Synthesis and Crystallization of Precision Polymers with Repetitive Folding Elements

Abstract

The synthesis and thermal properties of a new type of precision polyethylene containing perfectly placed conformationally constraining elements after every 16 methylene units are presented. The precise placement of a 2,6-diaminopyridine moiety (DAP) is accomplished via acyclic diene metathesis (ADMET) polymerization of specially designed monomers, where the DAP serves as the conformational constraint. Polymerization of the diene-mono mer ( N,N′ -pyridin-2,6-diyl-bis-dec-9-enamide) displaying free-amide hydrogen bonds leads to largely insoluble polymers due to self-aggregation via the hydrogen bonds and π-π stacking. However, when using the N -methyl-protected monomer N,N ′-pyridin-2,6-diylbis( Nmethyldec-9-enamide), the polymerization furnishes soluble polymers with molecular weights ranging from 1500 up to 60 000 g mol −1 using different Grubbs or Umicore catalysts. Matrix-assisted laser desorption/ionization (MALDI) measurements prove the structure of linear and cyclic polymers, all containing the precisely placed DAP units within the polymer. Subsequent hydrogenation with p -toluenesulfonhydrazide yields the fi nal semicrystalline polymers, displaying an ordered lamellar crystal phase as characterized via differential scanning calorimetry (DSC) and X-ray diffraction (XRD) measurements.

Hybrid polymers bearing oligo-l-lysine(carboxybenzyl)s: synthesis and investigations of secondary structure

“…Our synthetic strategy is based on a combination of ring opening polymerization (ROP) of N-carboxyanhydride (NCA), followed by ADMET polymerization of appropriately bis-enefunctionalized oligomers to place the folding-elements of Lys n s along a polymer chain, subsequently studying their intraand interchain secondary structures. Acyclic diene metathesis (ADMET) polymerization [32][33][34] opens up possibilities to introduce different kinds of functional groups [35][36][37][38] into a polyethylene chain, introducing even anti-inammatory drugs, such as ibuprofen and naproxen, into a polyethylene backbone. 39 The ROP of NCA monomers is a viable and proven strategy to obtain articial homo-and block co-peptides, where end group functionalized polymers can be obtained, given that the ROP mechanism follows the aspects of "livingness".…”

Synthesis of supramolecular precision polymers: Crystallization under conformational constraints

“…The required monomers 1a–c , 2a–f , and 5 bearing a DAP unit were synthesized as mentioned previously in a Schotten–Baumann reaction using DCM and water as solvent and NaOH as base, whereby acid chlorides with different alkyl chain lengths ( x = 7, 8, 9) and DAP were chosen as precursors. Subsequently, the free amide groups were protected by the reaction of the unprotected monomers 1a–c with either methyl iodide or benzyl bromide to sustain the solubility of the compounds after polymerization (see Scheme ).…”

“…The hydrogenation of the polymers was achieved by the reaction with TsNHNH 2 and N,N ‐diisopropylethylamine in DMF at 150 °C for 6h, which already turned out to be a successful method, proving the completeness to the fully saturated polymers ( 7d–i ) by the disappearance of all olefinic signals (from 4.90 to 5.84 ppm) and the formation of terminal methyl groups (0.85–0.88 ppm) in the 1 H NMR spectra (see Supporting Information Fig. S20).…”

“…All DAP monomers were synthesized in a biphasic Schotten–Baumann reaction according to our previous investigations . A one‐necked flask was filled with 2,6‐diaminopyridine (1 eq.)…”

“…The protection of the amides ( 1a–c ) with methyl and benzyl protection groups was carried out as reported previously . A two‐necked flask was filled with a solution of the unprotected monomer 1a–c (1 eq.)…”