Core-shell nanoparticles
a nanoparticle and core shell technology, applied in the direction of liquid/solution decomposition chemical coating, instruments, drug compositions, etc., can solve the problems of loss of mechanical properties, prior art, difficulty in making such coatings on an industrial scale, etc., and achieve high porosity.
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example 1
[0090]PDPA23-PDMA68 diblock copolymer was synthesised by sequential monomer addition using group transfer polymerisation according to the methods described in ‘Bütün, V.; Armes, S. P.; Billingham, N. C. Chem. Commun. 1997, 671-672’. Gel permeation chromatography analysis indicated an Mn of 18,000 and an Mw / Mn of 1.08 using a series of near-monodisperse poly(methyl methacrylate) calibration standards. The mean degrees of polymerisation of the PDPA and PDMA blocks were estimated to be 23 and 68, respectively, using 1H NMR spectroscopy.
[0091]Non-crosslinked micelles of the PDPA23-PDMA68 diblock copolymer (degree of quaternisation=0%) were prepared by molecular dissolution at pH 2, followed by adjusting the solution pH to pH 7.2 using NaOH. Dynamic light scattering (DLS) studies at 25° C. indicated an intensity-average micelle diameter of 37 nm for a 0.25 wt.% copolymer micelle solution at pH 7.2.
[0092]Silicification of the said micelles was achieved by mixing 2.0 ml of an aqueous micel...
example 2
[0093]PDPA23-PDMA68 diblock copolymer was synthesised by sequential monomer addition using group transfer polymerisation as in Example 1.
[0094]Partial quaternisation of the PDMA block (targeting a degree of quaternisation of either 50% or 100%) using iodomethane was conducted in THF for 24 hours, as described in ‘Bütün,V.; Armes, S. P.; Billingham N. C. Macromolecules 2001, 34, 1148-1159’.
[0095]Non-crosslinked micelles prepared using either 50% or 100% quaternised PDPA23-PDMA68 diblock copolymers were also prepared by pH adjustment, as described in Example 1. DLS studies conducted at pH 7.2 indicated intensity-average diameters of 29 nm and 26 nm for 0.25 wt. % aqueous solutions of 50% and 100% quaternised copolymer micelles, respectively.
[0096]Tetramethyl orthosilicate (1.0 ml) was added at 20° C. to 2.0 ml of a 0.25 wt. % aqueous solution of PDPA23-PDMA68copolymer micelles in which the PDMA chains were 50% quaternised, and silica deposition was allowed to continue for 20 minutes, ...
example 3
[0098]PDPA23-PDMA68 diblock copolymer was synthesised by sequential monomer addition using group transfer polymerisation, and non-crosslinked micelles of the PDPA23-PDMA68 diblock copolymer were prepared as described in Example 1.
[0099]Shell crosslinking of the coronal PDMA chains was achieved by adding a bifunctional quaternising agent, 1,2-bis-(2-iodoethoxy)ethane (BIEE, 0.15 moles per DMA residue for a target degree of cross-linking of 30%) to a 0.25% PDPA23-PDMA68 copolymer micelle solution at pH 7.2. Shell crosslinking was carried out at 25° C. for at least 72 hours. After shell crosslinking, DLS studies indicated an intensity-average diameter of 32 nm and TEM studies suggested a number-average diameter of 26 nm for the dried SCL micelles. On adjusting the aqueous SCL micelle solution to pH 2, DLS studies indicated an intensity-average diameter of 45 nm due to swelling of the SCL micelles.
[0100]This DLS experiment also confirmed successful shell crosslinking, since the non-cros...
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