Molecular modeling of structure-property relationship for palladium catalyzed poly(norbornene) and its derivatives

The unique properties of poly(norbornene) (PNB) and its derivatives have useful applications in the microelectronics industry as photoresist and dielectric materials. They also have potential for application to filtration membranes due to the large free volume elements they possess. Computer simulations have elucidated the origin of these rather unique properties of PNB and provided insight into how to optimize this material for various applications. Simulations of these polymers indicated they adopt a helical conformation that is occasionally disrupted by a kink that forms when the symmetry of the helix reverses. Because these kinks are rare in small chains but become more prevalent in larger chains the conformation of PNB transitions from rod-like to coil-like as the molecular weight is increased. Computer simulations that accurately reproduce the dimensions and wide angle x-ray diffraction patterns for PNB derivatives indicated that this helix-kink morphology is responsible for the unique properties of this polymer. These simulations have explained why free volume and coefficient of thermal expansion change with side groups. They have also explained the non-intuitive trend whereby the dissolution rate of PNB photoresists increase with increasing molecular weight.