Atom Transfer Radical Polymerization Of Acrylonitrile Research Articles

Photoinduced ATRP of acrylonitrile with aniline as photoinitiator

ABSTRACTPhoto-mediated atom transfer radical polymerization (ATRP) of acrylonitrile (AN) was carried out at 25°C in N,N-dimethyl formamide (DMF) with aniline as photoinitiator. Polyacrylonitrile (PAN) with predictable average molecular weight and narrow molecular weight distribution was synthesized with 2-Bromopropionitrile (BPN) as ATRP initiator and FeCl3·6H2O/Triphenylphosphine (PPh3) as the catalyst. The obtained kinetics showed that the photoinduced Fe-mediated ATRP of AN provided a route to synthesize well defined PAN with narrow molecular weight distribution (Mw/Mn). The living character of photoinduced Fe-mediated ATRP of AN was verified by the linear increase of molecular weights with monomer conversion and the molecular weights are in good agreement with the theoretic values. In addition, the chain extension experiments were successfully conducted under the same conditions. The periodic light on-off process was investigated for the photoinduced Fe-mediated ATRP of AN. The obtained PAN was characterized by 1H nuclear magnetic resonance and gel permeation chromatography. The brominated PAN was used to perform chain-extension with AN as macroinitiator in order to verify the living nature of photoinduced ATRP of AN-Br.

Preparation of mesoporous silica particles with carbon-coated pore walls: selective grafting of polyacrylonitrile onto the inner surface of a mesoporous silica particle and carbonization

We prepared mesoporous silica particles with inner surfaces coated with carbonaceous materials. A functional mesoporous silica particle (FSP) having methoxy urethane moieties tethered to the pore wall was synthesized by the template method from tetraethoxysilane (TEOS) and an amphiphilic organotriethoxysilane bearing a thermally reversible urethane bond. The surfactant template molecules in the pores were extracted in methanol in the presence of HCl. An atom transfer radical polymerization (ATRP) initiator was selectively introduced onto the inner surface by the reaction of 2-hydroxyethyl-2-bromo-2-methylpropanoate with the methoxy urethane group. The ATRP of acrylonitrile was carried out inside the pores to yield polyacrylonitrile (PAN) grafted to the pore wall. Subsequent pyrolysis of PAN resulted in the formation of mesoporous silica particles with carbon-coated pore walls. The property changes in the inner surface were investigated by analyzing the hydrogen adsorption. Carbonized silica particles showed an improved hydrogen adsorption capacity of 1.26 wt% at 1 bar and 77 K compared to 0.46 wt% for FSP.

Preparation of polyacrylonitrile with improved isotacticity and low polydispersity

AbstractThe preparation of a polymer with both low polydispersity and high tacticity is one current challenge we face and warrants thorough investigation from both the theoretical and experimental standpoints. In this study, we synthesized polyacrylonitrile (PAN) with simultaneously controlled molecular weight and tacticity on the basis of the strategy of the atom transfer radical polymerization (ATRP) of acrylonitrile (AN) in the presence of Lewis acids. A new combined initiation system of 3‐bromopropionitrile (3‐BPN)/Cu2O/N,N,N′,N′‐tetramethylethylenediamine (TMEDA) was used for the ATRP of AN for the first time. When the polymerization was performed with the ratio [AN]0/[Initiator]0/[Cu2O]0/[TMEDA]0 = 190/1/0.5/1.5 (where the subscript 0 indicates the initial conditions) in ethylene carbonate at 60°C for 48 h, the polydispersity of the obtained PAN was 1.13, and the molecular weight was up to 13,710. The polymerization kinetics results show that the polymerizations proceeded with a living/controlled nature except that an induction period existed during the polymerization process because of the lower initiating activity of 3‐BPN. Also, two kinds of Lewis acid, AlCl3 and yttrium trifluororomethanesulflnate, were used in the ATRP system of AN for the tacticity control. The addition of 0.01 equiv (relative to AN) of the Lewis acid AlCl3 in the polymerization afforded PAN with an improved isotacticity [meso/meso triad (mm) = 0.32] and a very narrow polydispersity (1.06). © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Synthesis of Well‐Defined Rod‐Coil Diblock Copolymer of Aromatic Polyether and Polyacrylonitrile by Chain‐Growth Condensation Polymerization and Atom Transfer Radical Polymerization

AbstractThe synthesis of diblock copolymers of aromatic polyether and polyacrylonitrile (PAN) was conducted by chain‐growth condensation polymerization (CGCP) and atom transfer radical polymerization (ATRP) from an orthogonal initiator. When CGCP for aromatic polyether was carried out from a PAN macroinitiator obtained by ATRP with an orthogonal initiator, decomposition of the PAN backbone occurred. However, when ATRP of acrylonitrile was conducted from an aromatic polyether macroinitiator obtained by CGCP followed by introduction of an ATRP initiator unit, the polymerization proceeded in a well‐controlled manner to yield aromatic polyether‐block‐polyacrylonitrile (polyether‐b‐PAN) with low polydispersity. This block copolymer self‐assembled in N,N‐dimethylformamide to form bundle‐like or spherical aggregates, depending on the length of the PAN units in the block copolymer.magnified image

Reverse atom‐transfer radical polymerization of acrylonitrile catalyzed by FeCl3/iminodiacetic acid

AbstractFeCl3 coordinated by iminodiacetic acid (IMA) was Changed used for the first time as the catalyst in azobisisobutyronitrile‐initiated reverse atom‐transfer radical polymerization (ATRP) of acrylonitrile (AN). An FeCl3 to IMA ratio of 1:2 not only gave the best control of molecular weight and its distribution but also provided a rather rapid reaction rate. The effects of solvents on the polymerization of AN were also investigated. The rate of the polymerization in N,N‐dimethylformamide (DMF) was faster than in propylene carbonate or toluene. The molecular weight of polyacrylonitrile agreed reasonably well with the theoretical molecular weight in DMF. The rate of polymerization increased with increasing polymerization temperature and the apparent activation energy was calculated to be 54.8 kJ mol−1. The reverse ATRP of AN did not show obvious living characteristics with CuCl2 instead of FeCl3. Copyright © 2005 Society of Chemical Industry