Parylene N

Description

[2.2]Paracyclophane is used as an intermediate in organic synthesis or as a reagent in chemical reactions. It serves as the structural backbone of 4-toluenesulfinyl [2.2]p-dicyclohexane and can be used in the synthesis of various mono- and disubstituted [2.2]p-dicyclohexane derivatives. It can also be used for the preparation of metal complexes, and the interaction of the Ag+ cation with the cation -π of [2.2]paracyclophane can be used to synthesise Ag+ - [2.2]paracyclophane complexes using the Ag+ cation. The complex is formed by binding the cation Ag+ to three carbon atoms on a benzene ring of the [2.2]paracyclophane ligand using a cation-π interaction^[1].

Chemical Properties

Parylene N appears as white to light beige crystals or crystalline powder. It serves as an excellent dielectric material, characterized by a very low dissipation factor, high dielectric strength, and a frequency-independent dielectric constant. Parylene N does not contain any chlorine and is very crystalline. Parylene D contains two chlorine atoms per repeating unit. Parylene HT contains two fluorine atoms per repeating unit.

Characteristics

Parylene N has excellent electronic properties, including low dissipation factor, high dielectric strength, and low dielectric constant. These properties are beneficial for applications involving printed circuit boards and signal transmission. The extra chlorine in Parylene D results in slightly higher operating temperature for Parylene D relative to Parylene C.

Uses

2,2]-Paracyclophane is the raw material for the synthesis of parylene which is widely used in microelectronic integrated circuit.

Application

Parylene N, also known as [2.2]Paracyclophane, is a poly-p-xylene variant. Polyparacyclophane has been widely used as a coating for medical devices. It has also been used to make films and porous membranes on which cells can grow.Exposure of Parylene N films to UV light under aerobic conditions leads to the formation of aldehyde and carboxylic acid groups near the film surface. At the maximum exposure dose, the oxygen concentration on the surface of the Parylene N film is approximately 13% and decreases exponentially with depth. This suggests that further modelling and optimisation of this process could be used to regulate the surface concentration of oxygenated substances in poly(parylene) to optimise adhesion and wettability, or for chemical binding to other groups.^[2]

Synthesis Reference(s)

The Journal of Organic Chemistry, 46, p. 1043, 1981 DOI: 10.1021/jo00318a047

Flammability and Explosibility

Not classified

Synthesis

In a 1L three-necked flask, 45g of potassium carbonate, 58g of potassium fluoride and 1.2g of benzyltriethylammonium chloride were added and dissolved in 500mL of water. A solution of 61.8g of (2-chloro-4-chloromethylbenzyl)trimethylsilane dissolved in 100 mL of toluene was added and heated with vigorous stirring to a reaction of 80-85C for 3 h. The reaction was cooled, and the organic phase was separated by adding 300 mL of water to dilute it. The aqueous layer was then extracted with 300 mL of toluene. Combine the organic phases and concentrate, the crude product was recrystallized with 100mL of ethanol to obtain a total of 32g of white powder C-type dimer p-xylene, yield 88%.

In a three-necked flask, 48g of sodium hydroxide, 168g of sodium fluoride, 2.3g of benzyltriethylammonium chloride were added and dissolved in 800mL of water, and then 213g of (p-chloromethylbenzyl)trimethylsilane and 1000mL of toluene were added. The reaction was heated to 80 C with vigorous stirring for 2 h. The reaction was cooled and separated. The aqueous phase was extracted with toluene. Concentration, the crude product was recrystallized from ethanol to obtain 96g of white powder N-type dimer p-xylene, yield 92%

Purification Methods

Purify it by recrystallisation from AcOH. 1H-NMR : 1.62 (Ar-H) and -1.71 (CH2) [Waugh & Fessenden J Am Chem Soc 79 846 1957, IR and UV: Cram et al. J Am Chem Soc 76 6132 1954, Cram & Steinberg J Am Chem Soc 73 5691 1951. It complexes with unsaturated compounds: Cram & Bauer J Am Chem Soc 81 5971 1959, Syntheses: Brink Synthesis 807 1975, Givens et al. J Org Chem 44 16087 1979, Kaplan et al. Tetrahedron Lett 3665 1976]. [Beilstein 5 IV 2223.]

References

[1] DR. PETR VAURA; Dr. T U; Prof David Sykora. Interaction of the Silver(I) Cation with [2.2]Paracyclophane: Experimental and Theoretical Study[J]. ChemistrySelect, 2022. DOI:10.1002/slct.202203008.
[2] K. G. PRUDEN; S. B; K Sinclair. Characterization of parylene-N and parylene-C photooxidation[J]. Journal of Polymer Science Part A: Polymer Chemistry, 2003, 41 10: 1486-1496. DOI:10.1002/pola.10681.