@article{andrady_nunez_chiou_khan_2002, title={Rheology of concentrated solutions of hyperbranched polyesters}, volume={42}, ISSN={0032-3888 1548-2634}, url={http://dx.doi.org/10.1002/pen.11097}, DOI={10.1002/pen.11097}, abstractNote={Abstract}, number={11}, journal={Polymer Engineering & Science}, publisher={Wiley}, author={Andrady, Anthony L. and Nunez, Carlos M. and Chiou, Bor-Sen and Khan, Saad A.}, year={2002}, month={Nov}, pages={2065–2071} }
 @article{chiou_raghavan_khan_2001, title={Effect of colloidal fillers on the cross-linking of a UV-curable polymer: Gel point rheology and the Winter-Chambon criterion}, volume={34}, ISSN={["1520-5835"]}, DOI={10.1021/ma010281a}, abstractNote={The effect of colloidal silica fillers on the cross-linking behavior of a model UV-curable polymer system (thiol-ene) is studied using in situ rheology and real-time FTIR spectroscopy. The validity of the Winter-Chambon criterion (convergence of the loss tangents at the gel point) is examined for the cross-linking of these filled polymers, some of which are strongly flocculated dispersions (physical gels) prior to chemical cross-linking. Two different types of colloidal silica particles are studied: one with octyl chains tethered to the surface and the other with methyl surface groups. The Winter-Chambon criterion is satisfied for all samples containing the methyl-terminated silica. However, the criterion breaks down for samples containing the octyl-modified silica, with the loss tangents not converging at any single point. This suggests the absence of a self-similar critical gel at the gel point in the latter case. Neither type of silica particles alters the mechanism of the cross-linking reaction, as revealed by FTIR spectroscopy, but they do retard the cross-linking kinetics. An alternate method is suggested for determining the chemical gel point of filled systems that fail to obey the Winter-Chambon criterion. This method involves monitoring the critical strain (limit of the linear viscoelastic region) at various UV exposure times. A dramatic increase is observed in the critical strain at the gel point, indicating a transition from weak, physical bonds to strong, covalent cross-links.}, number={13}, journal={MACROMOLECULES}, author={Chiou, BS and Raghavan, SR and Khan, SK}, year={2001}, month={Jun}, pages={4526–4533} }
 @article{nunez_chiou_andrady_khan_2000, title={Solution Rheology of Hyperbranched Polyesters and Their Blends with Linear Polymers}, volume={33}, ISSN={0024-9297 1520-5835}, url={http://dx.doi.org/10.1021/ma991044z}, DOI={10.1021/ma991044z}, abstractNote={The rheological properties of different generations of hyperbranched polyesters in 1-methyl-2-pyrrolidinone solvent and their blends with a poly(2-hydroxyethyl methacrylate) are examined in this study. All the hyperbranched polyester solutions exhibit Newtonian behavior, with steady shear viscosities independent of shear rate. This indicates the absence of physical entanglements in these systems. In addition, solution viscosities are found to be only slightly affected by the different generations of the hyperbranched polymer. The polyesters have very small intrinsic viscosities, and their hydrodynamic radius scales as Rh ∼ M0.39, suggesting a less packed structure than dendrimers. All generations of the hyperbranched polyesters also show comparable apparent activation energies of flow over the temperature range studied. Replacing linear polymers with hyperbranched polymers causes large reductions in the blend viscosities. This behavior can be attributed to the decrease in both the number of physical entan...}, number={5}, journal={Macromolecules}, publisher={American Chemical Society (ACS)}, author={Nunez, Carlos M. and Chiou, Bor-Sen and Andrady, Anthony L. and Khan, Saad A.}, year={2000}, month={Mar}, pages={1720–1726} }