Thermosetting acrylic latexes were synthesized using butyl acrylate (BA), methyl methacrylate (MMA), 2-hydroxyethyl methacrylate (HEMA), and methacrylic acid (MAA) via seeded two-stage process. A 2-level factorial experimental design was employed to investigate the effect of hydroxyl (core phase), carboxylate (shell phase) groups, and type of surfactant (Triton X200, Tergitol XJ) on the mechanical properties of thermosetting latexes. Eight latexes with varying concentration of HEMA, MAA and two types of surfactants were synthesized and crosslinked with three crosslinkers. Latex functionality for crosslinking was located in the core only, the shell only, and both the core–shell with varying concentrations. Melamine-formaldehyde (hexamethoxymethyl melamine) resin was employed to crosslink hydroxyl functionalities in the core. Carboxylic acid groups in the shell were crosslinked with zinc ammonium carbonate. HDI isocyanurate (Desmodur N3300A) were used to crosslink with hydroxyl or carboxyl functional groups in core and shell. The mechanical properties of coatings were evaluated in terms of tensile properties, cross-hatch adhesion, pencil hardness, and impact resistance. Design of experiment (DOE) was utilized to investigate the effect of variables on mechanical properties of crosslinked thermoset films.

Two methods were used to prepare polysiloxane-functionalized acrylic latexes via emulsion polymerization. Ethyl acrylate and 2-ethylhexyl acrylate were used in both methods as acrylic phase. In the first method, an acrylic core was prepared with addition of a coupling agent, 3-(trimethoxysilyl) propyl methacrylate, after which cyclic siloxane monomer (octamethylcyclotetrasiloxane) was reacted with the coupling agent. In the second method, a silane-terminated polysiloxane (H-PDMS) was reacted with ethylene glycol dimethacrylate, and then copolymerized with ethyl acrylate and 2-ethylhexyl acrylate in a batch emulsion polymerization. Particle size distribution and particle morphology were evaluated by using dynamic light scattering (DLS) and transmission electron microscopy (TEM), respectively. Core-shell morphology was observed in TEM for the first preparation method as proposed. After film formation, surface tension, morphology and dynamic mechanical properties were investigated. Stratification of polysiloxane was examined by Fourier-transform infrared spectroscopy (FT-IR) and energy dispersive X-ray (EDX). Energy dispersive X-ray data indicated that only the second preparation method had higher silicon content at film-air interface than film-substrate interface. In both methods, storage modulus and surface energy of latex films decreased after grafting polysiloxane.

A series of amphiphilic poly(2-hydroxyethyl methacrylate)-b-polydimethylsiloxane-b-poly(2-hydroxyethyl methacrylate) (pHEMA-b-PDMS-b-pHEMA) (A-B-A) triblock copolymers were synthesized from three different carbinol-terminated polydimethylsiloxanes with varying molecular weight. A carbinol-terminated polydimethylsiloxane was modified with 2-bromoisobutyryl bromide to obtain a macroinitiator. The block copolymers were characterized by NMR, GPC, and dynamic light scattering (DLS). Reverse micelles of a copolymer were formed in mixture of benzene/methanol solution which served as nanoreactors for the synthesis of magnesium fluoride (MgF2) nanoparticles. The MgF2 was prepared via chemical precipitation using magnesium chloride and potassium fluoride as reactants. The MgF2-triblock copolymer composites were synthesized as a function of MgF2weight ratio (0.5, 5, and 10 wt%) in copolymer. The MgF2 colloids were dissolved in three organic solvents: methanol, isopropanol, and tetrahydrofuran. The polymer nanoparticles were characterized by DLS, transmission electron microscopy, thermogravimetric analysis, and X-ray diffraction (XRD) analysis. The formation of MgF2 crystals was observed by XRD. Particle size and particle size distribution showed significant changes in different solvents. The thermal stability of MgF2 colloids increased as the amount of nanoparticle increased in polymeric matrix. (c) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

A series of amphiphilic poly(2-hydroxyethyl methacrylate)-b-polydimethylsiloxane-b-poly(2-hydroxyethyl methacrylate) (pHEMA-b-PDMS-b-pHEMA) (A-B-A) triblock copolymers were synthesized with varying block molecular weights. Control over the polymerization, micellar size and size distribution, dynamic mechanical properties, and film morphology of nine triblock copolymers was investigated as a function of block length. The polymerization resulted in copolymers with polydispersity index below 1.5. The self-assembly behavior of the triblock copolymers was studied in selective solvents for A and B blocks. The micellar diameter was determined by dynamic light scattering and transmission electron microscopy. The film morphologies were investigated by small angle X-ray scattering. Phase separation was observed when the blocks had similar molecular weights (symmetry). However, the ordering of the morphology was disrupted when the blocks lengths were asymmetric. Phase separation was observed by atomic force microscopy when the block molecular weights were symmetric. The viscoelastic properties were examined using dynamic mechanical analysis. The modulus and crosslink density increased with increasing pHEMA content. Number of aggregations is very small when THF was used compared with methanol and methanol–water. Aggregation of copolymers was difficult in THF due to back-folding and looping of PDMS block. This was unfavorable as it increases free energy of system. This probably resulted in higher CMC of pHEMA-b-PDMS-b-pHEMA copolymers in THF than in methanol. Micellar size of most of triblock copolymers in THF was smaller than in methanol.

Three methods were used to prepare polysiloxane-functionalized acrylic latexes via emulsion polymerization. Ethyl acrylate and 2-ethylhexyl acrylate were used in all three methods as the acrylic phase. In the first method, an acrylic core was prepared with addition of a coupling agent, 3-(trimethoxysilyl) propyl methacrylate, after which a cyclic siloxane monomer (octamethylcyclotetrasiloxane) was reacted with the coupling agent. In the second method, a silane-terminated polysiloxane (H-PDMS) was reacted with ethylene glycol dimethacrylate, and then copolymerized with ethyl acrylate and 2-ethylhexyl acrylate in a batch emulsion polymerization. In the third method, cyclic siloxane monomer was added during emulsion polymerization of ethyl acrylate, 2-ethylhexyl acrylate, and 2-hydroxyethyl methacrylate. Particle size distribution and particle morphology were evaluated using dynamic light scattering (DLS) and transmission electron microscopy (TEM), respectively. A core-shell morphology was observed in TEM for the first preparation method as proposed. After film formation, surface tension, morphology and dynamic mechanical properties were investigated. Stratification was also examined by Fourier-transform infrared spectroscopy (FT-IR) and energy dispersive X-ray (EDX). Microphase separation was observed by atomic force microscopy (AFM) after polysiloxane modification. Energy dispersive X-ray data indicated that only the second preparation method had a higher silicon content at the film-air interface than film-substrate interface. In all methods, the storage modulus and surface energy of latex films decreased after polysiloxane modification.

A dual-cure latex is prepared by mixing an amide-functionalized latex with a latex that has both acetoacetoxy and unsaturated acrylic functionalities. The amide-functionalized latex provides a thermal cure with the acetoacetoxy groups of the other latex via Michael addition. The partially polymerized triacrylates in the acrylate-functionalized latex provide active sites for photocuring. Thermoset latex films are prepared by blending amide- and acrylate-functionalized latexes in varying amounts. The effect of the photosensitizer (camphorquinone) concentration on thermal and mechanical properties is studied. The highest tensile modulus and elongation is observed in a 50:50 wt% amide/acrylate-functionalized latex blend.