Epoxy resins and networks with anisotropic properties

Abstract

BEATA MOSSETY-LESZCZAK *)1) , HENRYK GALINA 1) , MAGDALENA W£ODARSKA 2) , MARCIN KOWALIK 3) , KRZYSZTOF £OKAJ 4) , ZBIGNIEW FLORJAÑCZYK 4) ywice i sieci epoksydowe o w³aoeciwooeciach anizotropowych Autorzy dedykuj¹ publikacjê Pani Profesor Marii Nowakowskiej (Uniwersytet Opolski) z okazji Jubileuszu 80-lecia Jej urodzin i 50-lecia pracy naukowej. Streszczenie-Na podstawie literatury podano ogóln¹ charakterystykê ciek³okrystalicznych uk³adów polimerowych ze szczególnym uwzglêdnieniem uk³adów epoksydowych. W ramach badañ w³asnych przedstawiono sposób syntezy ciek³okrystalicznego monomeru diepoksydowego (LCM, schemat A), w którym ugrupowanie mezogeniczne stanowi³ czteropieroecieniowy diester aromatyczny bifenylo-4,4'-diolu. Budowê chemiczn¹ tego monomeru potwierdzono metodami FT-IR i 1 H-NMR. LCM sieciowano 4,4'-diaminodifenylometanem (DDM), 4-(N,N-dimetyloamino)pirydyn¹ (DMAP) b¹dŸ kwasem pimelinowym (KP); w charakterze nanonape³niacza w procesie utwardzania zastosowano nanoprêty z difenylofosforanu glinu (NP). Proces sieciowania badanych uk³adów (zawieraj¹cych NP albo bez tego nanonape³niacza) zbadano metod¹ skaningowej kalorymetrii ró¿nicowej (DSC), a strukturê utwardzonych kompozycji oceniono za pomoc¹ mikroskopu polaryzacyjnego i me-tod¹ rentgenograficzn¹ (WAXS). Metod¹ DSC okreoelono te¿ w³aoeciwooeci cieplne tych kompozycji po utwardzeniu. Ustalono warunki temperaturowe procesu sieciowania prowadz¹ce do powstawania sieci polimerowych charakteryzuj¹cych siê w³aoeciwooeciami anizotropowymi. Stwierdzono, ¿e przyczynê ograniczaj¹c¹ mo¿liwooeci otrzymywania materia³ów jednorodnie uporz¹dkowanych ze struk-tur¹ monodomenow¹ stanowi znaczna lepkooeae LCM w fazie smektycznej, w której rozpoczyna siê proces sieciowania. S³owa kluczowe: polimery ciek³okrystaliczne, ¿ywice epoksydowe, nanokompozyty, sieciowanie, anizotropowe sieci polimerowe, w³aoeciwooeci cieplne. EPOXY RESINS AND NETWORKS WITH ANISOTROPIC PROPERTIES Summary-A general characteristics of liquid crystalline polymer systems, especially epoxy ones, is given on the basis of literature. Own research was focused on the synthesis of liquid crystalline diepoxy monomer (LCM, Scheme A) in which a tetracyclic aromatic diester of biphenyl-4,4'-diol was a mesogenic unit. The chemical structure of this monomer was confirmed by FT-IR and 1 H NMR methods. LCM was cured with 4,4'-diaminodiphenylmethane (DDM) or 4-(N,N-dimethylamino)pyridine (DMAP) or pimelic acid (KP). Diphenyl aluminum phosphate nanorods (NP) were used as a filler during a curing. The curing processes of the compositions, containing NP or not, were studied using differential scanning calorimetry (DSC, Fig. 1 and 2, Table 1) while their structures were evaluated with use of polarization microscope (Fig. 3) and by X-ray radiography (WAXS, Fig. 4). Thermal properties of cured compositions were determined by DSC method (Fig. 5). The temperature conditions of curing allowing formation of polymer networks showing anisotropic properties were found. It was stated that high viscosity of LCM in smectic phase, in ...

Liquid‐crystalline epoxy thermosets as matrices for ordered nanocomposites—a summary of experimental studies

“…The crosslinking process was also carried out in a magnetic field which can induce monodomain order of mesogenic groups of the LCER molecules. However, as it was explained, due to high viscosity of applied LCER this effect was not observed in the obtained composites [28].…”

“…In the first part of studies, a series of liquid crystalline epoxy compounds was synthesized; their properties were reported in paper [30]. Subsequently, the research scope was extended by introducing new epoxy monomers with longer aliphatic chains and curing them with the use of different curing agents [28,29,32,36]. The molecular structures of all the synthesized materials along with the temperatures of phase transitions during heating are shown in Table 1.…”

“…A complete list of curing agents used in the studies of the curing process is presented in Table 2. Altogether, the investigations covered nine diepoxy monomers -the synthesis and basic properties of them were described elsewhere [28][29][30][31][32][33][34][35][36] -and their compositions with five curing agents. Despite having studied many mixtures, the results were not satisfactory in all the cases.…”

“…In our study, alternatively, diphenyl aluminum phosphate nanorods and octakis-[(3-glycidoxypropyl)dimethylsiloxy]octasilsesquioxane (POSS-OG) were also employed as fillers of liquid crystalline epoxy resins [28,29]. The addition of POSS-OG to the liquid crystalline epoxy matrix did not significantly change the curing process, but reduced the glass transition temperature and increased the stiffness of the composite in the glassy state (in the case of monomer composition with DDM amine, the temperature T g dropped from 1108C for plain matrix to 1018C when POSS-OG was added).…”

“…During our study we synthesized and tested many epoxy resins and investigated their basic liquid crystalline properties [28][29][30][31][32][33][34][35][36]. Curing behavior was studied with various curing agents, for example, amines: 4,4 0 -diaminodiphenylmethane (DDM) or 4-(N,N-dimethylamino)pyridine (DMAP), and pimelic acid (KP), and basic properties of compositions prepared from the synthesized diepoxy monomers were presented in several papers [28,29,[32][33][34][35]. The initial aim was to determine the optimal conditions for curing of the epoxy matrix alone, so as to obtain a solid structure with molecular orientation similar to the one occurring in liquid crystals.…”