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Cool coatings are solar reflective coatings and are applied on roofs, facades, and other exterior surfaces. In this work, the effect of polymer encapsulation was investigated aiming to improve near-infrared (NIR) reflectance of cool coatings. Cool coatings formulated using polymer encapsulated TiO2 resulted in improvement (up to 10%) of NIR reflectance and, therefore, total solar reflectance in comparison to the coatings formulated using bare TiO2, especially in a high pigment volume concentration system.This is mainly due to the TiO2−TiO2 spacing and improved light scattering from the coating films. Enhanced cooling (2.5−11.2 °C) was also observed during heat buildup measurement tests conducted both in the lab under an artificial IR light source and at outdoor conditions under natural light. Refereed/Peer-reviewed

Vesicle-templated polymerization has developed into a mature research area over the last 35 years. The main purpose of this approach was to produce hollow polymeric nanocapsules from low-cost chemicals, utilizing a simple emulsion-polymerization-like process. Over the years, understanding of the different varieties of the approach has grown. In retrospect, the characterization methods utilized to determine the morphologies are essential to draw the right conclusions. In this Review, first, an overview of the earlier attempts to produce nanocapsules with uniformous wall thickness will be given, looking at the results with the current understandings, greatly enhanced by quantification of the different morphologies through cryo-TEM images. The latest approach, reactive oligomer assisted transcriptive synthesis, seems to be able to fulfill the initial purpose and almost 100% of nanocapsule morphologies can be formed under the right conditions.

Poly(alkyl)acrylates are a major class of nonbiodegradable polymers which are difficult to recycle due to an all-carbon backbone. Introducing a certain number of ester bonds in the backbone via rad...

Nonbiodegradable (co)polymers with all-carbon backbone produced via radical polymerization are used in various applications. For some applications, like for example in skincare and haircare, these polymers are nonrecoverable and therefore would be preferably made biodegradable. Therefore, inserting ester bonds in the backbone via radical ring opening terpolymerization of acrylates and 2-methylene-1,3 dioxepane (MDO) could be a suitable approach to obtain biodegradable terpolymers. This report investigates the influence of batch versus semibatch process on the polymerization of three terpolymerization systems viz. (i) methacrylamide (MAAM)/n-butyl acrylate (nBA)/BMDO (5,6-Benzo-2-Methylene-1,3-Dioxepane), (ii) MAAM/nBA/MDO, and (iii) methyl methacrylate (MMA)/VAc (vinyl acetate) /MDO. We demonstrate the improvement in number of ester groups inserted and the homogeneity of insertion via semibatch polymerization processes. The process is guided via optimal monomer addition feeding profiles generated using the reactivity ratios of comonomers. Such improved insertion was demonstrated by the molecular weight distribution of fragments after alkali degradation in the investigated systems.

Anethole, a monomer that can be extracted from bioresources, cannot homopolymerize. Its ability to copolymerize with other vinyl monomers depends on both steric hindrance and the electronic nature of the comonomer. Its copolymerization behaviour with acrylic acid, 2-ethylhexyl acrylate, styrene and methyl methacrylate was investigated. Reactivity ratios were determined by the nonlinear least squares method. Even though the presence of anethole strongly retards the rate of consumption of the comonomer, its incorporation in copolymer chains can be improved with semi batch polymerization. Finally, the side reactions that occur during the copolymerizations – e.g. formation of branches or low molecular weight chains – were investigated. We observed that anethole not only acted as a comonomer, but also as a chain transfer agent, likely due to the presence of labile hydrogen.

Different types of butyl acrylate (BA)-co-acrylic acid (AA) oligomers were synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization and mixed with extruded 200 nm dimethyldioctadecylammonium bromide vesicles. The resulting precursor structures form the basis for subsequent vesicle-templated polymerizations. Systematic variations in temperature, pH, oligomer length, and oligomer composition and their effects on precursor morphology were studied. Surprisingly, different morphologies were obtained, including capsules, protruded capsules, solid spheres, and multicompartment structures. For example, capsules and multicompartment structures were found to result from higher AA contents, and protruded capsules and solid particles resulted from lower AA contents. Subsequent chain extension of the RAFT oligomers resulted in polymer nanostructures resembling the precursor morphologies.

A range of copolymers of methacrylic acid (MAA) macromonomers prepared by cobalt-catalyzed chain transfer and methyl methacrylate (MMA) and/or butyl acrylate (BA) was synthesized and used as a stabilizer in the emulsion polymerization of MMA. Although clear differences were observed in polymerization rates using the different MAAx-MMAy stabilizers, these differences were not as clearly reflected in the particle sizes nor in the rates per particle. However, a clear difference between these systems and those stabilized by MAAx-BAy was observed. The latter systems were all characterized by much smaller particle sizes and corresponding higher rates of polymerization. In addition, the molar masses in the latter systems were all significantly larger than those obtained in the MAAx-MMAy stabilized system, in which the stabilizers act as "sulfur-free" RAFT agents. Interestingly, the prepared latexes showed a range of appearances varying from "milky" to "gel-like" depending on the used stabilizer. The MAAx-BAy stabilized latexes had, in general, a lower viscosity and a significantly smaller (if any) yield stress than the MAAx-MMAy stabilized latexes, and in the latter case the rheological behavior was found to depend on the block lengths in and concentration of the stabilizer.

Recycling and biodegradability of chain-growth polymers is an important and growing topic. Introducing ester bonds in polymers via cyclic ketene acetals (CKAs) is an interesting route to create (bi...

Degradable analogues of polystyrene are synthesized via radical ring-opening (co)polymerization (rROP) between styrene and two cyclic ketene acetals, namely 2-methylene-1,3-dioxepane (MDO) and 5,6-benzo-2-methylene-1,3-dioxepane (BMDO). This approach periodically inserts ester bonds throughout the main chain of polystyrene, imparting a degradation pathway via ester hydrolysis. We discuss the historical record of this approach, with careful attention paid to the conflicting findings previously reported. We have found a common 1H NMR characterization error, repeated throughout the existing body of work. This misinterpretation is responsible for the discrepancies within the cyclic ketene acetal (CKA)-based degradable polystyrene literature. These inconsistencies, for the first time, are now understood and resolved through optimization of the polymerization conditions, and detailed characterization of the degradable copolymers and their corresponding oligomers after hydrolytic degradation.

A thorough experimental investigation of polymer-glass transition temperature (T

A thorough experimental investigation of polymer-glass transition temperature (Tg ) is performed on poly(vinyl alcohol) (PVA) and fumed silica nanoparticle (SiNP) composite. This is done together with atomistic molecular dynamics simulations of PVA systems in contact with bare and fully hydroxylated silica. Experimentally, PVA-SiNP composites are prepared by simple solution casting from aqueous solutions followed by its characterization using Fourier-transform infrared spectroscopy (FTIR), dynamic mechanical analysis (DMA), and dynamic scanning calorimetry (DSC). Both theoretical and experimentally deduced Tg are correlated with the presence of hydrogen bonding interactions involving OH functionality present on the surface of SiNP and along PVA polymer backbone. Further deconvolution of FTIR data show that inter-molecular hydrogen bonding present between PVA and SiNP surface is directly responsible for the increase in Tg . SiNP filler and PVA matrix ratio is also optimized for a desired Tg increase. An optimal loading of SiNP exists, in order to yield the maximum Tg increase arising from the competition between hydrogen bonding and crowding effect of SiNP.

Commercially available azo dyes bearing amino groups were grafted to zwitterionic copolymers composed of cyclic anhydride functionality. The zwitterionic copolymers were prepared for the first time by polymerizing sulfobetaine (SB) monomer with maleic anhydride (MA) under conventional free radical polymerization as well as reversible addition-fragmentation chain transfer (RAFT) polymerization. Poly(SB- co-MA) self-assembled in deionized water. Azobenzene grafted zwitterionic poly((SB- co-MA)- g-Azo) exhibited multiresponsive behavior. As confirmed by UV-vis spectroscopy, trans → cis isomerization of the azo group was responsible for the photo- and thermal responsive behavior. The photoisomerization was reversible, and no photoaging was detected during the repeated exposure to UV and visible light. The water-soluble nature of photoresponsive azo dye grafted copolymers makes it suitable for applications in biological systems.

Vesicle templated emulsion polymerization is a special form of emulsion polymerization where the polymer is grown from the outside of the vesicle, leading to nanocapsules. Cost effective nanocapsules synthesis is in high demand due to phasing out of older methods for capsule synthesis. Although the first indications of this route being successful were published some 10 years ago, until now a thorough understanding of the parameters controlling the morphologies resulting from the template emulsion polymerization was lacking. Most often a mixture of different morphologies was obtained, ranging from solid particles to pro-trusion structures to nanocapsules. A high yield of nanocapsules was not achieved until now. In this paper, the influence of initial vesicle dispersion, choice of the Reversible Addition-Fragmentation chain Transfer (RAFT) species and oligomer, monomer and crosslinker have been investigated. It turns out that good initial vesicle dispersion, molecular control of the RAFT process, a not too hydrophobic monomer and some crosslinking is needed to result in high yield of nanocapsules. In previous work, the level of RAFT control was often suboptimal and not properly verified and although nanocapsules were shown, other morphologies were also present. We now believe we have a full understanding of vesicle templated nanocapsules synthesis, relevant to many applications.

Polymer encapsulation of clay platelets through (mini)emulsion polymerization can be a versatile method to obtain hybrid nanoparticles with several important applications. However, to achieve actual encapsulation of the single clay platelets inside latex particles is relatively difficult. For single clay platelet encapsulation, complete exfoliation and colloidal stability needs to be achieved as well as kinetic and/or thermodynamic control mechanisms to locate and maintain the position of the single clay platelet on the inside of the latex particle. An overview of these mechanisms will be given and an overview of the most relevant attempts in this area will be discussed in retrospect in the context of a systematic mechanistic understanding.

NaI-catalyzed reversible complexation mediated living radical polymerization (RCMP) was combined with polymerization induced self-assembly (PISA) to generate self-assemblies. Poly(methacrylic acid) (PMAA) and poly(methyl methacrylate) (PMMA) were used as hydrophilic and hydrophobic segments, respectively, to generate self-assemblies. Micelles (nano-particles), worms (nano-cylinders), and vesicles (nano-capsules) were generated in ethanol at 5–9 wt% solid content. The self-assemblies were also fixed (crosslinked) by using a cross-linkable divinyl monomer, i.e., ethylene glycol dimethacrylate (EGDMA), as a comonomer in the hydrophobic segment. NaI-catalyzed RCMP is a heavy-metal-free and sulfur-free synthetic method. The nano-particles, cylinders, and capsules obtained through the RCMP/PISA process are highly attractive for biomedical, healthcare, cosmetics, and agrochemical release applications. ASTAR (Agency for Sci., Tech. and Research, S’pore)

The differences between internal and external plasticization as well as how the molecular structure of a plasticizer effects the glass transition temperature, Tg, of a (meth)acrylate terpolymer is analyzed with molecular dynamics (MD) simulations and measured with differential scanning calorimetry (DSC). 1-phenoxy-2-propanol (PPH), butyl carbitol (BC) and ethylene glycol-2-ethylhexyl ether (EEH) are added either as free external plasticizers or are integrated into the polymer as internal bonded plasticizers. The simulation model is validated by finding excellent agreement of predicted Tg-values of various relevant homopolymers and terpolymers with measured values and values that are derived from established empirical equations. Simulation results suggest an aggregation of polymer alkyl groups into non-polar nano-domains. Moreover, addition of the three external plasticizers lowers Tg substantially. This Tg-loss is partially recovered after directly integrating the free plasticizers into the polymer. Bulkier plasticizers, such as BC, are more effective internal plasticizers because their larger size increase the distance between polymer chains to a larger extend, which leads to weaker average interactions among the chains, thereby reducing Tg. On the other hand, more compact free plasticizers, such as PPH, exhibit a lower diffusive energy barrier that causes more frequent diffusive moves. This stimulates the diffusive movement also of the polymer, which reduces Tg. Hence, integrating such a compact plasticizer into the polymer leads to a larger recovery of the Tg - loss that was induced by its free form. Overall, the complementary use of MD simulations and DSC measurements provide insights on the differences on how internal and external plasticizers influence Tg, respectively, and identifies the underlying molecular causes. External plasticization reduces Tg more effectively than internal plasticization. Hence, a drop in Tg caused by an external plasticizer can be partially recovered by integrating the plasticizer into the polymer. A possible application is the design of reactive coalescing agents for coatings that bind to the polymer after application and that could replace conventional and potentially harmful coalescing agents that evaporate into the environment.

Modeling of Emulsion polymerization processes is based on the knowledge of fundamental kinetic and thermodynamic parameters. The most important kinetic parameters are propagation and termination rate coefficients. Ten years ago a paper has been published with the title “Modeling of Emulsion Polymerization, will it ever be possible?”. The paper expresses serious doubts whether the different kinetic parameters will ever be available for general industrial recipes containing several monomers. In this paper the developments in the last 10 years regarding pulsed initiation polymerization (PIP) and other techniques regarding the determination of especially the kinetic parameters will be discussed. Amongst the areas where progress can be seen is the understanding of acrylate systems and water soluble monomers. New techniques like MALDI-ToF MS and time resolved electron spin resonance have strongly contributed to the area. Also the puzzling effect of chain length dependent propagation is discussed. Finally an answer will be given to the title question.

Binding of cations to chondroitin sulfate A and C, Chondroitin, and D-glucuronate was investigated in neutral and acidic aqueous media using H+, Cu2+, and Na+ ion-specific electrodes, viscometry, electron spin resonance (esr), and ligand-field spectroscopy. Site binding to the carboxylate group and only electrostatic interaction with the sulfate group could describe the results well. The nitrogen atom of the N-acetyl group appeared not to be involved in bonding of cations to chondroitin(sulfate) systems. The interaction of the divalent metal ions follows the Irving-Williams series. The value of the electrostatic potential at the carboxylate group of chondroitin(sulfate), as experienced by a cation, was determined in dependence of cation bonding. It proved to be difficult to establish the composition of a complex of a metal ion with a polyion by means of a molar ratio curve.

Rate constants for the reaction of aquanitrocobaloxime with thiourea were measured as a function of pH, solvent composition, pressure and temperature, in dioxane-water mixtures. With the aid of solubility measurements a complete quantitative analysis of solvent effects on the initial state and transition state transfer parameters could be made. It was found that the activation enthalpy and entropy vary strongly with solvent composition. This is in contrast to the variations found for vitamin B12, for which this cobaloxime is a model compound. The rate constants increase strongly after 50 vol.% dioxane in the dioxane-water mixtures, another difference with vitamin B12. The volumes of activation are small and positive, in accordance with a dissociative mode of activation.

The rate constants for the reaction of aquocobalamin with thiosulphate were measured as a function of ionic strength and solvent composition in dioxane-water mixtures.

The rate constants for the reaction of aquocobalamin with the thiocyanate ion were measured as a function of ionic strength and solvent composition in acetonitrile-water mixtures. The reaction is described by a two-step mechanism: the ligation reaction, where the most stable isomer (S-bonded) is formed and the isomerisation reaction (S-bonded to N-bonded thiocyanate). For the ligation reaction a full quantitative analysis of solvent effects could be performed, whereas for the isomerisation reaction only qualitative observations were made. The equilibrium constant for the isomerisation (S-bonded/N-bonded) is large and does not change with the solvent composition. It is found that the transfer Gibbs energies of activation for the ligation reaction are the same as found for the ligand thiourea. The absence of a solvent effect on the isomerisation reaction is a further example of the ability of vitamin B 12 to create its own micro environment.

Apparent molar volumes φ v , were measured at 25 °C in 0.1 molal NaClO 4 for aquocobalamin chloride, methylcobalamin, 5′-deoxyadenosylcobalamin and aquanitrocobaloxime. For the organocobalamins the pH dependence of φ v was studied, and for aquocobalamin and aquanitrocobaloxime the dependence on solvent composition was studied. The base-off forms of the organocobalamins have the same volumes as the base-on forms. The apparent molar volume of aquocobalamin chloride is almost independent of solvent composition in dioxane-water mixtures, but increases dramatically in acetonitrile-water mixtures.

The solubilities of aquocobalamin chloride and eight other cobalt(III) complexes have been measured in dioxane–water mixtures. For aquocobalamin chloride, aquanitrocobaloxime and aquamethylcobaloxime solubilities have also been measured as a function of temperature. The transfer thermodynamic functions ∂mG°, ∂mH° and ∂mS° have been calculated. The results may be accounted for in terms of the cavity energy and specific interactions. A difference has been found between the transfer functions of the aquocobalamin cation in dioxane–water mixtures and those in acetonitrile–water mixtures.