| 1. |
- Atlas, Salima, et al.
(författare)
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Radical copolymerization of acrylonitrile with 2,2,2-trifluoroethyl acrylate for dielectric materials : Structure and characterization
- 2013
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Ingår i: Journal of Polymer Science Part A. - : Wiley. - 0887-624X .- 1099-0518. ; 51:18, s. 3856-3866
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Forskningsöversikt (refereegranskat)abstract
- Radical copolymerization based on acrylonitrile (AN) and 2,2,2-Trifluoroethyl acrylate (ATRIF) initited by AIBN was investigated in acetonitrile solution. The resulting poly(AN-co-ATRIF) copolymers were characterized by 1 H, 13 C, and 19 F NMR and IR spectroscopy, and size exclusion chromatography (SEC). Their compositions were assessed by 1 H NMR. The kinetics of radical copolymerization of AN with ATRIF was investigated from sereval experiments achieved at 70 degrees C from initial [AN](0)/[ATRIF](0) molar ratios ranging between 20/80 and 80/20 and was enabled to determine the reactivity ratios of both comonomers. From the monomer-polymer copolymerization curve, the Fineman-Ross and Kelen-Tudos laws enabled to assess the reactivity ratios (r(AN) = r(1) = 1.25 +/- 0.04 and r(ATRIF) = r(2) = 0.93 +/- 0.05 at 70 degrees C) while the revised patterns scheme led to r(12) = r(AN) = 1.03, and r(21) = r(ATRIF) = 0.78 at 70 degrees C. In all cases, rAN x rATRIF product was close to unity, which indicates that poly(AN-co-ATRIF) copolymers exhibit a random structure. This was also confirmed by the Igarashi's and Pyun's laws which revealed the presence of AN-ATRIF, AN-AN, and ATRIF-ATRIF dyads. The Q and e values for ATRIF were also assessed (Q(2) = 0.62 and e(2) = 0.93). The glass transition temperature values, Tg, of these copolymers increased from 17 to 61 degrees C as the molar percentage of ATRIF decreased from 77 to 16% in the copolymer. Thermogravimetry analysis of poly(AN-co-ATRIF) copolymers showed a good thermal stability compared to that of poly(ATRIF) homopolymer due to incorporation of AN comonomer.
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| 2. |
- Boujemaoui, Assya, et al.
(författare)
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Facile Preparation Route for Nanostructured Composites : Surface-Initiated Ring-Opening Polymerization of epsilon-Caprolactone from High-Surface-Area Nanopaper
- 2012
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 4:6, s. 3191-3198
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Tidskriftsartikel (refereegranskat)abstract
- In this work, highly porous nanopaper, i.e., sheets of papers made from non-aggregated nanofibrillated cellulose (NFC), have been surface-grafted with poly(epsilon-caprolactone) (PCL) by surface-initiated ring-opening polymerization (SI-ROP). The nanopaper has exceptionally high surface area (similar to 300 m(2)/g). The "grafting from" of the nanopapers was compared to "grafting from" of cellulose in the form of filter paper, and in both cases either titanium n-butoxide (Ti(On-Bu)(4)) or tin octoate (Sn(Oct)(2)) was utilized as a catalyst. It was found that a high surface area leads to significantly higher amount of grafted PCL in the substrates when Sn(Oct)2 was utilized as a catalyst. Up to 79 wt % PCL was successfully grafted onto the nanopapers as compared to filter paper where only 2-3 wt % PCL was grafted. However, utilizing Ti(On-Bu)4 this effect was not seen and the grafted amount was essentially similar, irrespectively of surface area. The mechanical properties of the grafted nanopaper proved to be superior to those of pure PCL films, especially at elevated temperatures. The present bottom-up preparation route of NFC-based composites allows high NFC content and provides excellent nanostructural control. This is an important advantage compared with some existing preparation routes where dispersion of the filler in the matrix is challenging.
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| 3. |
- El Ghaoui, Hanane, et al.
(författare)
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Bismuth complex catalysts for the in situ preparation of polycaprolactone/silicate bionanocomposites
- 2014
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Ingår i: Polymer international. - : Wiley. - 0959-8103 .- 1097-0126. ; 63:4, s. 709-717
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Tidskriftsartikel (refereegranskat)abstract
- Solvent-free, bismuth-catalysed in situ polymerization of caprolactone in the presence of layered silicates enables the formulation of a series of polycaprolactone/silicate bionanocomposites. Three organophilic montmorillonites obtained by cationic exchange reaction with tetrabutylammonium iodide, benzyltriethylammonium chloride and vinylbenzyltriphenylphosphonium chloride salts, respectively, were used as reinforcing reagents for these materials. The effects of clay and bismuth catalyst type (bismuth(III) acetate and triphenylbismuth) are discussed on the basis of composite morphologies and molecular weights of resulting polymers.
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