01694nas a2200169   4500008004100000022001400041245010300055210006900158260012500227300001100352490000800363520094400371100003101315700002101346700002701367856013001394       2007                        eng d  a0021-960600aPathway to copolymer collapse in dilute solution: uniform versus random distribution of comonomers0 aPathway to copolymer collapse in dilute solution uniform versus   aCIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USAbAMER INST PHYSICScDEC  a2349010 v1273 a<p>Monte Carlo simulations show that copolymers with uniformly (or periodically) distributed sticky comonomers collapse ``cooperatively,'' abruptly forming a compact intermediate comprising a monomer shell surrounding a core of the aggregated comonomers. In comparison, random copolymers collapse through a relatively less-compact intermediate comprising a comonomer core surrounded by a fluffy monomer shell that densifies over a wide temperature range. This difference between the collapse pathways for random and uniform copolymers persists to higher chain lengths, where uniform copolymers tend to form multiple comonomer cores. In this paper, we describe the formation of such an intermediate state, and the subsequent collapse, by recognizing that these arise from the expected balance between comonomer aggregation enthalpy and loop formation entropy dictated by the chain microstructure. (c) 2007 American Institute of Physics.</p>1 aDasmahapatra, Ashok, Kumar1 aNanavati, Hemant1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/pathway-copolymer-collapse-dilute-solution-uniform-versus-random-distribution-comonomers-002030nas a2200253   4500008004100000022001400041245006800055210006400123260012500187300001100312490000800323520114800331653001401479653002001493653002001513653001701533653001401550653002401564653001801588100003101606700002101637700002701658856009101685       2009                        eng d  a0021-960600aPolymer crystallization in the presence of ``sticky'' additives0 aPolymer crystallization in the presence of sticky additives  aCIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USAbAMER INST PHYSICScAUG  a0749050 v1313 a<p>The effect of ``sticky'' additives (viz., those that have attractive interactions with the polymer) on polymer crystallization, has been investigated by dynamic Monte Carlo (DMC) simulations. Additive-polymer attractive interactions result in a slowing down of the polymer chain diffusivity in the melt state. Our results show that with increasing additive stickiness, polymer crystallinity decreases monotonically, and thinner crystallites form, viz., crystallization is inhibited by the presence of sticky additives. Unusually, the observed ``specific heat'' peak at the phase transition shows nonmonotonic behavior with additive stickiness, and exhibits a maximum for intermediate values of additive stickiness. While the origins of this unexpected behavior are not clear, we show that it correlates with a large interchange between crystalline and amorphous states of the monomers, in the vicinity of the additives. At this intermediate additive stickiness, we also find that crystallization follows a qualitatively different route-crystallinity shows a non-Avrami-like evolution, unlike the case at low or high additive stickiness.</p>10aAdditives10aamorphous state10acrystallisation10acrystallites10aDiffusion10aMonte Carlo methods10apolymer melts1 aDasmahapatra, Ashok, Kumar1 aNanavati, Hemant1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/polymer-crystallization-presence-sticky-additives-0