Mukesh C. Bheda

STRUCTURE-PROPERTY RELATIONSHIPS IN SEGMENTED POLYVIOLOGEN IONENE ROTAXANES

Abstract The first structure-property relationships are reported for segmented polyrotaxane ionenes which possess the rotaxane moiety at the hard segment. These ionenes are based on PTMO/MDI (PTMO M n of 650, 1000, or 2000 daltons) as the elastomeric segment and paraquat hard segments with either PF6 − or Br− as the counterion. GPC indicates that these ionenes have a highly variable architecture with respect to the placement of the ionene hard segment. SAXS also supports the notion of a randomly placed hard segment because the interionic domain d spacings are not predictable or consistent. SAXS also shows there are few “lone multiplets” in the PF6 − derivative whereas there are considerable numbers of isolated ion pairs in the Br− ion-exchanged ionenes. Tensile testing shows that the PTMO-1000 and PTMO-2000 materials are elastomeric with good properties, but the PTMO-650 ionene is not elastomeric with the ionic hard segment as a continuous phase. Dynamic mechanical tests also indicate that these segmented...

Synthesis and polymerization of a bulky styrenic monomer as an in-chain ‘knot’ for polyrotaxanes

Abstract p-[Tris(p-t-butylphenyl)methyl]phenoxymethylstyrene (10) was prepared as a mixture of meta and para isomers via Williamson ether synthesis from vinylbenzyl chloride. Monomer 10 polymerizes smoothly under free-radical conditions. Under anionic polymerization conditions, nucleophilic attack at the benzylic position displaces the substituted phenoxide ion; by using an excess of n-butyllithium, however, a polymer of complex structure, high molecular weight and polydispersity of 2.2 was formed. On the basis of its steric bulk and polymerizability, new monomer 10 is therefore a useful in-chain ‘knot’ or ‘stopper’ for polyrotaxane synthesis using free-radical techniques, but not via anionic methods.

The Polyrotaxane Architecture. A New Approach to Molecular Engineering

In principle there are many subclasses of polyrotaxanes, differing in the nature and location of the covalent and physical linkages: main chain (1, 2) and side chain (3, 4) systems. These systems may possess bulky end blocking groups to ensure thermodynamic stability as in la, 2a, 3a and 4a or they may rely on kinetic retardation of dethreading due to random coiling, etc. as in lb, 2b, 3b and 4b. Homorotaxanes are comprised of cyclic and linear species which are chemically equivalent. Heterorotaxanes, on the other hand, involve cyclic and linear species having different chemical structures.