Article

Simultaneous step-growth and chain-growth cationic polymerization of styrenic monomers bearing carbazolyl groups

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Abstract

Cationic polymerization of two styrene derivatives containing carbazole moiety with different linking topology, 9-(4-vinylphenyl)carbazole (M1) and 3-(4-vinylphenyl)-9-ethylcarbazole (M2), using 1-chloro-1-phenylethane (PhEtCl)/SnCl4 initiating system has been investigated. It was shown that polymerization of M1, which is characterized by higher electron density on the carbon at the 3 position of carbazolyl group than on vinyl group, proceeds predominantly via step-growth (SG) pathway through addition of protonated monomer/oligomers to 3-position of carbazolyl group (electrophilic aromatic substitution). On the contrary, M2, in which 3-position of carbazolyl group is protected via introduction of 4-vinylphenyl group, polymerized predominantly via chain-growth (CG) pathway through addition of carbocation to double bond of monomer. The polymers synthesized via SG mechanism showed different photophysical characteristics in comparison with corresponding monomer, while in case of polymers prepared via CG mechanism the polymer and monomer have the same absorption and fluorescence profiles.

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... However, in all these examples low molecular weight polymers (M n = 1810-5800 g mol −1 ) with high polydispersity (Đ ≤ 8.8) were generated due to the uncontrolled character of the process. Other families of carbazole-containing monomers possessing acrylate [11,12], methacrylate [13][14][15] and styrene [16][17][18] moieties were also synthesized. These monomers were successfully polymerized through conventional radical [12][13][14][15]17], anionic [11,18] and cationic [16] mechanisms affording ill-defined polymers typically with high polydispersity and without control over their molecular weight. ...
... Other families of carbazole-containing monomers possessing acrylate [11,12], methacrylate [13][14][15] and styrene [16][17][18] moieties were also synthesized. These monomers were successfully polymerized through conventional radical [12][13][14][15]17], anionic [11,18] and cationic [16] mechanisms affording ill-defined polymers typically with high polydispersity and without control over their molecular weight. ...
... The main advantage of this approach is the possibility to prepare cross-linkable star-shaped polymers with photoactive end groups, which are promising host materials for solution processable polymeric light emitting devices [33]. However, only monomers bearing electron donating groups could be polymerized using this approach, while the presence of heteroatom (sulfur) negatively influences the thermal properties (T ID ) of the corresponding polymers [16,33]. ...
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Atom-transfer radical polymerization of 9-(4-vinylphenyl)carbazole (M1) and 9-(2,3,5,6-tetrafluoro-4-vinylphenyl)carbazole (M2) has been investigated using CuCl/N,N,N′,N′′,N′′-pentamethyldiethylenetriamine as catalyst and ethyl 2-bromoisobutyrate as an initiator. The polymerization of the monomers proceeded in a living fashion affording polymers with controlled molecular weight (Mn = 5000 g mol⁻¹ to 32000 g mol⁻¹) and relatively low polydispersity (Đ = 1.2–1.5). The kinetic investigations showed that M2 polymerized at the faster rate as compared to M1. Block copolymers were successfully prepared starting from the polymerization of more reactive M2 followed by addition of M1. The same initiating system also induced living radical copolymerization of these monomers giving random copolymers. Usage of tetrafunctional initiator pentaerythritol tetrakis(2-bromoisobutyrate) in conjunction with CuCl/N,N,N′,N′′,N′′-pentamethyldiethylenetriamine as catalyst allowed to synthesize star-shaped linear and random copolymers from M1 and M2 with controlled molar mass (up to Mn = 25000 g mol⁻¹) and low polydispersity (Đ < 1.5). The thermal, photophysical and electrochemical properties of the synthesized linear and star-shaped polymers and copolymers were estimated. It was shown that photophysical properties of copolymers can be tuned by changing the copolymer composition.
... In order to tune electrochemical and photophysical properties of poly(N-vinylcarbazole), a great variety of polymers containing carbazole moieties in the side chain were successfully synthesized [5][6][7]. Firstly, poly(meth)acrylates and polystyrenes with pendant carbozolyl group were mainly synthesized through conventional radical mechanism [8][9][10][11][12], although there are several reports where such kind of polymers have been successfully obtained by anionic [13,14] and cationic [15] mechanisms. However, it was difficult to control the molecular weight and architecture of the synthesized polymers that significantly complicated the finding of the correlation between polymer structure and its electronic and photonic properties. ...
... All calculations were performed as described [15]. All optimized structures were checked to be minima, with no imaginary frequencies. ...
... In addition to the chain-growth polymerization with the participation of vinyl groups, a stepgrowth polymerization with the participation of vinyl groups and aromatic moieties apparently takes place. The combination of chain-growth and step-growth polymerizations was recently observed for the polymerization of 9-(4-vinylphenyl)carbazole in the presence of (PhEtCl)/SnCl 4 initiation system [50]. IR spectra of the polymerization products of monomers 7-9 show the decreased intensity of Fig. 4 FT-IR spectra of monomers 7-9 and of their products of polymerization the signals of vinyl groups at 908-907 cm −1 compared to those of the spectra of the monomers (Fig. 4). ...
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All polymerization reactions are categorized into two large different families, chain- and step-growth polymerizations, which are typically incompatible. Here, we report the simultaneous chain- and step-growth polymerization via the metal-catalyzed radical copolymerization of conjugated vinyl monomers and designed monomers possessing unconjugated C horizontal lineC and active C-Cl bonds. Especially, almost ideal linear random copolymers containing both vinyl polymer and polyester units in a single polymer chain were formed by the CuCl/1,1,4,7,10,10-hexamethyltriethylenetetramine- or RuCp*Cl(PPh(3))(2)-catalyzed copolymerization of methyl acrylate (MA) for the chain-growth polymerization and 3-butenyl 2-chloropropionate (1) for the step-growth polymerization. In contrast, other transition metal catalysts, such as CuCl with tris[2-(dimethylamino)ethyl]amine or N,N,N',N'',N''-pentamethyldiethylenetriamine and FeCl(2)/PnBu(3), resulted in branched structures via the concomitant chain-growth copolymerization of 1 with MA. The polymerization mechanism was studied in detail by NMR and MALDI-TOF-MS analyses of the polymerizations as well as the model reactions. Furthermore, a series of copolymers changing from random to multiblock polymer structures were obtained by varying the feed ratios of the two monomers. These copolymers can be easily degraded into lower molecular weight oligomers or polymers via methanolysis of the ester-linkages in the main chain using sodium carbonate.
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Polymer latexes are easily prepared on a multimillion ton scale in industry using free radical initiated emulsion and suspension polymerizations in water, a cheap, nonviscous, heat-controlling, and environmentally benign solvent. Until recently, researchers had done little investigation into ionic polymerization because even a small amount of water would easily deactivate the conventional catalysts used in these processes. In the last decade, however, cationic polymerization in aqueous media has emerged as a new and attractive method for controlling the polymerization reactions using mild experimental conditions.
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Advances in living polymerization initiators, including the design and synthesis of a variety of new polymers, with a focus on the most recent developments, are reviewed. The fabrication of macromolecular aggregates that display various functions and properties will become increasingly important in the development of polymer synthesis. To accomplish this, it will be necessary to design and synthesize polymers in which the primary structure, including monomer sequences and stereoregularity, is precisely controlled. The importance of the choice of acid catalysts (activator) was shown in cationic polymerization of styrene and its derivatives. It was then known that molecular weight of product polymers became higher when a polar solvent was used. Successful catalytic processes were achieved using metal triflates in the 1990s. Efficient acylation proceeded with a catalytic amount of triflates of Ti, 58 Hf, 59,60 Sc, 61,62 and lanthanides. The development of new polymerization catalyst systems that will serve as the basis for this will be indispensable.
  • K Nakabayashi
  • H Mori
K. Nakabayashi, H. Mori, Int. J. Polym. Sci. 2012 (2012). Article ID 170912.
  • C J Hu
  • R Oshima
  • S Sato
  • M Seno
C.J. Hu, R. Oshima, S. Sato, M. Seno, J. Polym. Sci. Part C.Polym. Lett. 26 (1988) 441e446.
  • F S Du
  • Z C Li
  • W Hong
  • Q Y Cao
  • F M Li
F.S. Du, Z.C. Li, W. Hong, Q.Y. Cao, F.M. Li, J. Polym. Sci. Part A Polym. Chem. 38 (2000) 679e688.
  • T Kanbara
  • Y Yokokawa
  • K Hasegawa
T. Kanbara, Y. Yokokawa, K. Hasegawa, J. Polym. Sci. Part A Polym. Chem. 38 (2000) 28e34.
  • Y.-S Cho
  • S.-W Kim
  • C.-S Ihn
  • J.-S Lee
Y.-S. Cho, S.-W. Kim, C.-S. Ihn, J.-S. Lee, Polymer 42 (2001) 7611e7616.
  • C Bunel
  • S Cohen
  • J P Laguerre
C. Bunel, S. Cohen, J.P. Laguerre, E. Marechal, Polym. J. 7 (1975) 320e325.
  • P Blin
  • C Bunel
P. Blin, C. Bunel, E. Marechal, J. Polym. Sci. Polym. Chem. Ed. 19 (1981) 891e896.
  • L Wockel
  • A Seifert
  • C Mende
  • I Roth-Panke
  • L Kroll
  • S Spange
L. Wockel, A. Seifert, C. Mende, I. Roth-Panke, L. Kroll, S. Spange, Polym. Chem. 8 (2017) 404e413.
  • T Hashimoto
  • K Ishizuka
  • A Umehara
  • T Kodaira
T. Hashimoto, K. Ishizuka, A. Umehara, T. Kodaira, J. Polym. Sci. Part A Polym. Chem. 40 (2002) 4053e4064.
  • S Hohre
  • S Spange
  • W Schrepp
S. Hohre, S. Spange, W. Schrepp, Polym. Bull. 47 (2001) 31e37.
  • A Gandini
  • R Alvarez
A. Gandini, R. Alvarez, J. Polym. Sci. Symp. 56 (1976) 79e90.
  • R Alvarez
  • A Gandini
  • R Martinez
R. Alvarez, A. Gandini, R. Martinez, Macromol. Chem. Phys. 183 (1982) 2399e2413.
  • K Kim
  • Y K Fang
  • W Kwon
  • S Pyo
  • W C Chen
  • M Ree
K. Kim, Y.K. Fang, W. Kwon, S. Pyo, W.C. Chen, M. Ree, J. Mat. Chem. C 1 (2013) 4858e4868.
  • A D Becke
A.D. Becke, J. Chem. Phys. 98 (1993) 5648e5652.
  • M T Cances
  • B Mennucci
  • J Tomasi
M.T. Cances, B. Mennucci, J. Tomasi, J. Chem. Phys. 107 (1997) 3032e3041.
  • T Higashimura
  • Y Ishihama
  • M Sawamoto
T. Higashimura, Y. Ishihama, M. Sawamoto, Macromolecules 26 (1993) 744e751;
  • S V Kostjuk
  • A Yu Dubovik
  • I V Vasilenko
  • V P Mardykin
  • L V Gaponik
  • F N Kaputsky
  • L M Antipin
S.V. Kostjuk, A. Yu Dubovik, I.V. Vasilenko, V.P. Mardykin, L.V. Gaponik, F.N. Kaputsky, L.M. Antipin, Polym. Bull. 52 (2004) 227e234;
  • G Kaszas
  • J E Puskas
  • J P Kennedy
  • W G Hager
G. Kaszas, J.E. Puskas, J.P. Kennedy, W.G. Hager, J. Polym. Sci. Part A Polym. Chem. 29 (1991) 421e426;
  • Z Fodor
  • M Gyor
  • H C Wang
  • R Faust
Z. Fodor, M. Gyor, H.C. Wang, R. Faust, J. Macromol. Sci.Pure Appl. Chem. A30 (1993) 349e363.