Aqueous Microgels

One of the main applications for these aqueous microgels produced by IC3 is in waterborne basecoats (Aquabase) for use as clearcoat/basecoat finishes in the automotive industry. 

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The various synthetic strategies for the preparation of aqueous microgels can be divided into three groups (1) physical self-assembly or crosslinking of prepolymers in homogeneous phase or in microdroplets (2) polymerization of monomers in homogeneous phase or in microdroplets and (3) photolithographic techniques. 

The precipitation polymerization is a versatile technique and offers several advantages for the preparation of aqueous microgels ... 

Different ionic monomers were copolymerized with NIPAAm or VCL to obtain pH- and temperature-sensitive microgels. Snowden et al. [65] reported preparation of aqueous microgels by copolymerization of NIPAAm and acrylic acid (AAc) in a precipitation polymerization process. The AAc content was 5wt%. Obtained microgels displayed pH and electrolyte sensitivity, as well as temperature sensitivity. 

Lyon s group prepared aqueous microgels by copolymerization of NIPAAm with hydrophobic [tert-butyl acrylamide (TBAm)] and pH-sensitive acrylic acid monomers [73],... 

The copolymerization of different functional monomers during precipitation polymerization can be used for design of amphoteric aqueous microgels [76-82], Amphoteric microgels were prepared by copolymerization of NIPAAm with acrylic acid and vinylimidazole (Vim) [76-80], Alternatively, Tan and coworkers prepared amphoteric colloids by copolymerization of acrylic acid, 2-(diethylamino)ethyl... 

Lapeyre et al. [99] prepared aqueous microgels consisting of thermorespon-sive PNIPAAm core and thermo- and glucose-responsive poly(NIPAAm-co-acrylamidophenylboronic acid) shell. The radius of the core in the collapsed state (40°C) was 65 nm. By variation of the monomer concentrations added during the second polymerization step from 20 to 80 mM, the shell thickness increased from 15 to 38 nm. 

Fig. 17 Preparation of complexes of wedge-shaped sulfonic add molecules (TDBBSA) and PVCL/AAEM/VIm microgels by the reversible transfer from water to THF (i) transfer of the aqueous microgel to THF by solvent exchange (2) addition of TDBBSA molecules to the microgel suspension in THF and diffusion of wedge-shaped molecules into porous polymer colloids (5) fixation of TDBBSA within microgels by complexation and (4) transfer of the modified microgel to the aqueous phase by solvent exchange. TEM images of the microgels are shown. Taken from [115]...

Fig. 22 Top Modification of aqueous microgels by hydroxyapatite (HAp) nanocrystals, (a-d) TEM images of VCL/AAEM/VIm-HAp hybrid microgels containing different amounts of HAp (a) 0, (b) 7.9, (c) 34.2, and (d) 52.2 wt%. (e) EDX line scan of single microgel containing 52.2 wt% HAp with element distribution curves. Color of the lines in (e) corresponds to the color in the element distribution spectra. Reprinted from [149] with permission. Copyright 2008 American Chemical Society...

Schachschal S, Pich A, Adler H-JP (2008) Aqueous microgels for the growth of hydroxyapatite nanocrystals. Langmuir 24(9) 5129-5134... 

Pelton R (2000) Temperature-sensitive aqueous microgels. Adv Colloid Interface Sci 85 1-33... 

The major purpose of this book is to give a description of the advances made during the past two decades in the synthesis of aqueous microgels. The chemical design of microgel particles from molecular building blocks is the key for their functionalization and finally for successful application in different systems. 

Pelton, R. (2000). Temperature-sensitive aqueous microgels. Advances in Colloid and... 

Aqueous microgels are mostly spherical particles with average diameter ranging from 50 nm to 10 pm. When the size of microgels is in the submicron range, tbey are known as nanogels. Such particles are stabilized in aqueous phase by sterical mechanisms or elearosterical mechanisms, which combine the electro and sterical interartions, and form stable colloidal dispersions. 

Different ionic monomers were copolymerized with NIPAM or VCL to obtain pH- and T-sensitive miaogels. Snowden et reported the preparation of aqueous microgels by... 

Aqueous microgels were modified by hydroxyapatite (HAp) nanocrystals." During first step, appropriate amount of Ca (N03)2 was dissolved in miaogel dispersion and the pH value has been adjusted to 10 by addition of 25% NH4OH. In a separate flask, appropriate amount of (NH4)2HP04 was... 

The use of aqueous microgels for the preparation of sensitive colloidosomes has been repotted recently by Dinsmore et In this work, temperature-sensitive capsrrles based on poly (N-isopropylactylamide-co-AAc) microgels have be prepared in a W/O inverse emrrlsion. Tire fixation of the microgels in colloidosomes has been achieved by the addition of poly (butadiene-Wocfe-N-methyl 4-vinyl pyridrnirrm iodide). 

In the case of the aqueous microgels, the solubilizing shell is a copolymer containing water-soluble monomers such as methacrylic acid. The major effect in these microgels is from the greatly enlarged volume of the shell... 

In the case of aqueous microgels, this mantle is acrylic polymer containing hydroxyl and carboxyl groups. It is essential that it is joined or grafted to the inner cross-linked core. (Grafting means the linking of one end of a polymer chain to another, as illustrated on p. 164). On neutralization the mantle swells, and because of interactions between particles, imparts non-Newtonian behaviour to the wet coating. 

In summary, we demonstrate that aqueous microgels can be used for growth of HAp nanocrystals (HAp NCs). By using conventional precipitation method the HAp NCs become incorporated into the microgel particles. The... 

Pich A -) Schachschal S Pires PAR —) El Seoud OA Rehage H -) Maas M Reizlein K —) Song A Richtering W — Ketder E von Rybinski W —Kettler E Schachschal S, Pich A, Adler H-J Growth of Hydroxyapatite Nanocrystals in Aqueous Microgels 141... 

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