Association and Structure of Thermosensitive Comblike Block Copolymers in Aqueous Solutions

The structures and association properties of thermosensitive block copolymers of poly(methoxyoligo( ethylene glycol) norbornenyl esters) in D2O were investigated by small angle neutron scattering (SANS). Each block is a comblike polymer with a polynorbornene (PNB) backbone and oligo ethylene glycol (OEG) side chains (one side chain per NB repeat unit). The chemical formula of the block copolymer is (OEG3NB) 79- (OEG6.6NB) 67, where subscripts represent the degree of polymerization (DP) of OEG and NB in each block. The polymer concentration was fixed at 2.0 wt % and the structural changes were investigated over a temperature range between 25 and 68°C. It was found that at room temperature polymers associate to form micelles with a spherical core formed by the block (OEG3NB) 79 and corona formed by the block (OEG6.6NB) 67 and that the shape of the polymer in the corona could be described by the form factor of rigid cylinders. At elevated temperatures, the aggregation number increased and the micelles became more compact. At temperatures around the cloud point temperature (CPT) T ) 60 °C a correlation peak started to appear and became pronounced at 68 °C due to the formation of a partially ordered structure with a correlation length ∼349 Å.

Nebraska Agri-Business Association

When I was with you back in August of 2001, I mentioned that in New Mexico I served on the board of the New Mexico Agricultural-Chemical and Plant Food Association, and have, I hope, some appreciation of the work you do. I also truly appreciate your interest in your support of the work conducted at the Institute of Agriculture and Natural Resources at the University of Nebraska-Lincoln. Thank you for that! Your support, always critical, becomes even more so in such difficult, difficult economic times as our state finds itself in today. Nearly $4 million dollars was permanently slashed from the IANR budget in three rounds of budget cuts between October 2001 and August 2002, a result of Nebraska's continuing revenue shortfalls. At the same time, our frustrated IANR constituents make it clear that nearly $4 million of need did not disappear with our funding. Now more cuts are expected in this legislative session.