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Recent Advances and Future Perspectives in Heterophase Polymerization
Published in Hugo Hernandez, Klaus Tauer, Heterophase Polymerization, 2021
The stability ofminiemulsions is usually improved by hydrophobic compounds (e.g., hexadecane) sometimes in an incorrect way (cf. below, p. 47) also denoted as co-stabilizers. Even though they are not surfactants, they help improve the stability of the miniemulsion, particularly against Ostwald ripening. Thus, Asua [46] proposed that the concept of reactive surfactants can also be extended to reactive co-stabilizers, (i.e., hydrophobic monomers, initiators, or chain transfer agents), thus ensuring incorporation of those compounds into the polymer and avoiding unwanted side effects such as residual emissions of volatile organic compounds (VOCs) or reduced performance. He found that an optimal reactivity of the co-stabilizer is required for each miniemulsion system, in order to achieve good stability without degrading the final performance of the product.
Fluid–Fluid Dispersions: Liquid–Liquid and Gas–Liquid Systems
Published in Wioletta Podgórska, Multiphase Particulate Systems in Turbulent Flows, 2019
Polymeric surfactants are macromolecules in which the amphiphatic character is brought about either by hydrophilic and hydrophobic polymeric sequences with a sufficient number of repeat units, or by hydrophilic and hydrophobic units randomly spread within the chain. They are used as an alternative to ionic surfactants that are sensitive to the presence of electrolytes, and nonionics that may tolerate high electrolyte concentration, but are seldom strongly adsorbed. Polymeric surfactants are often used in miniemulsion polymerization. Although some polymeric surfactants have lower interfacial properties than low molecular weight surfactants, they are convenient stabilizers, because the first step in emulsification is carried out by a high energy process, so the key point is the ability of surface-active polymers to prevent coalescence during the emulsification step by providing steric repulsion. Surface-active polymers are also often used in combination with low molecular weight surfactants. In this case, low molecular weight surfactants act as emulsifiers and polymeric surfactants, which do not diffuse rapidly to newly created interfaces but adsorb very strongly, acting as stabilizers. An example of a polymeric surfactant is PVA, which is partially hydrolyzed poly(vinyl acetate). This polymer has been widely used in many fields for years (Tadros et al., 2004; Tadros, 2006, 2009).
Acrylic Adhesives
Published in István Benedek, Mikhail M. Feldstein, Technology of Pressure-Sensitive Adhesives and Products, 2008
In a miniemulsion polymerization the reaction mixture is sonicated with high energy to reduce the monomer droplet size to 50–500 nm. Stabilization is achieved with an emulsifier, used below the CMC to avoid micellar nucleation, in combination with a hydrophobic cosurfactant such as a long-chain alkane. A hydrophobic comonomer such as stearyl methacrylate can also serve this purpose. A number of benefits have been cited for the miniemulsion process. One benefit is that particle size can be controlled by the intensity and duration of sonication. There is little subsequent mass transfer between particles due to the low water solubility of the cosurfactant. Hence, the size distribution can be maintained throughout the process. The rate of monomer conversion is much more rapid than in conventional (macro)emulsion polymerization. A further advantage is that the miniemulsion process affords the possibility of more control over molecular weight distribution. A detailed review of miniemulsion polymerization has been given by Asua [116].
Molecularly imprinted nanoparticles with recognition properties towards diphtheria toxin for ELISA applications
Published in Journal of Biomaterials Science, Polymer Edition, 2023
Süleyman Serdar Alkanlı, Fulya Dal Yöntem, Merve Yaşar, Celal Güven, M. Vezir Kahraman, Nilhan Kayaman Apohan, Zerrin Aktaş, Mustafa Oral Öncül, Ayhan Ünlü, Handan Akçakaya
There are two main problems encountered in the preparation of biomacromolecule imprinted materials. The first is the denaturation of proteins or peptides during the imprinting process. To avoid this problem, the reactions and imprinting process must be carried out under physiological conditions (neutral pH, aqueous medium and room temperature) [31]. The second problem is slow mass transfer. Although molecular imprinting has recently been used for biomacromolecular targets such as peptides and proteins, imprinting problems have not been completely overcome [31–33]. Therefore, there is an increasing interest for epitope imprinting approach in current studies. Shea et al. used a plastic antibody against the bee venom mellitin (26 amino acids) to treat mice infected with mellitin for the first time, adding a new dimension to molecular imprinting applications [34]. Our template molecule is DT (535 amino acids), which has a much larger molecular weight than mellitin. In another study using epitope imprinting, boronate affinity-anchored epitopes used as a template for imprinting of β2-Microglobulin (B2M) containing 99 amino acids and myoglobin (Mb) containing 153 amino acids [12]. Other researchers have immobilized hemoglobin (Hb) on silica nanoparticles and then fragmented by trypsin digestion. HB-selective MIPs was synthesized by imprinting the peptides obtained by washing after digestion [10]. In our study, we preferred the miniemulsion polymerization technique by the surface imprinting method. The main reason for this choice is the miniemulsion technique is that it eliminates the problems of other conventional emulsion polymerizations such as water dissolution and transport of reactants through the aqueous phase. Moreover, during the miniemulsion polymerization reaction time, under ideal conditions, the monomer drops are small in size, homogeneous and kinetically stable.
Preparation and evaluation of polymer-encapsulated UV filter nanocapsules with miniemulsion polymerization
Published in Journal of Dispersion Science and Technology, 2021
Qing An, Xinjiong Ni, Dong Liu, Yun Zhang, Yuhua Cao
Besides absorbance and reflection of UV radiation by UV filter microcapsules, nanocapsules at submicron level can scatter sunlight. The scattering light intensity is reversely proportional to the fourth power of the wavelength. So, the short wavelength of UVC and UVB are scattered to the larger extent. Miniemulsion polymerization is an appropriate approach to synthesize polymer-encapsulated organic UV filter at submicron size. The miniemulsion is composed of submicron (50–500 nm) oil droplets dispersed in aqueous phase stabilized with an emulsifier. Each droplet serves as a microreactor, where miniemulsion polymerization occurs to obtain submicron polymer particles.[24,25] The size and monodispersity of the nanoparticles largely depend on the emulsifier and its concentration. In general, the concentration of the emulsifier is slightly smaller than its CMC to avoid micellar nucleation. As can be seen, as SDS concentration was 1–3 (wt%), much larger than CMC, the size of PMMA encapsulated UV filter ethylhexyl salicylate (EHS) was at micrometer level.[6] The SPF improved by 40% compared with free EHS. A miniemulsion polymerization was used to synthesize nanocapsules to encapsulate octocrylene (OCT) with EGDMA as the monomer, PVA as the emulsifier.[26] The average diameter of the nanocapsules was 318 nm, and the SPF increased by 100% compared with free OCT. A miniemulsion assembly of nanocapsules encapsulating hydrophobic organic and inorganic sunscreen filters with an amphiphilic block copolymer polystyrene-block-polyethylene glycol (PS-b-PEG) was reported.[16] Using both organic and inorganic filter, as well as polystyrene (PS) as the core material, the nanocapsules with sizes from 80 to 200 nm had broad-spectrum and high sun protection ability.