Naslov
Utilisation of complexation for gaining control over hydrolysis in the course of the sol-gel process

Autori
Mandić, Vilko ; Kurajica, Stanislav

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Book of Abstracts / Garcia Gonzales, Carlos - Coimbra, 2019, 1-1

Skup
Aerogels 2019

Mjesto i datum
Coimbra, Portugal, 21.10.2019. - 23.10.2019

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
Complexation, Sol-gel, Alkoxide, Ethyl acetoacetate, NMR, Titania, Alumina

Sažetak
This investigation presents the ability to influence and control the course of the hydrolysis and polycondensation stages of the sol-gel synthesis of the commonly used oxide nanomaterials (titania and alumina). The course of the preparation of sols using sol-gel method is known to be both complex and sensitive. However, sol-gel method generally allows achieving high-levels of homogeneity and tuning of the composition as well as advanced morphology. Despite further increased the complexity of the system, the addition of complexation agent was utilised as a tool to influence the rate of the hydrolysis reaction by means of chemical shielding. Here we monitor the effect of changing the ratio of the main precursors, alkoxides (TNB ; titanium n-butoxide and ASB ; aluminium sec-butoxide) to β-diketone complexing agent (EAA ; ethyl acetoacetate), where the compounds obtained, their structure and quantitative relationships were focused. PXRD, FTIR, UV-VIS, 1D & 2D (COSY, HSQC, DOSY) NMR techniques were used to identify forming species and allow understanding of the mechanisms and extent of their reactions. In the titania system 3 compounds ; bis-chelated monomer, bis-chelated and monochelated dimer have been observed. With EAA increase the coordination shifts from dimer (mono- and bis-chelated) toward monomer (bis-chelated). The transesterification and partly hydrolysed habitus of the prepared sols were observed (some of the butoxy & EAA groups remained attached to titanium). High EAA content retarded the anatase crystallisation. In alumina system the obtained products were: tris-chelated monomer, bis-chelated, tris-chelated and tetra-chelated dimmer and monochelated trimer. Of the formed oligomers, this is the first evidence of tris-chelated dimmer for any alkoxide & β-ketoester or β-diketone combination. Of the formed complexes, this is the first evidence of bis-chelated and tetra-chelated dimmer for ASB and EAA combination. High EAA content shifts the Al coordination to six.

Izvorni jezik
Engleski

Znanstvena područja
Kemija, Kemijsko inženjerstvo, Interdisciplinarne tehničke znanosti

POVEZANOST RADA