Polythioamides of High Refractive Index by Direct Polymerization of Aliphatic Primary Diamines in the Presence of Elemental Sulfur

Abstract

Sulfur-containing polymers have renewed widespread attention due to their fascinating properties like high refractive index and semiconducting character. However, examples of direct polymerization involving elemental sulfur are limited. Herein, a new strategy to prepare polythioamide (PTA) by direct polymerization of aliphatic primary diamines in the presence of sulfur is reported. The polymerization of p-xylylenediamine (1) and sulfur at 110 °C in N-methyl-2-pyrrolidinone afforded PTA1 of high M w and high yield when the feed ratio of [1]:[S] ranged from 1:2 to 1:3. 1H NMR and 13C NMR spectra confirmed that there are three kinds of structural units among the PTA1 chains. Moreover, different diamines including m-xylylene­diamine (2), 1,6-hexane­diamine (3), ethylene­diamine (4), and 1,4-cyclohexane­diamine (5) were copolymerized with 1 in the presence of sulfur to obtain PTA copolymers. With an increase in 5 content, the copolymer PTA1/5 with an alternating sequence in the range of 56%–94% was prepared. Solubility and thermal properties of homopolymers and copolymers were studied. Meanwhile, the copolymers PTA1/3 and PTA1/5 possessed a high refractive index as high as 1.7.

Sulfur Chemistry in Polymer and Materials Science

“…Quite recently, a new strategy to prepare polythioamide derivatives with high molecular weight (37.900 < M w < 40.100 g·mol −1 ) and yield (up to 88.8%), respectively, from commercially available aliphatic primary diamines only in the presence of elemental sulfur was reported (Scheme E) . In similar manner to the previously reported MCP for the synthesis of polythioamides, this catalyst‐free methodology shows advantages including inexpensive and versatile monomers, tunable feed ratio, and atom‐economy.…”

Sulfur Radical Transfer and Coupling Reaction to Benzoxazine Groups: A New Reaction Route for Preparation of Polymeric Materials Using Elemental Sulfur as a Feedstock

“…Owing to the production of H 2 S(g) as a toxic byproduct, careful operation and safe reaction design for this process in laboratory and large‐scale operations are necessary. In laboratory work, dry nitrogen was passed through the reaction flask and a 0.1 m NaOH (aq) solution was bubbled through to absorb the H 2 S gas . Lead acetate paper was put in a glass tube connected to the gas stream to detect H 2 S.…”

“…In laboratory work, dry nitrogen was passed through the reaction flask and a 0.1 m NaOH (aq) solution was bubbled through to absorb the H 2 S gas. [32] Lead acetate paper was put in a glass tube connected to the gas stream to detect H 2 S.…”

Nucleophilic Activation of Elemental Sulfur for Inverse Vulcanization and Dynamic Covalent Polymerizations

“…Namely, we have incorporated these materials into high performance polymer cathodes for Li–S batteries, and used these novel CHIPs materials directly in lenses and windows for infrared thermal imaging and demonstrated their use as a new type of dynamic covalent polymeric materials . The impact of this work is also noted by the use of the inverse vulcanization technique by other research groups globally to prepare sulfur copolymers with a number of different organic comonomers including styrenics, alkynes, naturally occurring/commercial olefins, allylics, oleyamine, aliphatic amines, allyl ethers, maleimide, nitriles, and benzoxazines . While these initial advances point to the potential of this area, there remain synthetic challenges toward accessing a broader scope of functional CHIPs materials that would allow improvement of properties of these sulfur‐based materials.…”