@misc{gurarslan_tonelli_2017, title={Do we need to know and can we determine the complete macrostructures of synthetic polymers?}, volume={65}, ISSN={["1873-1619"]}, DOI={10.1016/j.progpolymsci.2016.09.001}, abstractNote={The complete molecular architectures of synthetic polymers, which may be called their macrostructures, consist of the types and amounts of short-range microstructural elements they contain, such as comonomer, regio- and stereosequences, branches, cross-links etc., as well as their locations along the polymer backbone. While spectroscopic probes that are only sensitive to local polymer structures, like NMR, can identify and quantify short-range microstructural elements, they are unable to locate their positions along the polymer backbone. Consequently, the present situation regarding our ability to characterize the complete chemical structures of synthetic polymers would be analogous to that of proteins if it were only possible to determine their amino acid compositions or possibly the amounts of consecutive pairs or even triplets of constituent amino acids, rather than their complete macrostructures, i.e., their complete amino acid sequences or primary structures. While the genetic DNA code may be read to determine the primary structures of most proteins, we have no such synthetic template for man-made polymers which can be utilized to determine their complete macrostructural architectures. Just as the primary sequences of proteins determine their secondary, tertiary, and even quaternary structures, and of course their resultant biological functions, it can logically be presumed that the behaviors of synthetic polymers are also principally the result of their complete structural architectures. Though important, the types and quantities of short-range microstructures polymers contain and which constitutes our present level of structural knowledge, is insufficient for the development of truly relevant structure-property relations. In addition, the degree of macrostructural heterogeneity among the chains in polymer samples is also expected to strongly influence the behaviors of materials made from them, and so this related issue also needs to be addressed. Here we summarize our recent attempts to develop and demonstrate an experimental approach that can be used to begin to characterize the complete macrostructures of synthetic polymers and to illustrate the relevance of this knowledge to understanding their properties and behaviors.}, journal={PROGRESS IN POLYMER SCIENCE}, author={Gurarslan, Rana and Tonelli, Alan E.}, year={2017}, month={Feb}, pages={42–52} }
 @article{gurarslan_tonelli_2016, title={An unexpected stereochemical bias in the RAFT syntheses of styrene/p-bromostyrene copolymers uncovered by the Kerr effect}, volume={89}, ISSN={["1873-2291"]}, DOI={10.1016/j.polymer.2016.02.032}, abstractNote={During our recent investigations of the viability of using the observed contributions synthetic polymers make to the birefringence of their dilute solutions when subjected to strong electric fields, i.e., their Kerr effects, to characterize the complete architectures or macrostructures of their chains, we discovered a surprising result. The Kerr constants measured for styrene/p-bromostyrene (S/pBrS) copolymers synthesized by controlled RAFT copolymerization could only be reproduced by their predicted calculated values when we assumed that pBrS─pBrS diads were enchained with a strong preference for the racemic (r) stereosequence, while at the same time S─S diads show no such stereochemical preference. Gradient and random S/pBrS copolymers made by RAFT showed similar Kerr constants, while those made by FRP and ATRP had Kerr effects different by a factor of two or more and were similar to those shown by samples with resultant blocky and random comonomer sequences made previously by BR of a-PS in poor and good solvents, respectively. By comparison to the Kerr effects observed for S/pBrS copolymers with similar compositions and comonomer sequences, but obtained by bromination (BR) of atactic polystyrene (a-PS) or uncontrolled free-radical (FRP) and controlled ATRP syntheses, which are well known to produce random atactic vinyl homo- and copolymers, we were able to confirm the stereochemical bias introduced during our controlled RAFT copolymerizations first suggested by our Kerr effect observations. Our Kerr effect observations and the conclusions drawn from them received further confirmation from the dewetting behaviors of their thin films observed from silicon wafers when they were heated well above their Tgs. For example, thin atactic S/pBrS films made by uncontrolled FRP and controlled ATRP free-radical polymerizations with random commoner sequences dewetted rapidly from silicon wafers when heated, while thin films made from atactic S/pBrS with random comonomer sequences, but obtained by controlled RAFT syntheses were “stickier”, and only dewet from silicon wafers after much longer annealing times. We suggest this increased “stickiness” of the RAFT synthesized S/pBrS copolymers is attributable to pBrS─pBrS diads with predominantly racemic structures that adopt preferred trans─trans conformations. In trans─trans racemic pBrS─pBrS diads, neighboring side chains are placed on opposite sides of the copolymer backbone in position for their p-Brs to strongly interact with the silicon wafer surfaces.}, journal={POLYMER}, author={Gurarslan, Rana and Tonelli, Alan E.}, year={2016}, month={Apr}, pages={50–54} }
 @article{gurarslan_hardrict_roy_galvin_hill_gracz_sumerlin_genzer_tonelli_2015, title={Beyond Microstructures: Using the Kerr Effect to Characterize the Macrostructures of Synthetic Polymers}, volume={53}, ISSN={["1099-0488"]}, DOI={10.1002/polb.23598}, abstractNote={ABSTRACT The macrostructures of synthetic polymers are essentially the complete molecular chain architectures, including the types and amounts of constituent short‐range microstructures, such as the regio‐ and stereosequences of the inserted monomers, the amounts and sequences of monomers found in co‐, ter‐, and tetra‐polymers, branching, inadvertent, and otherwise, etc. Currently, the best method for characterizing polymer microstructures uses high field, high resolution 13 C‐nuclear magnetic resonance (NMR) spectroscopy observed in solution. However, even 13 C‐NMR is incapable of determining the locations or positions of resident polymer microstructures, which are required to elucidate their complete macrostructures. The sequences of amino acid residues in proteins, or their primary structures, cannot be characterized by NMR or other short‐range spectroscopic methods, but only by decoding the DNA used in their syntheses or, if available, X‐ray analysis of their single crystals. Similarly, there are currently no experimental means to determine the sequences or locations of constituent microstructures along the chains of synthetic macromolecules. Thus, we are presently unable to determine their macrostructures. As protein tertiary and quaternary structures and their resulting ultimate functions are determined by their primary sequence of amino acids, so too are the behaviors and properties of synthetic polymers critically dependent on their macrostructures. We seek to raise the consciousness of both synthetic and physical polymer scientists and engineers to the importance of characterizing polymer macrostructures when attempting to develop structure–property relations. To help achieve this task, we suggest using the electrical birefringence or Kerr effects observed in their dilute solutions. The molar Kerr constants of polymer solutes contributing to the birefringence of their solutions, under the application of a strong electric field, are highly sensitive to both the types and locations of their constituent microstructures. As a consequence, we may begin to characterize the macrostructures of synthetic polymers by means of the Kerr effect. To simplify implementation of the Kerr effect to characterize polymer macrostructures, we suggest that NMR first be used to determine the types and amounts of constituent microstructures present. Subsequent comparison of observed Kerr effects with those predicted for different microstructural locations along the polymer chains can then be used to identify the most likely macrostructures. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53 , 155–166}, number={3}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, author={Gurarslan, Rana and Hardrict, Shauntrece and Roy, Debashish and Galvin, Casey and Hill, Megan R. and Gracz, Hanna and Sumerlin, Brent S. and Genzer, Jan and Tonelli, Alan}, year={2015}, month={Feb}, pages={155–166} }
 @article{gurarslan_gurarslan_tonelli_2015, title={Characterizing Polymers with Heterogeneous Micro- and Macrostructures}, volume={53}, ISSN={["1099-0488"]}, DOI={10.1002/polb.23645}, abstractNote={The potentially extreme heterogeneity of polymer micro- and macrostructures has been demonstrated and a means for characterizing them has been suggested. To ensure that all possible microstructures, such as diad stereosequences in vinyl homopolymers and monomer sequences in copolymers, including their locations along polymer chains, that is, all macrostructures, are represented, it became necessary to generate samples with huge quantities (many many tons) of constituent polymer chains. This suggested a practical need for distinguishing between polymer samples with chains that have homogeneous and heterogeneous populations of micro- and macrostructures. A combination of high resolution 13C-nuclear magnetic resonance to determine the types and amounts of constituent short-range microstructures, and dilute solution electrical birefringence or Kerr effect measurements to locate them along the polymer chains has been suggested, and may be able to achieve this distinction. This combination of techniques is required to reduce the innumerably large numbers of different possible polymer macrostructres whose Kerr constants would have to be calculated, for comparison to the observed values. The ability to determine polymer macrostructures is critical to the development of relevant, more meaningful, and therefore, improved structure–property relations for polymer materials. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 409–414}, number={6}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, author={Gurarslan, Rana and Gurarslan, Alper and Tonelli, Alan E.}, year={2015}, month={Mar}, pages={409–414} }
 @article{hardrict_gurarslan_galvin_gracz_roy_sumerlin_genzer_tonelli_2013, title={Characterizing polymer macrostructures by identifying and locating microstructures along their chains with the kerr effect}, volume={51}, ISSN={["0887-6266"]}, DOI={10.1002/polb.23248}, abstractNote={Abstract In this brief report, we demonstrate that Kerr effect measurements, which determine the excess birefringence contributed by polymer solutes in dilute solutions observed under a strong electric field, are highly sensitive to and capable of determining their microstructures, as well as their locations along the macromolecular backbone. Specifically, using atactic triblock copolymers with the same overall composition of styrene (S) and p ‐bromostyrene ( p BrS) units, but with two different block arrangements, that is, p BrS 90 ‐ b ‐S 120 ‐ b ‐ p BrS 90 (I) and S 60 ‐ b ‐ p BrS 180 ‐ b ‐S 60 (II), which are indistinguishable by NMR, we detected a dramatic difference in their molar Kerr constants ( m K ), in agreement with those previously estimated. Although similar in magnitude, their Kerr constants differ in sign, with m K (II) positive and m K (I) negative. In addition, S/ p BrS random and gradient copolymers synthesized by reversible addition‐fragmentation chain‐transfer (RAFT) polymerization exhibit a heretofore unexpected enhanced enchainment of racemic ( r ) p BrS‐ p BrS diads. Comparison of their observed and calculated m K s suggests that the gradient S/ p BrS copolymers possess an unanticipated additional gradient in stereosequence that parallels their comonomer gradient, that is, as the concentration of p Brs units decreases from one end of the copolymer chain to the other, so does the content of r diads. This conclusion could only be reached by comparison of observed and calculated Kerr effects, which access the global properties of macromolecules, and not NMR, which is only sensitive to local polymer structural environments, but not to their locations on the copolymer chains. Molar Kerr constants are characteristic of entire polymer chains and are highly sensitive to their constituent microstructures and their distribution along the chain. They may be used to both identify constituent microstructures and locate them along the polymer chain, thereby enabling, for the first time, characterization of their complete macrostructures. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013}, number={9}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, author={Hardrict, S. N. and Gurarslan, R. and Galvin, C. J. and Gracz, H. and Roy, D. and Sumerlin, B. S. and Genzer, J. and Tonelli, A. E.}, year={2013}, month={May}, pages={735–741} }