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Mesostructured particulate silica materials with tunable pore size: Synthesis, characterization and applications
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231). (Ytkemi)
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Colloidal assemblies of surfactants and polymers in aqueous solutions have been used by human mankind for hundreds of years and they are of great importance in many of our technological processes, such as fabrication of soap and papermaking. Less than two decades ago the idea of using colloidal assemblies as templates of inorganic materials was borne. A new population of materials, referred to as surfactant templated materials, took form. These materials showed extraordinary properties such as monodisperse pore size distribution, large surface areas and pore volumes.

 

The main focus of this thesis has been on synthesis and functionalisation of spherical mesostructured silica particulate materials. In the first part of the work, mesostructured materials with expanded pores have been produced using a well established aerosol-based method as well as the newly developed emulsion and solvent evaporation (ESE) method. Increase in pore size was realized through using Pluronic block copolymer F127 together with a swelling agent poly(propylene glycol) as template. The influence of the swelling agent on pore size expansion was shown to have a roughly linear relationship. Furthermore, the impact of synthesis parameters on internal and exterior morphology has been investigated. Accessibility of the internal pore space, as well as the external surface roughness were shown to be highly dependent on synthesis temperature. Additionally, a very interesting well ordered 3D closed packed (P63/mmc) material was produced using the ionic surfactant C16TAB as template in the ESE method.

 

In the second part of the thesis work, mesoporous spheres with large pore size, having either hydrophilic or hydrophobic surface properties, were used as carriers of an enzyme, lipase. The enzymatic activity of lipase was increased onto the hydrophobic surface, compared to lipase immobilized into the hydrophilic support as well as for lipase free in solution. This effect was probably due to a combination of enhanced hydrophobic interactions preventing denaturation of the enzyme and interfacial activation of the enzyme.  This study generated an inorganic carrier material that is a promising candidate for biocatalysis applications. Additionally, mesoporous spheres were used as carriers of a model drug, Ibuprofen, to study the effect of polyelectrolyte multilayers on release properties. However, these layers were shown impermeable independent on pH and the substance was only released from uncoated particles.

Place, publisher, year, edition, pages
Stockholm: KTH , 2009. , 70 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2009:8
Keyword [en]
Mesoporous materials, aersol-based process, emulsion-based process, biocatalysis, sustained release, 3D hexagonal, 2D hexagonal, powder, spherical particles, liquid crystalline phases, AFM-porosimetry, Pluronic
National Category
Other Basic Medicine
Identifiers
URN: urn:nbn:se:kth:diva-10089ISBN: 978-91-7415-243-2 (print)OAI: oai:DiVA.org:kth-10089DiVA: diva2:207908
Public defence
2009-04-03, E2, Lindstedsvägen 3, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20100811

Available from: 2009-03-19 Created: 2009-03-11 Last updated: 2014-11-03Bibliographically approved
List of papers
1. Expansion of the F127-templated mesostructure in aerosolgeneratedparticles by using polypropylene glycol as a swelling agent
Open this publication in new window or tab >>Expansion of the F127-templated mesostructure in aerosolgeneratedparticles by using polypropylene glycol as a swelling agent
2008 (English)In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 113, 1-13 p.Article in journal (Refereed) Published
Abstract [en]

Expansion of the mesostructure in aerosol-generated particles was performed through incorporation of polypropylene glycol (PPG), a non-volatile swelling agent. TEOS was used as silica source and the Pluronic block copolymer, F127, as template. The ratio of TEOS to F127 was kept constant during synthesis, while varying the weight ratio of PPG to F127 systematically. The impact of the PPG on the expansion of the structure was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and nitrogen adsorption. Different methods were used to calculate the pore size distributions, the BJH, the BdB-FHH, the KJS and the NLDFT method. Simple geometrical models of the expansion were derived to interpret the experimental data and establish their accuracy. Experimental data showed a roughly linear expansion of the unit cell and pore size, consistent with that expected by modelling the swelling of a hexagonal (p6mm) structure assuming constant wall thickness. The expansion is increasing as a function of increasing PPG/F127 ratio by about 25 Å. An expression of the density of the silica wall was calculated from the models resulting in a density of 1.95 ± 0.2 g/cm3. At a PPG/F127 ratio of approximately 0.31, the p6mm structure (found at lower PPG/F127 ratios) transforms to a microemulsion-templated foam structure. At an even higher PPG/F127 ratio (0.63–1.56), phase separation of the oil from the swollen template occurred, yielding a two-phase system of coexisting foam and large vesicles.

Keyword
Polypropylene glycol; Expanded pores; Swelling agent; Mesoporous particles; F127; Aerosol; Nitrogen adsorption; Geometrical models; NLDFT; BdB-FHH; KJS
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-10102 (URN)10.1016/j.micromeso.2007.10.045 (DOI)000257362100002 ()
Note

QC 20100811

Available from: 2009-03-19 Created: 2009-03-19 Last updated: 2017-12-13Bibliographically approved
2. AFM-Porosimetry: Density and pore volume measurements ofparticulate materials
Open this publication in new window or tab >>AFM-Porosimetry: Density and pore volume measurements ofparticulate materials
Show others...
2008 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, 7024-7030 p.Article in journal (Refereed) Published
Abstract [en]

We introduced the novel technique of AFM-porosimetry and applied it to measure the total pore volume of porous particles with a spherical geometry. The methodology is based on using an atomic force microscope as a balance to measure masses of individual particles. Several particles within the same batch were measured, and by plotting particle mass versus particle volume, the bulk density of the sample can be extracted from the slope of the linear fit. The pore volume is then calculated from the densities of the bulk and matrix materials, respectively. In contrast to nitrogen sorption and mercury porosimetry, this method is capable of measuring the total pore volume regardless of pore size distribution and pore connectivity. In this study, three porous samples were investigated by AFM-porosimetry: one ordered mesoporous sample and two disordered foam structures. All samples were based on a matrix of amorphous silica templated by a block copolymer, Pluronic F127, swollen to various degrees with poly(propylene glycol). In addition, the density of silica spheres without a template was measured by two independent techniques: AFM and the Archimedes principle.

Keyword
atomic-force microscope; size-exclusion chromatography; nmr cryoporometry; adsorption hysteresis; cantilever sensors; functional theory; gas-adsorption; nitrogen; mcm-41; liquid
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-10103 (URN)10.1021/la800260h (DOI)000257101100086 ()2-s2.0-47349113900 (Scopus ID)
Note

QC 20100811

Available from: 2009-03-19 Created: 2009-03-19 Last updated: 2017-12-13Bibliographically approved
3. Control of internal (2D and 3D hexagonal) mesostructure andparticle morphology of spherical mesoporous silica particlesusing the emulsion and solvent evaporation (ESE) method
Open this publication in new window or tab >>Control of internal (2D and 3D hexagonal) mesostructure andparticle morphology of spherical mesoporous silica particlesusing the emulsion and solvent evaporation (ESE) method
2009 (English)In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 120, 359-367 p.Article in journal (Refereed) Published
Abstract [en]

In this study we demonstrate the opportunities controlling internal structure as well as exterior morphology of surfactant templated mesostructured materials through the newly developed emulsion and solvent evaporation (ESE) method. In particular, we consider the control of synthesis temperature and map the influence upon both internal structure and surface morphology of particles templated by the temperature sensitive Pluronic block copolymer F127. Furthermore, we vary compositions, by adding poly(propylene glycol) acting as a swelling agent, as well as by controlling the moisture content. Both of these are having an impact on the internal mesostructure as well as the pore size. Apart from probing internal structure by scattering techniques, the accessibility of the mesoscopic pores of these materials are investigated by measuring the adsorption of a cationic dye, Janus Green B, into the materials. This method shows that accessibility varies dramatically with internal structure.Further, by carefully controlling the moisture content when using the cationic surfactant C(16)TAB as template, a well ordered 3D hexagonal closed packed (P6(3)/mmc) material with large surface area as well as pore volume was prepared. This further indicates the versatility of the new preparation technique.

Keyword
ESE method; Mesoporous materials; Spherical particles; Expanded pores; Pluronic F127; C(16)TAB; Morphology control; Poly(propylene glycol); 3D hexagonal; P6(3)/mmc
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-10104 (URN)10.1016/j.micromeso.2008.12.002 (DOI)000264971200025 ()
Note
QC 20100811Available from: 2009-03-19 Created: 2009-03-19 Last updated: 2017-12-13Bibliographically approved
4. Improved enzymatic activity of Thermomyces lanuginosus lipaseimmobilized in a hydrophobic particulate mesoporous carrier
Open this publication in new window or tab >>Improved enzymatic activity of Thermomyces lanuginosus lipaseimmobilized in a hydrophobic particulate mesoporous carrier
2010 (English)In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 343, no 1, 359-365 p.Article in journal (Refereed) Published
Abstract [en]

Lipase from Thermomyces lanuginosus has been immobilized within particulate mesoporous silica carriers, with either hydrophilic or hydrophobic supporting surfaces, produced by the newly developed emulsion and solvent evaporation (ESE) method. The Michaelis-Menten model was used to calculate the parameters related to the enzymatic activity of lipase i.e. the turnover number, k(cat), and the specific activity. The specific activity was improved by immobilization of lipase onto the hydrophobic support, compared to lipase immobilized onto the hydrophilic support and lipase free in solution. The enhanced enzymatic activity of lipase onto a hydrophobic support was attributed to interfacial activation of the Thermomyces lanuginosus lipase when it is attached to a hydrophobic surface and a reduced denaturation. Confocal scanning laster microscopy (CLSM) studies, of fluorescently tagged lipase, showed that leakage of the lipase from the mesoporous particles was limited to all initial period of only a few hours. Both the rate and the amount of lipase leached were reduced when the lipase was immobilized onto the hydrophobic support.

Keyword
Lipase; Mesoporous; CLSM; Particulate; Carries; Enzymatic activity; Supporting surfaces
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-10105 (URN)10.1016/j.jcis.2009.11.014 (DOI)000274548900050 ()
Note
Uppdaterad från manuskript till artikel: 20100811 QC 20100811Available from: 2009-03-19 Created: 2009-03-19 Last updated: 2017-12-13Bibliographically approved
5. Sustained Release of Ibuprofen from Polyelectrolyte Encapsulated Mesoporous Carriers
Open this publication in new window or tab >>Sustained Release of Ibuprofen from Polyelectrolyte Encapsulated Mesoporous Carriers
2009 (English)In: Journal of Dispersion Science and Technology, ISSN 0193-2691, E-ISSN 1532-2351, Vol. 30, no 6, 892-902 p.Article in journal (Refereed) Published
Abstract [en]

Polyelectrolyte multilayers are receiving much attention due to their insoly. and due to structural responses induced in them by changes in soln. properties such as, for example, temp., pH or ionic strength.  These characteristics make polyelectrolyte multilayers highly interesting in encapsulation technol. and controlled delivery applications.  However, producing dry, biocompatible formulations for storage of low mol. wt. substances poses a challenge.  One possibility is to make use of a well-defined mesoporous inorg. carrier material as host for the model substance (in the authors' case ibuprofen).  Control over release properties are enabled by polyelectrolyte encapsulation of the inorg. carrier.  The authors built such multilayers through consecutive deposition of PAH and PSS on top of a first layer of PEI.  These layers were adsorbed either in presence or absent of ibuprofen.  The influence of long time storage, 2 years, of the samples was also investigated.  The polyelectrolyte multilayer structure was investigated in detail by Dual Polarization Interferometry (DPI), and the authors use these data to interpret the measured release profiles.

Place, publisher, year, edition, pages
Taylor & Francis, 2009
Keyword
Dual polarization interferometry (DPI); ibuprofen; mesoporous particles; polyelectrolyte encapsulation; release properties
National Category
Other Chemistry Topics
Identifiers
urn:nbn:se:kth:diva-70229 (URN)10.1080/01932690802644095 (DOI)000266436200019 ()2-s2.0-70449337774 (Scopus ID)
Note
QC 20120207Available from: 2012-02-07 Created: 2012-01-30 Last updated: 2017-12-08Bibliographically approved

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