Ring-opening metathesis polymerization of a diolefinic [2]-catenane-copper(i) complex:an easy route to polycatenanes

\u3cp\u3eA dilute (30 mM) dichloromethane solution of the copper(I) complex 1·Cu\u3csup\u3e+\u3c/sup\u3e of a [2]-catenane composed of two identical 28-membered macrocyclic alkenes featuring a phenanthroline moiety in the backbone was subjected to ring-opening metathesis polymerization (ROMP) with second-generation Grubbs catalyst. Shortly after mixing of reactants, the dark red solution transformed into a gel. The bis(phenanthroline)copper(I) units were effectively preserved during ROMP, as evinced by spectroscopic analysis. This implies that the putative metal alkylidene pseudorotaxane intermediates did not undergo dethreading processes but were involved in ring-chain equilibria strongly biased toward the ring products at the low monomer concentration employed in the ROMP reactions. MALDI-TOF mass spectra of the reaction mixtures obtained at an early stage of the reaction revealed a distribution of interlocked oligomers (1·Cu\u3csup\u3e+\u3c/sup\u3e)\u3csub\u3en\u3c/sub\u3e(PF\u3csub\u3e6\u3c/sub\u3e \u3csup\u3e-\u3c/sup\u3e)\u3csub\u3en-1\u3c/sub\u3e with n up to 7, with no traces of peaks ascribable to open chain species. Rheological and mechanical analyses of the gel products provided independent evidence in support of the conclusion that the fraction of linear species in the polymer is negligible. Indications were obtained that the major portion of the polymeric material is composed of fully interlocked species.\u3c/p\u3

Synthesis and self-assembly of discrete dimethylsiloxane-lactic acid diblock co-oligomers:The dononacontamer and its shorter homologues

\u3cp\u3eMost of the theoretical and computational descriptions of the phase behavior of block copolymers describe the chain ensembles of perfect and uniform polymers. In contrast, experimental studies on block copolymers always employ materials with disperse molecular makeup. Although most polymers are so-called monodisperse, they still have a molecular weight dispersity. Here, we describe the synthesis and properties of a series of discrete length diblock co-oligomers, based on oligo-dimethylsiloxane (oDMS) and oligo-lactic acid (oLA), diblock co-oligomers with highly noncompatible blocks. By utilizing an iterative synthetic protocol, co-oligomers with molar masses up to 6901 Da, ultralow molar mass dispersities (Đ ≤ 1.00002), and unique control over the co-oligomer composition are synthesized and characterized. This specific block co-oligomer required the development of a new divergent strategy for the oDMS structures by which both bis- and monosubstituted oDMS derivatives up to 59 Si-atoms became available. The incompatibility of the two blocks makes the final coupling more demanding the longer the blocks become. These optimized synthetic procedures granted access to multigram quantities of most of the block co-oligomers, useful to study the lower limits of block copolymer phase segregation in detail. Cylindrical, gyroid, and lamellar nanostructures, as revealed by DSC, SAXS, and AFM, were generated. The small oligomeric size of the block co-oligomers resulted in exceptionally small feature sizes (down to 3.4 nm) and long-range organization.\u3c/p\u3