Aniline block polymerization

Bilayer structures have been prepared and investigated with various spectroelectrochemical techniques [307, 486]. In the former report, surface resonance Raman spectroscopy showed typical vibrational features of the involved polymers [PANI and poly(o-phenylenediamine] as already discussed were observed. In the latter investigation, involving PANI/poly(5-chlorine,2-metho3 ani-line), it was concluded that the topmost layer of the polymerized substituted aniline blocks the electrochemical reduction of the inner layer of PANI. This was first deduced from the diminished height of reduction peaks in the CV. Moreover, this was supported by in situ UV-vis spectra that showed typictil bands of oxidized PANI even after formal reduction of the film. 

The basic building blocks for polyurethanes are polyisocyanates and macroglycols, also called polyols. The commonly used polyisocyanates are tolylene-diisocyanate (TDI), diphenyimethane diisocyanate or methylenediphenyl isocyanate (MDl), and polymeric methylenediphenyl isocyanate (PMDI) mixtures manufactured by phosgenating aromatic polyamines derived fi-om the acid-catalyzed condensation of aniline and formaldehyde. MDl and PMDI are produced by the same reaction, and separation of MDl is achieved by distillation. The synthetic routes in the manufacture of commercial polyisocyanates are summarized in Figme 4.28. 

Initiators with the blocked amino groups, such as p-ihio-NJ f-bis(trimethylsilyl)aniline, have been used for anionic polymerization (Fig. 7). 

As a specific example of the synthesis of polymers with the aniline oligomer building blocks, various polyureas (12) were prepared from the polymerization of the... 

Another widely used approach is the in situ polymerization of an intractable polymer such as polypyrrole onto a polymer matrix with some degree of processibil-ity. Bjorklund [30] reported the formation of polypyrrole on methylcellulose and studied the kinetics of the in situ polymerization. Likewise, Gregory et al. [31] reported that conductive fabrics can be prepared by the in situ polymerization of either pyrrole or aniline onto textile substrates. The fabrics obtained by this process maintain the mechanical properties of the substrate and have reasonable surface conductivities. In situ polymerization of acetylene within swollen matrices such as polyethylene, polybutadiene, block copolymers of styrene and diene, and ethylene-propylene-diene terpolymers have also been investigated [32,33]. For example, when a stretched polyacetylene-polybutadiene composite prepared by this approach was iodine-doped, it had a conductivity of around 575 S/cm and excellent environmental stability due to the encapsulation of the ICP [34]. Likewise, composites of polypyrrole and polythiophene prepared by in situ polymerization in matrices such as poly(vinyl chloride), poly(vinyl alcohol), poly(vinylidine chloride-( o-trifluoroethylene), and brominated poly(vi-nyl carbazole) have also been reported. The conductivity of these composites can reach up to 60 S/cm when they are doped with appropriate species [10]. 

The polymerization of S initiated by potassium amide in liquid ammonia yields polymers with one primary amine group per chain (Scheme 34)." Initiators with blocked amino groups such as p-lithio-N,iV-bis(trimethylsilyl)aniline (54) have been used to initiate anionic polymerizations. Difunctionality was then achieved by coupling two growing chains with dimethyldichlorosilane, and deprotecting the primary amine end groups by acid hydrolysis. 

To prepare model compounds representing the polymers structures two model compounds were prepared by reacting imidazole-blocked phenyl isocyanate (T STC) with PMDA and BPDA (coded PMDA-M and BPDA-M, respectively) under the same conditions as polymerization reaction. However, from the same reaction with NTDA we could not obtain pure compound NTDA-M and the yield was low(27 %). Tlie product obtained always revealed some incomplete cyclization, and it needed be additionally cyclized by reflux in acetic anhydj ide for prolonged time. More conveniently and in higher yield, it could be prepared by direct condensation with aniline in cyclohexane/DMAc mixture at reflux temperature. 

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