In the present paper some main directions in mechanochemical synthesis are developed, based on the mechano‐destructive process induced under different conditions in homo‐ and heterochain solid polymers (polyethylene, cellulose and derivatives, polyesters and polyamides). The fact is known that the elastic energy conferred to crystalline amorphous polymers focuses on structural and composition defects distributed statistically, causing molecular ruptures of the homolytic type which generate nascent microcracks propagating and increasing within the solid leading finally to a fracture. The nascent microcrack represents in fact the existence within small volumes of a number of active macroradicals (or of a number of reactive functional groups after the stabilization of the destruction fragments) capable of reacting with appropriate chemical reagents existing in the working medium. On this basis became possible the initiation of graft polymerization, block copolymerization, polycondensation, and complexing reactions. The concentration of the elastic energy not on molecular underlayers but on metallic surfaces, even when these are the reaction vessel walls, leads to the formation of active centers of a particular type, capable of initiating homo‐ or copolymerization reactions.

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The application of mechanical energy on micro-and macromolecular solid bodies has as a result the formation of some new and energy-rich surfaces, strongly activated and able to develop reactions that are difficult to accomplish in other conditions. By vibratory milling of vinyl monomers in the presence of crystalline inorganic substances, grafted polymers are obtained which can be successfully used as filling materials in poly(viny1 chloride) processing. As a result of mechanical activation, the heterochain macromolecular compounds form new functional groups that are able to react with the judiciously selected micromolecular compounds by polycondensation reactions. This type of synthesis has also been extended to the carbochain polymers. By mechanodegradation, the latter ones form radicallic macromolecular fragments which can be stabilized with acceptors of the aromatic diamine type, leading to the obtainment of new polymers with special mechanical properties. The mechanochemical complexation was activated by vibratory milling, ultrasonic treatment, and cryolisis; the polyamides, cellulose, and polyesters were employed as macromolecular ligands; and the ions of Ti, V, Fe, Ni, and Mn were used as complexing centers. The vibratory milling of vinylic, acrylic, and dienic monomers, of the aromatic rings as well as of the nitriles, can activate their polymerization. The reaction takes place in the absence of any initiator, by a radical or ionic mechanism, as a function of the monomer chemical nature, the medium, and the gaseous atmosphere, respectively. The mechanochemically synthesized products are characterized by high thermostability , special 1025

Mechanical energy which is released by vibratory grinding is able to initiate polymerization reactions of some vinylic monomers. On this way it was possible to obtain poly(acrylonitrile) without any initiator or classical catalyst. The paper presents the physico‐chemical properties of the products obtained by vibratory grinding of acrylonitrile. For the characterization of the obtained polymers, IR‐, ESR‐, and Mössbauer‐spectra were used, together with X‐ray diffraction. Based on the chemical composition and spectral analysis a reaction mechanism and the polymer structure were proposed.

ABSTRACT:The paper shows evidence for the capacity of impact mechanical energy released by vibratory grinding to initiate polymerization reactions of acetonitrile. The influence of certain factors (reaction duration, gaseous atmosphere, medium polarity) was studied. The resultant products were characterised by spectral analyses; some specific properties determined by the presence of metallic atoms in the polymer chain are also evidence in support of this ability.KEY WORDS Acetonitrile I Poly(acetonitrile) I Mechanochemistry 1 Vibratory Grinding I Mechanochemical Polymerization I Recent studies 1 -3 have demonstrated the capacity of mechanical energy to activate vinyl monomers polymerization reactions without activation additives. This is evident in the synthesis of homo-and copolymers of acrylonitrile, styrene and vinyl acetate. The properties of the resultant polymers were found sometimes to differ from those of their homologues obtained by conventional methods.The presence of conjugated -C = N-double bonds 3 in the main chain of mechanochemically synthesised poly(acrylonitrile) led to the conclusion that the -C = N triple bond participates in the polymerization reaction.Several literature references show the possibility of polymerization of nitriles in the absence of initiators, at high temperatures and pressure (7-20 kbar), 4 to yield micromolecular triazinic products mixed with insoluble and infusible polymers resulting at high reaction rates. Solid state polymerization of nitriles was also possible by y-and X-rays irradiation. 5 • 6 Interesting results were obtained by the solid state polymerization of nitriles under high pressure and intense shear stress. 7 Under these conditions, homolytic breakage of some chemical bonds took place and free radicals, initiating the polymerization of -C = N group, resulted. 8 • 9 The synthesis of the polymers of some aromatic and aliphatic nitriles by ionic mechanism should also be mentioned. By using the complexes of metals belonging to II-IV and VIII groups for polymerization initiation, reaction products consisting of two fractions were obtained: an insoluble and infusible polymer in a significant amount and a soluble macromolecular compound in a lesser amount. 10 -13 The present paper deals with the polymerization of the -C = N triple bond by the action of mechanical energy, under vibratory grinding conditions. The influence of certain factors on this type of polymerization were studied and information on the reaction mechanism was obtained. EXPERIMENTALThe monomer was purified by distillation and drying on molecular sieves. The syntheses were performed on a vibratory mill (Labowi 191