High Melting Precision Sulfone Polyethylenes Synthesized by ADMET Chemistry

Abstract

A series of aliphatic polysulfones is synthesized via ADMET polymerization in which a sulfone group is located precisely after every 8th, 14th, and 20th carbon. Primary structural characterization is accomplished using 1H NMR, 13C NMR, and IR. Polymer morphology is studied by DSC and X‐ray scattering, which reveals layered morphologies comprised of polyethylene crystallites along with sulfone groups arranged in sheets. In contrast to other precision polymers with functional groups synthesized by ADMET, this morphology is found at all spacer lengths. Prior to hydrogenation the sulfone polymers show Tm decreasing with increasing sulfone concentration, a typical phenomenon attributed to the mix of cis and trans configurations producing defects in the crystals. However, following hydrogenation, the melting temperature increases as the sulfone group concentration increased rather than decreased, with the highest Tm being 175 °C. This is an increase of 45 °C relative to linear polyethylene synthesized via ADMET chemistry. The precise location of the sulfone groups, which are not tactic, within these polyethylenes increases crystallinity, promotes secondary bonding and increases Tm.

Synthesis of supramolecular precision polymers: Crystallization under conformational constraints

“…The unprotected DAP‐polymers ( 7a–c ) exhibit melting temperatures, that are above the T m of pure ADMET polyethylene ( T m = 134 °C), explainable by enhanced thermal stability due to hydrogen bonds, comparable to polymers bearing sulfone groups along the polyethylene backbone as demonstrated in literature . The observed cold crystallization apparent in every melting endotherm of the protected DAP polymers ( 6d–f and 7d–f ) can be interpreted as an at least partial incorporation of the functional group into the crystalline lamella, as the additional high supercooling (Δ T = 32–69 °C) implies a slower crystallization rate, similar to observations for other precision polymers .…”

“…Characteristic for all samples is a (001) reflection in the range 2.4 < q < 2.8 nm −1 , corresponding to lattice planes indicating the distance between two DAP‐units along the chain. The presence of a higher order reflection (002) at 4.8 < q < 5.6 nm −1 indicates a lamellar morphology, also observed for precision sulfone polyethylenes . The (001) reflection as well as the second order peak (002) shifts systematically to higher q values (corresponding to lower distances according to Bragg's law d hkl = 2 π / q hkl ) with decreasing methylene spacer length.…”

“…The successful conversion can be proven by the occurrence of the olefinic signals in the 1 H and 13 C NMR spectra in the range of 5.31–5.38 ppm and 130 ppm, respectively (see Supporting Information Figs. S15–S18), which can be assigned to the newly developed internal double bonds …”

“…In case of linear polymers, where long methylene sequences alternate with functional groups (“defects”) within the polymer backbone, their incorporation or exclusion into crystalline regions has been intensively studied . Especially precision polymers, resulting from acyclic diene metathesis (ADMET) polymerization or “click”‐based oligomerization chemistries, have been investigated in this context, often observing a layered arrangement of defects if the included moieties interact with each other via ionic‐forces or π–π‐stacking as observed for polymers bearing triazol‐rings, sulfonic, or amino acid groups in the main chain . Investigation of these inclusion‐ or separation effects has been accomplished using long chain alkanes and their derivatives as well as various periodic copolymers differing in branch identity and frequency.…”

Precision polymers containing main-chain-amino acids: ADMET polymerization and crystallization

“…[10][11][12][13][14][15] Acyclic diene metathesis polymerization (ADMET) 16 has been proven to be an excellent tool to achieve a polyethylene (PE)-like chain with functional monomers at precise locations. 17,18 Size, chemical structure and the steric structure of such "defects" to a large extent determine the nal crystallization behaviour in the solid state: when the precisely placed chemical elements are small (such as methyl 19,20 -, ethyl 21 -or halogen [22][23][24][25][26] -groups) they can be incorporated into the crystalline region of a semicrystalline polymer, whereas larger defects (higher alkyl substituents, 19,27 phosphoesters 28,29 or triazol-rings 30 and sulfonic-moieties 31 ) are excluded from the nal crystal-lattice.…”