Polyamide solution derived, preparation

The most important method used in the preparation of polyamides is direct amidation, usually through the intermediate formation of a salt of the diamine and dicarboxylic acid, but without it in the case of aminoacids or for pairs of monomers that do not readily form a salt. Esters can react with diamines to form polyamides with liberation of alcohol or phenol. Diamines can be reacted with diamides yielding polyamides and freeing ammonia. Polyamides have been prepared by acidolysis of acyl derivatives of diamines (compare Section 5.4 for acidolysis in polyester preparation). Bis-anhydrides react with diamines to form polyamides and, if reacted further, polyimides. The low-temperature reaction of acid chlorides with diamines has been used, interfacially or as a solution technique, to prepare certain polyamides (compare Section 5.7 for related reactions in polyester synthesis). 

Solution derived polyamides were prepared as 15% solids in N,N-dimethylacetaniide at room temperature under argon. The polyamides were isolated by slowly pouring the polymerization reaction mixtures into methanol and collecting the precipitated polymers. 

Quite recently,the anionic homopolymerization of a few substituted p-lactams and the copolymerization of some of the above pairs have been smdied in order to prepare polyamide 3-derived polypeptides displaying biological properties. The solution polymerization or copolymerization, initiated by li amide disubstituted with trrmethylsilyl groups and activated with 4-tert-butylbenzoyl chloride, does not have living character. From that study, some insights emerged into the reactivity of the above p-lactams in terms of their acidities, as well as electrophUidty of the imide end groups. 

Finally, polyamide films were prepared by spreading filtered solutions of the ODA based polymers in DMF, and the PDA-based polymers in DMAp/LiCl, onto a teflon coated surface. The films were dried at 60-125 T in a dust-firee chamber equipped with a nitrogen gas inlet. The films prepared with liCl were immersed in H2O to remove residual salts and DMAc. The films were light beige in color, and all were tough and flexible. The DMF prepared films were transparent and those derived from DMAp/LiQ were partially cloudy. Absence of residual solvent was demonstrated by TGA. 

As in the preparation of polyesters, also in the preparation of polyamides, the reaction temperature can be considerably reduced by using derivatives of dicarbo-xylic acids instead of the free acids. Especially advantageous in this connection are the dicarboxylic acid chlorides which react with diamines at room temperature by the Schotten-Baumann reaction this polycondensation can be carried out in solution as well as by a special procedure known as interfacial polycondensation (see Examples 4-11 and 4-12). 

Polyamides derived from D-glucose and D-glucosamine by interfacial and solution polycondensations of the sugar diamino derivatives with aromatic and aliphatic acyl chlorides have also been described [107]. The presence of an anomeric benzyl group did not decrease the reactivity of the 2-amino function. Similar chiral polyamides were synthesized from the 1,7-diamino derivative, which was prepared from D-glucal. 

Natural and synthetic rubber and synthetic resins are soluble in organic solvents resulting in cements, resin solutions, or lacquers. In addition, there are many cellulose derivatives, such as nitrocellulose, ethyl cellulose, and cellulose acetate butyrate, used in preparing solvent-based adhesives. Solvent-hased adhesives are also prepared from cyclized rubber, polyamide, and polyisobutylene. Low-molecular-weight polyurethane and epoxy compounds can be used with or without solvent. On the other hand, high-molecular-weight types or prepolymers require solvent to make application possible. 

Monomers derived from trimellitic anhydride, mainly V-carboxyphenyltrimel-litimides and V-(co-carboxyalkylene)trimellitimides have been also used many times as starting materials for the synthesis of poly (amide imide)s. These poly (amide imide)s have been traditionally prepared by low temperature solution polycondensation, from diamines and imide-diacid chlorides [182], but they have been also successfully synthesized by the phosphorylation method of direct polyamidation [184], from diamines and imide-diacids [185-188] as depicted in Scheme (36). Trimellitic acid imide (4-carboxyphthal-imide) has also been used for the preparation of poly(amide imide)s, by reaction with aliphatic and aromatic diamines in solution at moderate temperatures [189]. 

The polyamide obtained by polycondensation of 2,6-diaminopyridine and 2,6-pyridine dicarboxylic acid was the first polymer to assemble itself into a double helix (DNA-type) in solution. The synthesis and physicochemical characterization of some polymer-supported rhodium catalysts based on polyamides containing 2,6- and 2,5-pyridine units were reported by Michalska and Strzelec (2000) these catalysts were used for the hydrosilylation of vinyl compounds such as phenylacetylene. Chevallier et al. (2002) prepared polyamide-esters from 2,6-pyridine dicarboxylic acid and thanolamine derivatives and investigated their polymer sorption behavior towards heavy metal ions. Finally, Scorlanu et al. (2006) also prepared a polymer with improved performance based on polyureas containing 2,6-pyridine moiety and polyparabanic acids, and polymethane-ureas containing 2,6-pyridine rings. 

---