Cryochemical synthesis and structure of metal‐containing poly(p‐xylylenes): system poly(chloro‐p‐xylylene)‐Ag

Abstract

Polymer films with small Ag-clusters and Ag-nanocrystals were obtained by the cocondensation of Ag and chloro-p-xylylene from the gaseous phase followed by low-temperature solid-state polymerization. UV-Vis spectroscopic data show that the annealing of films at ambient temperature and thereafter at 373 K leads to a sharp rise of the amount of Agnanocrystals by aggregation of small clusters, but the mean size iof the nanocrystals remains practically constant. According to X-ray data, the lattice of Ag-nanocrystals is close to that of metallic Ag and i i s equal to approximately 50 A.

Metal‐Containing Polymers: Cryochemical Synthesis, Structure, and Physicochemical Properties

“…Cryochemical synthesis is based on low-temperature solid-state polymerization in conditions of frozen molecular mobility in the reacting system. Earlier it was shown that a number of monomers, such as acrylonitrile [18], formaldehyde [19][20][21], or p-xylylene (PX) and its derivatives [22][23][24], polymerize in solid state under g or UV radiation at 77 K and even close to the liquid helium temperature [18,20]. It is suggested that such polymerization is caused by specific supramolecular organization of solid-monomer-containing molecular aggregates, which are precursors of polymer chains [25].…”

“…In UV-Vis spectra of PPX films on a background of the PPX absorption, it is possible to observe only absorption bands of Ag n with n > 15, which, according to reference 9, should be in an "open" range of PPX spectrum at l > 320 nm. Because in this spectral range there are no absorption bands except for the absorption band of Ag nanocrystals, it may be concluded that clusters stabilized in obtained films contain less than 15 atoms [24,44].…”

“…The simultaneous vapor deposition of PX-, CN-PX-, and Cl-substituted PX (Cl-PX) with Ag at 77 K does not lead to complexation or the formation of any organometallic compounds [24,36,44]. In the case of PX and Cl-PX, such deposition proceeds without polymerization.…”

“…The co-deposition of CN-PX with Ag is accompanied by the partial polymerization of monomer. The initial condensates at 77 K contain a small amount of Ag nanocrystals that can be revealed and characterized using UV-Vis spectroscopy because such crystals have the specific absorption band of surface electron plasmons of about 430 nm Because D cr is proportional to the content of Ag nanocrystals and D 1/2 is in inverse proportion to their mean size (d¯) [3,47], one may conclude that the state and amount of Ag nanocrystals were not affected by the cryopolymerization [24,36,44]. Sharp growth of D cr at heating of obtained metal-polymer films specifies that the main part of Ag at 77 K is in a form of small noncrystalline Ag n clusters, which aggregate with formation of nanocrystals under the action of thermal relaxation processes in the polymer matrix.…”

“…However, in most cases metal does not interact chemically with a monomer, so that metal clusters and nanocrystals physically incorporated in polymer matrix are formed directly at vapor deposited cryochemical synthesis [4,24,43,44]. The primary products of cryochemical syntheses involving such metals or semiconductors are small atomic or molecular clusters.…”