Εξειδίκευση τύπου :	Άρθρο σε επιστημονικό περιοδικό
Τίτλος:	Effects of Polymer Block Length Asymmetry and Temperature on the Nanoscale Morphology of Thermoresponsive Double Hydrophilic Block Copolymers in Aqueous Solutions
Δημιουργός/Συγγραφέας:	Vagias, Apostolos [EL] Παπαγιαννόπουλος, Αριστείδης[EN] Papagiannopoulos, Aristeidis Kreuzer, Lucas P. Giaouzi, Despoina Busch, Sebastian [EL] Πίσπας, Στέργιος[EN] Pispas, Stergios Müller-Buschbaum, Peter
Εκδότης:	American Chemical Society
Ημερομηνία:	2021
Γλώσσα:	Αγγλικά
ISSN:	0024-9297 1520-5835
DOI:	10.1021/acs.macromol.1c01005
Περίληψη:	By complementing small-angle neutron scattering (SANS) with Fourier transform infrared (FTIR) spectroscopy measurements, the influence of temperature as an external stimulus and block length asymmetry is studied on nanoscale assemblies of thermoresponsive double hydrophilic block copolymers in aqueous solutions. Morphologies and molecular hydration characteristics of two poly(N-isopropylacrylamide)-block-poly(oligo ethylene glycol methyl ether acrylate) (PNIPAM-b-POEGA) diblock copolymers, which differ in the length of the PNIPAM block, are compared. SANS provides insights into the nanostructure of the assemblies and FTIR probes vibrations of selected functional groups at the molecular level. Upon temperature increase, the solutions undergo transformations from hierarchical assemblies to more well-defined spherical morphologies. Variations in the block lengths lead to distinct morphological transformations. The variable morphological transformations originate from differences in the strength and/or amount of hydrogen bonding and hydrophobic interactions, as well as the chain density in the clusters formed and hydration. We identify transformations from hierarchical structures to fractal core–shell morphologies in the asymmetric block copolymer with the long PNIPAM block, while spherical and core–shell spherical morphologies are formed for the symmetric diblock copolymer with the short PNIPAM block. In these assemblies of PNIPAM-b-POEGA with the short PNIPAM block, the methyl side group hydration sensitively depends on the temperature increase at temperatures even beyond the nominal volume phase transition temperature. For both blocks, the evolution of the amide I band reflects that solvent–polymer interactions are still favorable even at the highest temperatures. Morphological variations after cooling to ambient temperature are reflected in both SANS and FTIR, pointing to remnant hydrogen bond interactions.
Τίτλος πηγής δημοσίευσης:	Macromolecules
Τόμος/Κεφάλαιο:	54
Τεύχος:	15
Σελίδες:	7298-7313
Θεματική Κατηγορία:	[EL] Χημική τεχνολογία[EN] Chemical technolgy [EL] Βιοχημεία[EN] Biochemistry [EL] Χημικά προϊόντα: Παραγωγή, χρήση κλπ[EN] Chemicals: Manufacture, use etc.
Λέξεις-Κλειδιά:	Cluster chemistry Morphology Polymers Scattering Thermoresponsive polymers
EU Grant:	FlexiProb
EU Grant identifier:	05K2016
Κάτοχος πνευματικών δικαιωμάτων:	© 2021 American Chemical Society
Ηλεκτρονική διεύθυνση στον εκδότη (link):	https://pubs.acs.org/doi/10.1021/acs.macromol.1c01005
Εμφανίζεται στις συλλογές:	Ινστιτούτο Θεωρητικής και Φυσικής Χημείας (ΙΘΦΧ) - Επιστημονικό έργο