The mechanism of polymerization of p-xylylene and its derivatives is analyzed at the theoretical level. The polymerization reaction takes place in vacuo without any catalyst. The first step is a pyrolytic decomposition of starting material for polymerization, p-cyclophane, a cyclic dimer of p-xylylene, into biradical linear dimer and finally into two quinonoid monomeric molecules of p-xylylene. The quinonoid monomer is diamagnetic; i.e., it has a singlet ground state. The monomers after pyrolysis, when the temperature is lowered, do not re-form cyclic dimers but instead polymerize into long chain molecules. The initiation of polymerization requires dimerization of two monomers leading to formation of a genuine noncoupled biradical dimer. The chain molecules grow through the propagation reaction only one unit at a time, by the attachment of a monomer to a radical chain end. In this work the pyrolysis reaction, the initiation reaction and the first propagation steps of parylene polymerization (up to pentamer) are studied in details using different quantum chemical methods: AM1 and PM6 semiempirical methods and density functional theory (DFT) approach using B3LYP functional with two basis sets of different size (SVP and TZVP).

In this work we used a combination of classical molecular dynamics and simulated annealing techniques to shed more light on the conformational flexibility of 12 adenosine triphosphate (ATP) analogues in a water environment. We present simulations in AMBER force field for ATP and 12 published analogues [Shah et al. (1997) Proc Natl Acad Sci USA 94: 3565–3570]. The calculations were carried out using the generalized Born (GB) solvation model in the presence of the cation Mg2+. The ion was placed at a close distance (2 Å) from the charged oxygen atoms of the beta and gamma phosphate groups of the −3 negatively charged ATP analogue molecules. Analysis of the results revealed the distribution of inter-proton distances H8–H1′ and H8–H2′ versus the torsion angle ψ (C4–N9-C1′–O4′) for all conformations of ATP analogues. There are two gaps in the distribution of torsion angle ψ values: the first is between −30 and 30 degrees and is described by cis-conformation; and the second is between 90 and 175 degrees, which mostly covers a region of anti conformation. Our results compare favorably with results obtained in experimental assays [Jiang and Mao (2002) Polyhedron 21:435–438].FigureDihedral O4′–C1′–N9–C4 angle dependence on inter-proton distances H8–H1′ (crosses) and H8–H2′ (dots) measured for ATPElectronic supplementary materialThe online version of this article (doi:10.1007/s00894-010-0808-3) contains supplementary material, which is available to authorized users.

Parylene C, poly(chloro-para-xylylene) is the most widely used member of the parylene family due to its excellent chemical and physical properties. In this work we analyzed the formation of the parylene C film using molecular mechanics and molecular dynamics methods. A five unit chain is necessary to create a stable hydrophobic cluster and to adhere to a covered surface. Two scenarios were deemed to take place. The obtained results are consistent with a polymer film scaling growth mechanism and contribute to the description of the dynamic growth of the parylene C polymer.Electronic supplementary materialThe online version of this article (doi:10.1007/s00894-011-1050-3) contains supplementary material, which is available to authorized users.

The p-xylylene monomers of parylene N, C and D have similar high polymerization reactivity. For effective copolymerization processes this fact is basically a drawback and for instance the copolymerization with styrene doesn’t go at all (Corley et al. J Pol Sc 13(68):137–156, [15]). Substitution of terminal hydrogen atoms by chlorine atoms reduces reactivity dramatically. 7,7,8,8-tetrachloro-p-xylylene and 2,5,7,7,8,8-hexachloro-p-xylylene can be isolated as yellow crystals. These crystals can be kept without any change in temperature below 0 ∘C, but they polymerize slowly at room temperature. Perchloro-p-xylylene is stable even at elevated temperatures and does not polymerize under any conditions. Both 7,7,8,8-tetrachloro-p-xylylene and 2,5,7,7,8,8-hexachloro-p-xylylene copolymerize with various vinyl monomers, such as styrene and others. In this work the polymerization reactions of different chloro-derivatives of p-xylylene were modeled by means of the DFT method with hybrid correlation functionals (B3LYP and PBE0) and, for comparison, by means of the Hartree Fock methods. We inquired both initiation as well as elongation polymeric reactions for each of the reactants. We survied their reactivity analytically examining energetics and configurations in Szwarc-like process. The quantitative influence of chlorine atoms on the reactivity in polymerization steps, their location in the reactants’ structure (aromatic and/or aliphatic) as well as their number, were reviewed. The polymerizations of p-xylylenes with chlorine atoms as terminal aliphatic substituents yet revealed one more access path for parylenes’ in situ functionalization.Electronic supplementary materialThe online version of this article (doi:10.1007/s00894-016-3179-6) contains supplementary material, which is available to authorized users.