Characterization of silica–polymer aerogel composites by small-angle neutron scattering and transmission electron microscopy

Hu, Xiangjun; Littrel, Kenneth; Ji, Shuang; Pickles, D.; Risen, William M.

doi:10.1016/s0022-3093(01)00625-1

Cited by 47 publications

(34 citation statements)

References 9 publications

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“…One of the most abundant organic polymers is chitin, a polyglucosamide, which contains exoskeletons of insects, cell walls, etc. Chitin itself is not applicable for sol-gel processes, but its derivative, chitosan, being obtained by alkaline deacetylation of chitin can be used for this purpose [36,37]. Chitosan is commercially available and its biocompatibility is proved.…”

Section: Aerogels Based On Biopolymers As Drug Carriersmentioning

confidence: 99%

Pharmaceutical Applications of Aerogels

Смирнова

2011

Aerogels Handbook

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At present, an interest has grown in the field of biocompatible aerogels and composite aerogel materials in life science, especially in biomedical and pharmaceutical applications. Due to their large surface area, open pore structure, and biocompatibility, aerogels are very promising candidates for drug delivery systems. The use of both inorganic and organic aerogels as carriers for pharmaceutically active compounds is discussed in this chapter. Both the stability and the release kinetics of the drug can be significantly improved by loading them into aerogels. First attempts to prepare semisolid and solid pharmaceutical formulations have been made. Furthermore, aerogels can be used as a host matrix for bioactive compounds (enzymes and proteins), which improve or enable their performance. Taking into account all research activities in the area of aerogels, a number of promising pharmaceutical applications can be expected in future. IntroductionSilica aerogels were used in daily life products since 1960s, when Monsanto's aerogels were introduced as additives for cosmetics and toothpaste. At present, an interest has grown in the field of biocompatible aerogels and composite aerogel materials in life sciences, especially for biomedical and pharmaceutical applications. In principle, biocompatible aerogels can be made from any organic compound, whose properties such as toxicity and biodegradation are suitable for the given application. In the case of aerogel composites, the final material consists of an aerogel matrix and one or more additional phases (of any composition or scale), which influence the properties of the final product. Thus, at least one phase has a physical structure with dimensions in the order of nanometres (the particles and pores of the aerogel). The aerogel composites can be prepared in two different ways: through the addition of a target compound during the sol-gel process (Figure 31.1A) and by post-treatment of the dried aerogels (Figure 31.1B), for example, by adsorption, vapour phase deposition, or reactive gas treatment.The first method (a) is attractive by its simplicity and flexibility, since virtually every material can be easily added to the sol solution before gelation. This added material can be of I. Smirnova

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Section: Aerogels Based On Biopolymers As Drug Carriersmentioning

confidence: 99%

Pharmaceutical Applications of Aerogels

Смирнова

2011

Aerogels Handbook

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“…Hu and coworkers further investigated the structure by small angle neutron scattering (SANS) and found that they have fractal dimensionalities, D f , of 2.47 for SiO 2 -15%X to 2.69 for SiO 2 -5%X aerogels [9]. Recall that for three-dimensional systems with no density variation, D f ¼ 3.…”

Section: Propertiesmentioning

confidence: 99%

“…The lower the value of D f , the more open the structure is. The original analysis reported by Hu et al [9] also yielded values for the exponential cutoff length, ς, which essentially shows the distance through a structure over which there is information coherence. The values of, ς, for these materials vary from 3.8 to 5.9 nm, while those for the SiO 2 -X-M aerogels vary over a slightly wider range.…”

Section: Propertiesmentioning

confidence: 99%

Biopolymer-Containing Aerogels: Chitosan-Silica Hybrid Aerogels

Yao¹,

Liu

Risen

2011

Aerogels Handbook

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Hybrid aerogels comprising bioderived polymers and metal oxides have been explored in the case of chitosan and silica. The physical properties of homogeneous aerogels have been explored extensively and structural models have been formulated on the basis of the data. One attractive feature of these materials is that the chemically functional groups on chitosan can be employed to develop transparent transition-and lanthanide-containing monolithic aerogels. The functionality and chemical properties also enable formation of aerogels with a range of magnetic properties, with gold and other nanoparticles, and with attached polymeric structures. The structure and chemistry make it possible to explore diffusion control of reactions and physico-chemical control of nanoparticle growth. Some biocompatibility data are described. IntroductionOne class of organic-inorganic hybrid aerogels is a combination of a bioderived organic polymer and silica. Of particular interest in this class are aerogels that comprise chitosan or other polysaccharides which have functional groups that enable them to interact both with the silica-based components of the aerogel and with compounds that are added subsequently. The latter can be metal ions or any of a range of species that can react with or coordinate to pendant -NH 2 or carbohydrate -OH groups, in the case of chitosan. In the case of the polysaccharides pectic acid and alginic acid, the pendant groups are carboxyl, -COOH, and -OH, while in gellan gum and carrageenans, neutralized carboxylic groups, -COOM (typically, M ¼ Na

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“…Chitosan silica aerogels in transparent or translucent monolithic solid form have been synthesized by an initial sol-gel process, followed by extraction with supereritical CO 2 [1][2][3][4][5][6]. The chitosan silica aerogels have high porosity, up to 95%(v/v), and densities ranging from 0.2 to 0.3g/cm 3 .…”

Section: Introductionmentioning

confidence: 99%

“…The chitosan silica aerogels have high porosity, up to 95%(v/v), and densities ranging from 0.2 to 0.3g/cm 3 . The chitosan silica aerogels have average pore size of 3-5nm [2][3]. They have a three dimensional network which can be thought of as a Si-O-Si bonded framework with the chitosan polymer winding through the network like a snake that interacts with silica by both hydrogen bonds and Si-O-C bonds.…”

Section: Introductionmentioning

confidence: 99%

Polymer-Attached Functional Inorganic-Organic Hybrid Nano-composite Aerogels

2002

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ABSTACTNovel materials in which modified inorganic-organic hybrid silica aerogels are attached to polymer chains have been synthesized. The aerogels are based on chitosan, a bioderived polymer from chitin, and they contain silica. The first stage of the modifications includes attachment of isocyanate, amine onto the chitosan chains embedded within the aerogel. These groups are employed in the second stage to develop the reactions required to "string" aerogel particles along functionalized linear polymers or to employ these polymers to crosslink the composite aerogels. The initial chitosan-silica aerogel particles have an ultimate size of about 2nm, and their functionally modified forms were reacted at sizes up to 1 jum. These aerogels can take up and hold dyes and water-soluble drugs. The chemistry to synthesize polyamino-siloxane based aerogel composite was discussed. In addition, two approaches to synthesize PHEMA aerogel hybrid were studied. INTRODUCTIONChitosan silica aerogels in transparent or translucent monolithic solid form have been synthesized by an initial sol-gel process, followed by extraction with supereritical CO 2 [1-6]. The chitosan silica aerogels have high porosity, up to 95%(v/v), and densities ranging from 0.2 to 0.3g/cm 3 . The chitosan silica aerogels have average pore size of 3-5nm[2-3]. They have a three dimensional network which can be thought of as a Si-O-Si bonded framework with the chitosan polymer winding through the network like a snake that interacts with silica by both hydrogen bonds and Si-O-C bonds.In recent work, we have demonstrated that the amine groups on the chitosan in the silica network are able to react with externally provided compounds. Thus, it is possible to carry out reactions on the chitosan molecule that is essentially suspended in the dry aerogel space. That makes it feasible to do chemical reactions where water must be excluded on a molecule (chitosan) that otherwise would only be available in solvents with active hydrogen [7]. Small molecules such as bis (4-isocynatocyclohexyl) methane (HMDI), succinic anhydride (SA), isocyanatoethyl methacrylate (LEMA), and dansyl chloride (DC) have been used in this work to modify the chitosan in aerogel through chemical reactions with amines present in chitosan [7].Of particular interest are the reaction of HMDI with chitosan silica aerogel, which results in a new -NCO terminated material, and, the reaction of IEMA with chitosan silica aerogel to produce a methacrylate terminated new aerogel material. They are valuable not only because they have new physical properties, but also because they bring new functional groups into these aerogels, making it possible to carry out new chemistries. This should lead to novel materials with varied properties.One possibility is to attach these -NCO terminated aerogel particles in the 100nm to Igm size range to linear polymers such as poly (allyamine), aminopropylmethylsiloxane-dimethylsiloxane copolymer, or poly (2-hydroxyethyl methacrylate) (PHEMA).The aminopropylmethylsiloxane-co-dimet...

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Characterization of silica–polymer aerogel composites by small-angle neutron scattering and transmission electron microscopy

Cited by 47 publications

References 9 publications

Pharmaceutical Applications of Aerogels

Pharmaceutical Applications of Aerogels

Biopolymer-Containing Aerogels: Chitosan-Silica Hybrid Aerogels

Polymer-Attached Functional Inorganic-Organic Hybrid Nano-composite Aerogels

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