High molecular weight polyanilines and synthetic methods therefo

Details High molecular weight polyanilines and synthetic methods therefo High molecular weight polyanilines and synthetic methods therefo

1994-11-15

1996-05-21

Nagumo, Mark

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Nitrogen-containing reactant

525540, 252500, C08G 7300

Patent

active

055191118

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

This invention relates to polymers of aniline. More specifically, the invention relates to high molecular weight aniline polymers produced at relatively low reaction temperatures and at low concentrations of aniline species in solution. The invention also relates to articles fabricated from the inventive high molecular weight polymers.


BACKGROUND OF THE INVENTION

Much attention has recently been directed to polyaniline, due in large part to its excellent stability and the relatively high levels of electrical conductivity of certain of its structural forms. For example, one form of polyaniline known as "emeraldine base" or "polyaniline base" (structure (1), Y=0.5) can be protonated (doped) by dilute aqueous protonic acid such as hydrochloric acid to produce the corresponding salt (structure (2), A=Cl). This salt exhibits conductivities of about 1-5 Siemans per centimeter (S/cm) as a compressed powder pellet. ##STR1##
Polyaniline polymers can De processed into a variety of useful shaped articles such as fibers, films, and composites thereof. For many such applications, there is a positive correlation between increased molecular weight for the polyaniline employed and the performance properties of the resultant shaped article. Considerable attention has therefore been devoted to the development of polyanilines having high molecular weight. For example, M. Abe, et al., J. Chem. Soc., Chem. Commun., 1736-39 (1989), reported that polymerization of aniline at -3.degree. C. to -5.degree. C. produced polyaniline having a weight average molecular weight of 160,000 as measured by gel permeation chromatography (GPC) using a polystyrene standard and a 0.01 mol/dm.sup.3 LiBr/NMP solution as eluent. Abe, et al. observed that the molecular weight of polyaniline increases as its polymerization temperature decreases and hypothesized that the suppression of side reactions by lowering the polymerization temperature contributed to the increase in molecular weight.
Polyaniline polymers used to form shaped articles should have relatively low polydispersity, which is defined as the ratio of weight average molecular weight to number average molecular weight (i.e., M.sub.w /M.sub.n). As will be recognized, polydispersity, in conjunction with molecular weight, has a pronounced effect on properties such as melt viscosity, tensile strength, modulus, impact strength (toughness), and resistance to heat and corrosives. Lower polydispersity values generally indicate more controlled polymerization processes and higher quality polymers.
The solubility of the polyaniline is also an important processing consideration. Crosslinking a low molecular weight polyaniline to increase its molecular weight may render the polymer relatively insoluble in most known solvent systems and, hence, unusable from a manufacturing standpoint.
It would therefore be of great advantage to provide high molecular weight polyanilines of low polydispersity which are readily soluble in a variety of solvents.


OBJECTS OF THE INVENTION

Accordingly, it is one object of the present invention to provide high molecular weight polyanilines.
It is another object of the invention to provide high molecular weight polyanilines which can be efficiently elaborated into shaped articles.
It is yet another object of the invention to provide simple, reproducible methods for synthesizing high molecular weight polyanilines.
It is a further object to provide synthetic methods for producing polyaniline which involve polymerizing aniline at lower temperatures and at lower concentrations of aniline species in solution than those heretofore known in the art.
It is also an object of the invention to provide synthetic methods which involve polymerizing aniline in the presence of salts to provide high molecular weight polyaniline.


SUMMARY OF THE INVENTION

These and other objects are satisfied by the present invention, which provides high molecular weight polyanilines, along with preparative methods therefor. The methods generally comprise mixing aniline, protonic a

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