Controlled Cationic Ring-Opening Polymerization of 1,3-Oxazolidine-2-thione Derived from l-Serine

Abstract

The cationic ring-opening polymerization of a 1,3-oxazolidine-2-thione derivative (SL) from L-serine was examined. SL was synthesized by the reaction of L-serine methyl ester hydrochloride with carbon disulfide and hydrogen peroxide in the presence of triethylamine. Cationic polymerizations using methyl trifluoromethanesulfonate (TfOMe), trifluoromethanesulfonic acid (TfOH), and boron trifluoride etherate (BF3‚OEt2) as initiators gave polymers with polythiourethane structures in quantitative yields. The obtained polymers showed inverted specific rotations with respect to the monomer, where the large increase of the absolute values suggested the possibility of high-order structures. The molecular weight of the polymer was controlled by the feed ratio of SL to TfOMe and its distribution was constantly narrow (Mw/Mn < 1.14), supporting the controlled character of the polymerization. The reaction mechanism was examined for TfOMe. According to NMR spectroscopic experiments, the polymerization with TfOMe proceeds via an active chain end mechanism in which the protonated cyclic endo iminothiocarbonate 2 is the active species. The propagation step involves a nucleophilic attack of SL to the active species.

Development of High Refractive Index Plastics

“…At present, PTUs are being experimented for various uses such as lenses, prisms, optical fibers, optical filters, information recording medium and light emitting diode [26][27][28][29][30][31][32][33]. Polysulphones have a high refractive index of 1.634 -1.675 and are desirable for many lens applications as they can be easily cast into thin lenses.…”

“…Sulfur containing monomers are good candidates for producing high refractive index optical materials; ready polarizability of a sulfur produces a strong interaction between the material and incident light, resulting in high refractive index [55]. Sulfur containing polymers including polythiourethanes are therefore, nowadays, being developed as optical materials because of their high refractive index [26][27][28][29][30][31][32][33].…”

“…The polythiourethanes have a high refractive index, low dispersion of refractive index and they are light weight, colorless and transparent [26][27][28][29][30][31][32][33]80]. Aliphatic or alicyclic polyisoyanates have been used alongwith thiol compounds to prepare high refractive index optical plastics having a refractive index greater than 1.60.…”

A Convenient Synthesis of Amino Acid Methyl Esters

“…Amino acid methyl esters are important intermediates in organic synthesis, which have been used in various areas such as peptide synthesis [1], medicinal chemistry [2,3], as chiral sources [4,5,6,7] and polymer materials [8,9]. …”

Characterization, structural transitions and properties of a tightly crosslinked polythiourethane network for optical applications

“…Several methods are suitable to synthesize polythiourethanes. Chain polymerization, especially cationic ring-opening polymerization of cyclic thiourethane compounds [5][6][7], provides polythiourethanes with highly organized macromolecular structures and controlled architectures. Polyaddition reactions of polythiols with polyisocyanates yield A 2 B 2 thermoplastics [8] or A f B g (f, g, or both > 2) thermosetting polymers.…”