Romanian Academy

About: Romanian Academy is a archive organization based out in Bucharest, Romania. It is known for research contribution in the topics: Population & Nonlinear system. The organization has 3662 authors who have published 10491 publications receiving 146447 citations. The organization is also known as: Academia Română & Societatea Literară Română.

Phases investigation in the antimony doped Bi2O3 system

Abstract: The present study investigates the influence of Sb ions, introduced as dopants in α-Bi 2 O 3 , on the structure of the oxide polymorph forms obtained at high temperature. The structural changes of α-Bi 2 O 3 for compositions in the system Bi 2-x Sb x O 3 (x=0, 0.05, 0,1, 0.15, 0.2), at different thermal treatment temperatures were analyzed by thermal analysis, powder X-ray diffraction and infrared transmission spectroscopy. A tendency of the structure to change to a higher symmetry (monoclinic → tetragonal → cubic) was observed, as the content in antimony increased and the temperature reached 850 °C. The presence of Sb 2 O 3 in the Bi 2 O 3 oxide system promotes an oxygen release from the oxide and enlarges the stabilization domain of the δ-phase.

Covalent Poly(2‐Isopropenyl‐2‐Oxazoline) Hydrogels with Ultrahigh Mechanical Strength and Toughness through Secondary Terpyridine Metal‐Coordination Crosslinks

Abstract: The present study reports the synthesis of poly(2-isopropenyl-2-oxazoline) (PiPOx) dual-crosslinked hydrogels by both covalent and physical (i.e., metal-ligand coordination) interactions. First, chemical crosslinking of a modified PiPOx polymer containing terpyridine (TPy) unit is achieved by reacting with azelaic acid (non-anedioic acid). Transient crosslinks are subsequently introduced by complexation of the TPy units with different divalent transition metal ions. This strategy provides access to hydrogels with superior mechanical properties compared to the pure covalently crosslinked PiPOx hydrogels. The mechanical properties and water uptake of the hydrogels could be easily controlled by swelling in different aqueous metal ion solutions. PiPOx hydrogels swollen in Zn2+ solution are found to possess ultrahigh compression strength (9 MPa), remarkable toughness (99 MJ m(-3)) and outstanding self-recoverability (98% toughness recovery after swelling for 60 min without external stimuli), which are among the highest reported in literature to date. These remarkable properties are assigned to the thermodynamically stable, but kinetically labile Zn2+-TPy complexes that produce a dynamic network with fewer imperfections and better adaptive properties under mechanical stress compared to those with other metal ions.

Defined High Molar Mass Poly(2‐Oxazoline)s

Abstract: Poly(2-alkyl-2-oxazoline)s (PAOx) are regaining interest for biomedical applications. However, their full potential is hampered by the inability to synthesise uniform high-molar mass PAOx. In this work, we proposed alternative intrinsic chain transfer mechanisms based on 2-oxazoline and oxazolinium chain-end tautomerisation and derived improved polymerization conditions to suppress chain transfer, allowing the synthesis of highly defined poly(2-ethyl-2-oxazoline) s up to ca. 50 kDa (dispersity (D) < 1.05) and defined polymers up to at least 300 kDa (D < 1.2). The determination of the chain transfer constants for the polymerisations hinted towards the tautomerisation of the oxazolinium chain end as most plausible cause for chain transfer. Finally, the method was applied for the preparation of up to 60 kDa molar mass copolymers of 2-ethyl2- oxazoline and 2-methoxycarbonylethyl-2-oxazoline.