Recyclable Organocatalyzed Poly(Thiourethane) Covalent Adaptable Networks

Abstract

A new type of tetraphenylborate salts derived from highly basic and nucleophilic amines, namely 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), 1,8-diazabicyclo(5.4.0)undec-7-ene (DBU) and triazabicyclodecene (TBD), was applied to the preparation of networked poly(thiourethane)s (PTUs), which showed a vitrimer-like behavior, with higher stress-relaxation rates than PTUs prepared by using dibutyl thin dilaurate (DBTDL) as the catalyst. The use of these salts, which release the amines when heated, instead of the pure amines, allows the formulation to be easily manipulated to prepare any type of samples. The materials prepared from stoichiometric mixtures of hexamethylene diisocyanate (HDI), trithiol (S3) and with a 10% of molar excess of isocyanate or thiol were characterized by FTIR, thermomechanical analysis, thermogravimetry, stress-relaxation tests and tensile tests, thus obtaining a complete thermal and mechanical characterization of the materials. The recycled materials obtained by grinding the original PTUs and hot-pressing the small pieces in the optimized time and temperature conditions were fully characterized by mechanical, thermomechanical and FTIR studies. This allowed us to confirm their recyclability, without appreciable changes in the network structure and performance. From several observations, the dissociative interchange trans-thiocarbamoylation mechanism was evidenced as the main responsible of the topological rearrangements at high temperature, resulting in a vitrimeric-like behavior.

Actuator Behaviour of Tailored Poly(thiourethane) Shape Memory Thermosets

“…As we can see in Figure 4 , the degradation mechanism is quite complex, presenting three different stages. The first degradation step is attributed to the carbonyl sulphide elimination, as already demonstrated by Rogulska et al [ 43 ] and by our group, with a maximum placed around 300 °C [ 36 ]. This first peak is shifted to higher temperature when increasing the amount of HDI.…”

“…Trimethylolpropane tris(3-mercaptopropionate) (S3), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), 1-methylimidazole (1MI), and sodium tetraphenylborate (NaBPh 4 ) from Sigma-Aldrich (Saint Louis, MO, USA) were used as received. The base generator, 1-methylimidazolium tetraphenylborate (BG1MI) was synthesized according to a reported methodology [ 36 , 37 ]. Then, 10 mmol of 1MI were solubilized in 2.6 mL of H 2 O slightly acidified with 1 mL of conc., 36% HCl solution, and 11 mmol of NaBPh 4 were solubilized in water and stirred until complete homogenization.…”

“…We have synthetized a family of novel thermosets based on thiol-isocyanate “click” chemistry, in presence of a Lewis base, evaluating their performance as thermomechanical actuators. A thermal latent base (1-methylimidazolium tetraphenylborate) which releases 1MI at temperatures higher than 100 °C, previously developed by our group, has been selected as the catalyst [ 35 , 36 ]. The use of such latent base represents an interesting opportunity to reach temporal control of the reaction, offering the possibility to prepare the PTU thermosets in a controlled way; since the use of bases such as amines leads to a too quick thiol-isocyanate reaction, as already demonstrated in our previous paper [ 35 ].…”

Streamlined concept towards spatially resolved photoactivation of dynamic transesterification in vitrimeric polymers by applying thermally stable photolatent bases

“…study that thermally decomposes categorically under release of the free base catalyst. 10,19 By using the PLBs presented in this study, an undesirable thermally initiated onset of dynamic transesterification can be prevented at any temperature.…”

“…10 In addition, the pyridine served together with acetonitrile as a solvent, since quaternary ammonium salts containing tetraphenylborate are suffering from a low solubility in a wide variety of commonly used monomeric building blocks. 10,19 To avoid bubble formation at elevated temperatures in the fully cured material, pyridine and acetonitrile had to be gradually removed during curing by a lengthy vacuum treatment before the partially cured sample could be brought into its final shape. 10 In contrast to the non-basic borate salt, the photolatent tertiary amine of PLB-090 and PLB-1193 in its uncleaved initial, i.e.…”