Hairy particles

Hairy particles can be also prepared by several methods other than graft polymerization, as shown in Figure 12.2.6. This method has advantages in that it can offer a series of hairy particles having the same size core but different lengths and densities of hairs. 

Or, if a proper solvent is chosen, particulate assemblies of block copolymer can be obtained in it. They will be directly cross-linked. The length and density of hairs of particles were adjusted by postreactions. For example, long hairy particles could be converted to crew-cut particles. 

Li D, Dunlap JR, Zhao B (2008) Thermosensitive water-dispersible hairy particle-supported Pd nanoparticles for catalysis of hydrogenation in an aqueous/organic biphasic system. Langmuir 24 5911-5918... 

From Polymers to Colloids Engineering the Dynamic Properties of Hairy Particles... 

Keywords Colloidal dispersions Colloidal glasses Dynamics Grafted particles Hairy particles Micelles Nanoparticle-polymer hybrids Phase diagrams Polymers Rheology Soft colloids- Softness Stars... 

These examples constitute another proof of the reachness of soft hairy particles and the ample possibilities one has to engineer their properties. 

In contrast to the electrostatic stabilization provided by SDS [40,41 ], the nonionic surfactant NP-40 imparts a steric repulsion force between two interactive hairy particles [42, 43]. Stable St mini-emulsions with NP-40 in combination with various coemulsifiers (CA, HD, DMA or SMA) were prepared and characterized [ 13]. The rate of Ostwald ripening for these mini-emulsions decreases in the series CA>DMA>HDsSMA. 

The hairy particles stabilized by non-ionic emulsifier (electrosteric or steric stabilization) enhance the barrier for entering radicals and differ from the polymer particles stabilized by ionic emulsifier [35]. For example, the polymer lattices with the hairy interface have much smaller values of both the radical entry (p) and exit (kdes) rate coefficients as compared to the thin particle surface layer of the same size [128,129]. The decrease of p in the electrosterically stabilized lattices is ascribed to a hairy layer which reduces the diffusion of oligomeric radicals, so that these radicals may be terminated prior to actual entry. For the electrostatically stabilized lattices with the thin interfacial layer, exit of radicals occurs by the chain transfer reaction [35]. This chain transfer reaction results in a monomeric radical which then exits out of the particle by diffusing through the aqueous phase and this event is competing with the propagation reaction in the particle [130]. The decrease of kdes in the electrosterically stabilized latex... 

The ultrasonification process is connected with the rapidly increased oil-water interfacial area as well as the significant re-organization of the droplet clusters or droplet surface layer. This may lead to the formation of additional water-oil interface (inverse micelles) and, thereby, decrease the amount of free emulsifier in the reaction medium. This is supposed to be more pronounced in the systems with non-ionic emulsifier. Furthermore, the high-oil solubility of non-ionic emulsifier and the continuous release of non-micellar emulsifier during polymerization influence the particle nucleation and polymerization kinetics by a complex way. For example, the hairy particles stabilized by non-ionic emulsifier (electrosteric or steric stabilization) enhance the barrier for entering radicals and differ from the polymer particles stabilized by ionic emulsifier. The hydro-phobic non-ionic emulsifier (at high temperature) can act as hydrophobe. 

Zhao el al. have developed an efficient and recyclable hairy particle-sup-ported 4-A,A-dialkylaminopyridine (DAAP) catalyst (393), which is efficient in eatalyzing the MBH reaction of 4-nitrobenzaldehyde and methyl vinyl ketone... 

Hairy Particles 393 (copolymeiized by styrene and VEMPA) — Catalytic site... 

Fujil S, Aono K, Suzaki M, Hamasaki S, S-i Y et al (2012) pH-responsive hairy particles synthesized by dispersion polymerization with a macroinitiator as an inistab and their use as a gas-sensitive liquid marble stabilizer. Macromolecules 45 2863-2873... 

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