spopsisThe interaction between sodium poly(styrene sulfonate) (NaSS) and side-chain charged polycation polymer (pendent type) or main-chain charged polycation polymer (integral type) has been studied. It was found that the polyion complex (the reaction product of these polyelectrolytes) of pendentrpendent type has an equimolar composition a t any mixing ratio of two component polymers. However, a polyion complex of integral-pendent type can form a water-soluble complex with a ratio of [polycation] / [polyanion] =The mechanism of formation of this specific complex is discussed.in addition to a complex with a equimolar composition.
Polyaniline and polypyrrole are the most widely studied conducting polymers and are often synthesized by a simple oxidative polymerization method in a bulk solution. The resulting polymers show either granular or fibrillar morphology, depending on experimental conditions. 1-3 Some groups have also reported that spherical polymers are formed by using steric stabilizers 4-6 or by synthesizing polymers by microemulsion process. 7,8 In addition, inorganic and organic materials 9 like silica, salicylic acid, 10 and -naphthalene sulfonic acid 11 are employed for preparing polyaniline particles of different shapes. Microspheres comprising conducting polymers may probably be well suited for certain specific applications such as conducting paints and antistatic agents. They have been also applied to conducting fillers in transparent conducting thin films.12 In particular, microspheres having a smooth surface are expected to form easily two-or three-dimensional periodic lattices possessing photonic band gap, which will lead to novel optical properties. 13,14 However, a fine tuning of the morphology and the size of conducting polymer spheres still needs some improvement.Up to the present time, several reports have described morphological studies of polyaniline and its ring substituted derivatives generated by electrochemical means. The synthesized polymer films showed either fibrillar or granular morphology just like those formed in solutions. 15,16 We have recently reported the formation of microspheres based on electrochemical oxidation of N-methylaniline (NMA) in acid solutions, although the resulting poly(N-methylaniline) (PNMA) microspheres were fused in part to the electrode surface and were hard to be isolated. 17,18 However, this self-assembling nature of NMA to form spherical particles hints us the possibility for the formation of PNMA microspheres by chemical oxidation of NMA in a solution.The present communication describes a templatefree formation of PNMA microspheres based on a simple chemical polymerization method using monomer, acid, and oxidant. EXPERIMENTAL N-Methylaniline (NMA), aniline, o-toluidine and o-anisidine used as monomer were distilled under reduced pressure. Adipic acid, HClO 4 , HBF 4 , H 2 SO 4 , HCl, HNO 3 , (NH 4 ) 2 S 2 O 8 (APS), FeCl 3 , and K 2 Cr 2 O 7 were used as received. Appropriate quantities of monomer and acid were dissolved in deionized water. An oxidant solution was added to the solution and the reaction was maintained for a given period of time until adding an excess amount of ethanol to the solution for stopping the polymerization. The resulting solution was centrifuged, and the precipitate was washed repeatedly with water and alcohol several times. Finally, the product was dried in vacuum for 24 h at room temperature.The morphology and size of PNMA microspheres were measured with a JEOL JSM-6320F field-emission scanning electron microscope (SEM). A 20 nm Pt layer was sputtered on the sample prior to SEM measurements.RESULTS AND DISCUSSION
ABSTRACT:Microspheres of conducting poly(N-methylaniline) were obtained by a potential-sweep polymerization of N-methylaniline in 1 M HClO 4 solution. The average diameter of the microspheres grown from 0.8 M monomer concentration by sweeping potential at 50 mV s À1 for 12 cycles was 1.9 mm. The size of microspheres could be controlled by changing several experimental parameters including scan rate, monomer concentration and cycle number. Among different acids used for polymerization process, only HClO 4 and HBF 4 showed ability of microspheres formation. The increase in size of alkyl group at N-position of aniline ring tended to inhibit the growth of microspheres. The formation of microspheres probably occurs through oligomer-coupled polymerization process.
Monodisperse and isolated microspheres of poly(N-methylaniline) were successfully prepared through chemical polymerization of N-methylaniline by S 2 O 8 2in adipic acid containing poly(vinylpyrrolidone) (PVP). Mean diameters of the microspheres with smooth surfaces changed from 320 to 100 nm by increasing the reaction temperature from 25 to 75 o C. The concentration of PVP did not affect much the size of microspheres, but the increased PVP concentration led to longer induction times for the onset of dispersion polymerization.
When p‐xylylenedichloride (XDC) and α.ω‐tert‐diamines are present in equimolar amounts in dimethylformamide (DMF), fairly fast polymerization occurs to form the polycation polymers of integral type owing to the structural characteristic of XDC to stabilize the transition state with delocalization. The reactivities based on the structures of monomers are as follows: Diamines: Dihalogren compounds: The reactivity of XDC is remarkable. The reaction of TED and XDC proceeds by nucleophilic bimolecular substitution (SN2), thus the rate Eq. is, v = k · [XDC][TED]. The fact that this polymerization is considerably faster than the normal MENSCHUTKIN reaction may be attributed to the structure of XDC above mentioned and the solvent effect of DMF that solvates cations only. The activation energy and log of the frequency factor of this polymerization are 9.6 and 5.61 kcal/mole, respectively.
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