymerization at 60 °C to afford core‐crosslinked micelles exhibiting a glycopolymer corona and a PNIPAAM stimuli‐responsive core. An acid‐labile crosslinking agent, 3,9‐divinyl‐2,4,8,10‐tetraoxaspiro[5.5]undecane, was employed to generate thermosensitive and acid‐degradable core‐shell nanoparticles. Stable against degradation at pH = 6 and 8.2, the resulting core crosslinked micelles readily hydrolyzed into well‐defined free block copolymers at lower pH (30 min and 12 h respectively at pH = 2 and 4).
12.
Isabelle Chaduc Wenjing Zhang Jutta Rieger Muriel Lansalot Franck D'Agosto Bernadette Charleux 《Macromolecular rapid communications》2011,32(16):1270-1276
The syntheses of amphiphilic block copolymers are successfully performed in water by chain extension of hydrophilic macromolecules with styrene at 80 °C. The employed strategy is a one‐pot procedure in which poly(acrylic acid), poly(methacrylic acid) or poly(methacrylic acid‐co‐poly(ethylene oxide) methyl ether methacrylate) macroRAFTs are first formed in water using 4‐cyano‐4‐thiothiopropylsulfanyl pentanoic acid (CTPPA) as a chain transfer agent. The resulting macroRAFTs are then directly used without further purification for the RAFT polymerization of styrene in water in the same reactor. This simple and straightforward strategy leads to a very good control of the resulting amphiphilic block copolymers.
13.
Jean‐Marc Schumers Charles‐Andr Fustin Jean‐Franois Gohy 《Macromolecular rapid communications》2010,31(18):1588-1607
Stimuli‐responsive polymers are the subject of intense research because they are able to show responses to various environmental changes. Among those stimuli, light has attracted much attention since it can be localized in time and space and it can also be triggered from outside of the system. In this paper, we review light‐responsive block copolymers (LRBCs) that combine characteristic features of block copolymers, e.g., self‐assembly behavior, and light‐responsive systems. The different photo‐responsive moieties that have been incorporated so far in block copolymers as well as the proposed applications are discussed.
14.
Marcin Florczak Jan Libiszowski Jaroslav Mosnacek Andrzej Duda Stanislaw Penczek 《Macromolecular rapid communications》2007,28(13):1385-1391
L,L ‐lactide (LA) and ε‐caprolactone (CL) block copolymers have been prepared by initiating the poly(ε‐caprolactone) (PCL) block growth with living poly(L,L ‐lactide) (PLA*). In the previous attempts to prepare block copolymers this way only random copolyesters were obtained because the PLA* + CL cross‐propagation rate was lower than that of the PLA–CL* + PLA transesterification. The present paper shows that application of Al‐alkoxide active centers that bear bulky diphenolate ligands results in efficient suppression of the transesterification. Thus, the corresponding well‐defined di‐ and triblock copolymers could be prepared.
15.
Xing Xiao Ya‐qin Fu Jian‐jun Zhou Zhi‐shan Bo Lin Li Chi‐Ming Chan 《Macromolecular rapid communications》2007,28(9):1003-1009
A functional coil–rod–coil triblock copolymer containing a terfluorene unit as the rigid segment and poly(N‐isopropylacrylamide) (PNIPAAm) as the flexible block was successfully synthesized via reversible addition–fragmentation chain‐transfer (RAFT) polymerization using terfluorene‐based dithioester as the RAFT agent. The temperature‐responsive optical properties were investigated with the aid of dynamic light scattering and fluorescence techniques. Additionally, the relationship between the optical properties and the reversible phase transition of the doping system formed by blending the copolymer with tetraphenylporphine tetrasulfonic acid was studied. Above the lower critical solution temperature, the energy transfer efficiency decreased as a result of the globule–to–coil transition from PNIPAAm segments. The result indicates that these copolymers have a potential to be used as responsive fluorescent probes in facile detection of dye‐labeled biopolymers.
16.
Till Gruendling Kim K. Oehlenschlaeger Elena Frick Mathias Glassner Christina Schmid Christopher Barner‐Kowollik 《Macromolecular rapid communications》2011,32(11):807-812
Shining a light on click chemistry: The use of UV‐radiation as trigger signal provides a facile means to obtain spatial and temporal control over polymer conjugation reactions in addition to providing a further means of achieving orthogonality in click transformations. In the current contribution, UV‐radiation was employed to induce a highly efficient Diels–Alder conjugation of polymeric building blocks via the photo‐induced in situ formation of highly reactive cis‐dienes from a 2‐methylbenzophenone precursor.
17.
Nawel Khelfallah Nikhil Gunari Karl Fischer Giorgos Gkogkas Nikos Hadjichristidis Manfred Schmidt 《Macromolecular rapid communications》2005,26(21):1693-1697
Summary: Amphiphilic cylindrical brush‐coil block copolymers consisting of a polystyrene coil and a cylindrical brush block with poly(acrylic acid) side chains are prepared by ATRP of t‐butylacrylate from a block comacroinitiator. Upon acidolysis of the poly(t‐butylacrylate), water‐soluble polymers were obtained that were observed to form micelles consisting of 4–5 block copolymers on average in aqueous solution. The star‐like nature of such micelles was clearly visualized by scanning force microscopy.
18.
Gaojian Chen Xiulin Zhu Jian Zhu Zhenping Cheng 《Macromolecular rapid communications》2004,25(7):818-824
Summary: Plasma‐initiated controlled/living radical polymerization of methyl methacrylate (MMA) was carried out in the presence of 2‐cyanoprop‐2‐yl 1‐dithionaphthalate. Well‐defined poly(methyl methacrylate) (PMMA), with a narrow polydispersity, could be synthesized. The polymerization is proposed to occur via a RAFT mechanism. Chain‐extension reactions were also successfully carried out to obtain higher molecular weight PMMA and PMMA‐block‐PSt copolymer.
19.
Xi Wang Xing Xiao Xiaohong Wang Jianjun Zhou Lin Li Jun Xu Baohua Guo 《Macromolecular rapid communications》2007,28(7):828-833
Poly(2‐hydroxyethyl methacrylate)‐block‐poly(N‐isopropylacrylamide) (PHEMA‐b‐PNIPAM) was prepared by controlled surface‐initiated ATRP from silicon substrates, and the resulting block copolymers were successfully converted into the corresponding PSEMA‐b‐PNIPAM by esterification of the hydroxy groups on the PHEMA block using excess of succinic anhydride. The PSEMA‐b‐PNIPAM block copolymer brushes respond to both temperature and pH stimuli. The double‐responsive behavior of the block copolymer brushes in solution was investigated by height imaging and force–distance measurements of AFM. The results clearly show the responsive behavior of the smart block copolymer brushes.
20.
Jie Zhang Zhenning Yu Xinhua Wan Xiaofang Chen Qifeng Zhou 《Macromolecular rapid communications》2005,26(15):1241-1245
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.