Associated inter‐ and intrachain conformational transitions in polystyrene solutions

Abstract

Understanding the conformational changes of polymeric chains in solutions is an essential and integral part of polymer physics. By increasing the concentration of polymer solutions from dilute to semidilute regime, the critical chain overlapping has been reported at the concentration termed as C*. In this study, the associated inter‐ and intrachain conformational transitions in polystyrene (PS) solutions are reported. By comparing the spectroscopic intensity ratio versus concentration for an intrachain PS system, a break point was observed in good solvent which coincided with the theoretically predicted C*. Moreover, the intrachain conformation showed no obvious change below C*, while significant collapse started to occur above C*. This result reveals a new insight in polymer physics, since traditionally the size of polymer chains is considered to decrease weakly regarding the concentration change in the semidilute regime. It is important to find such an abrupt intrachain conformational transition between the dilute and semidilute solutions and provide the first experimental observation that inter‐ and intrachain conformational transitions are correlated to one the other. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 1373–1379

Conformational Transitions of Polymer Chains in Solutions Characterized by Fluorescence Resonance Energy Transfer

“…Makarow considered that donor–acceptor diffusion occurs in three dimensions and related an equation, Rrms=(6normalDsans-serifτD)1/2 [50]. For PS with M n = 200,000 Da, 0.4 units of Cz and 2.2 units of An exist on a signal chain, which results in a relatively large distance between An and Cz that makes the diffusion item negligible [24]. However, for PS with M n = 13,000 Da, the diffusion-enhanced FRET becomes non-negligible.…”

“…Contrary to this, Torkelson claimed that in a polystyrene (PS) system between dilute and semidilute solutions, there was no abrupt transition found by using excimer fluorescence spectroscopy [23]. In addition to the excimer fluorescence technique, fluorescence resonance energy transfer (FRET) has been employed to study polymer conformation transition [24,25,26,27]. According to the theory of Förster, FRET efficiency is inversely proportional to the sixth power of the distance between donor and acceptor, and the effective distance range is 0.5–10 nm [28].…”

Low Dielectric Constant and Anisotropic Mechanical Properties of Dispenser‐Printed Polyetherimide Films Using Two‐Step Thermal Treatment

“…As polymers show a complex frame of interwoven relationships among the structure, process, and physical properties, understanding the distinct characteristics of polymers before and after solution processing is important in terms of their structure and morphology. [ 25–29 ]…”

“…As polymers show a complex frame of interwoven relationships among the structure, process, and physical properties, understanding the distinct characteristics of polymers before and after solution processing is important in terms of their structure and morphology. [25][26][27][28][29] In this study, we investigated the characteristics of PEI films fabricated by dispenser printing, that is, dielectric constant, CTE, tensile strength, and modulus. N-Methyl pyrrolidone (NMP) was chosen as the solvent to dissolve PEI, and printing condition optimization was conducted based on the pressure and rheological properties of the PEI ink.…”

Σύνθεση Πολυμερικών/Οργανικών Νανοσωματιδίων Με Καλά Καθορισμένες Διαστάσεις Και Μελέτη Της Επίδρασής Τους Στις Ιδιότητες Μη Γραμμικών Πολυμερών Σε Διάλυμα Και Τήγμα

“…Σχήμα 38: Μηχανισμός σύνθεσης κυκλικού πολυστυρενίου σε τρία στάδια α) ATRP, β) πυρηνόφιλης υποκατάστασης βρωμίου από αζίδιο, γ) κυκλοποίηση μέσω αντίδρασης "κλικ". κρίσιμη συγκέντρωση, c) ημιαραιό διάλυμα 61…”