Special Issue on “Multifunctional Hybrid Materials Based on Polymers: Design and Performance”

Hybrids and composite materials offer a synergic combination of polymer and inorganic features [...

Special Issue on “Function of Polymers in Encapsulation Process”

Encapsulation technology comprises enclosing active agents (core materials) within a homogeneous/heterogeneous matrix (wall material) at the micro/nano scale. In the last few years encapsulation has gained a lot of interest. Using this process, a physical barrier is developed between the inner substance and the environment which on one hand prevents its degradation and facilitates its handling and transportation and on the other hand allows the controlled release of the core material in a certain ambiance [1]. Polymers may be used to trap the material of interest inside the micro/nano-capsules. Such encapsulated systems have many applications in the fields of the food industry, drug delivery, agriculture, cosmetics, coatings, adhesives and so forth. Various biopolymers, such as alginate, chitosan, carrageenan, gums, gelatin, whey protein or starch, act as a barrier against external conditions. Encapsulation in biodegradable polymers can also enhance the permeability and stability of the active agent and thus its bioavailability. Choosing the right polymer is very important in this process due to its impact on target delivery and controlled release, and therefore, on the bioavailability of active agents. It should have the necessary properties, such as being non-reactive with the active agent, flexibility, stability, strength, and impermeability. If the active agent has application in the food industry, the used polymer should be “generally recognized as safe” (GRAS), biodegradable, and capable of preserving the encapsulated material from the atmospher

Experimental validation of a mathematical model for the evolution of the particle morphology of waterborne polymer-polymer hybrids: paving the way to the design and implementation of optimal polymerization strategies

Polymer-polymer composite nanoparticles allow both the improvement of the performance in stablished applications of waterborne polymer dispersions and targeting new applications that are out of reach of currently available products. The performance of these materials is determined by the particle morphology. To open the way to process optimization and on-line control of the particle morphology, the capability of the recently developed model to predict the evolution of the particle morphology during seeded semibatch emulsion polymerization process was evaluated. Structured polymer particles were synthesized by copolymerization of styrene and butyl acrylate (St-BA) on methyl methacrylate and butyl acrylate (MMA–BA) copolymer seeds of different Tgs. The model captured well the effect of process variables on the evolution of the particle morphology, opening the way to the design and implementation of optimal strategies.The financial support of the RECOBA project (funding from European Framework Horizon 2020, No. 636820) is gratefully acknowledged

Turbidity spectroscopy as a potential tool to online monitor emulsion polymerization processes

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Kinetics of the Aqueous Phase Copolymerization of MAA and PEGMA Macromonomer: Influence of Monomer Concentration and Side Chain Length of PEGMA

An in situ nuclear magnetic resonance spectroscopy (NMR) technique is used to monitor the aqueous-phase copolymerization kinetics of methacrylic acid (MAA) and poly(ethylene glycol) methyl ether methacrylate (PEGMA) macromonomers. In particular, the study analyses the effect of the number of ethylene glycol (EG) groups along the lateral chains of PEGMA and is carried out under fully ionized conditions of MAA at different initial monomer ratios and initial overall monomer concentrations (5-20 wt % in aqueous solution). The composition drift with conversion indicates that PEGMA macromonomer is more reactive than MAA. Individual monomer consumption rates show that the rates of consumption of both monomers are not first order with respect to overall concentration of the monomer. The reactivity ratios estimated from the copolymerization kinetics reveal, that for the short PEGMA, the reactivity ratios r(MAA) and r(PEGMA) increase with the solids content (SC). A totally different trend is obtained for the longer PEGMA, whose reactivity ratio (r(PEGMA23)) decreases with solids content, whereas the reactivity ratio of MAA remains roughly constant.This work has been carried out in the framework of the BASKRETE initiative under the umbrella of the EUSKAMPUS project. Iraki Emaldi acknowledges the funding provided by EUSKAMPUS Fundazioa, POLYMAT and TECANLIA for his scholarship. Shaghayegh Hamzehlou and Jose Ramon Leiza acknowledge the funding provided by MINECO (CTQ 2014-59016P) and Basque Government (IT-999-16). Jorge Sanchez Dolado acknowledges the funding for the GEI Green Concrete Project given by the Basque Government (2015 Emaitek Program). The authors also thank the discussion with Jose arlos de la Cal on the estimation of the reactivity ratios and they are grateful to Jose nacio Miranda and the SGIker Gipuzkoa Unit (UPV/EHU) for the NMR facilities

Acidic Aqueous-Phase Copolymerization of AA and HPEG Macromonomer: Influence of Monomer Concentration on Reactivity Ratios

Poly(acrylic acid-co-polyethylene glycol 2-methyl-2-propenyl ether) copolymers are comb-like water-soluble copolymers produced by the copolymerization of acrylic acid (AA) and polyethylene glycol 2-methyl-2-propenyl ether (HPEG). The main application of these copolymers is as superplasticizers for cementitious materials, also known as polycarboxylate ethers (PCE's). The kinetics of the water-soluble monomers is substantially more complex than that of non-water-soluble monomers as their kinetics depend on various parameters such as monomer concentration, pH, and ionic strength. In this work, aqueous in situ H-1 NMR copolymerizations of AA and HPEG at different initial overall monomer weight fractions and comonomer molar ratios under acidic media were carried out. The gathered kinetic data were used for the estimation of the reactivity ratios of AA-HPEG. A nonlinear least-squares (NLLSQ) method based on the Mayo-Lewis composition equation was used to estimate the reactivity ratios by fitting the cumulative copolymer composition or free monomer molar fraction as a function of overall monomer conversion. The estimation indicates that the reactivity ratio of acrylic acid is higher than that of the HPEG monomer, which is estimated as close to zero. In addition, the reactivity ratio of AA depends on the overall monomer weight fraction; the higher the initial overall monomer concentration, the higher the reactivity ratio is. An empirical expression is derived that describes the dependency of the reactivity ratio of AA on the overall monomer mass fraction (r(AA) = 1.76 (+/- 0.062) + 0.0275 (+/- 4.37 x 10(-3)) w(M) (%); r(HPEG) = 2.3 x 10(-14) (+/- 6.02 x 10(-3))).This work has been carried out with the funding provided by CHRYSO, SAINT-GOBAIN Construction Chemicals. S.H. and J.R.L. acknowledge the Basque Government (grant IT-1521-22) and Spanish Government (MINECO PID2021-123146OB-I00)

Shedding light on the microstructural differences of polymer latexes synthesized from bio-based and oil-based C8 acrylate isomers

There is a great interest in replacing traditional oil-based monomers with more renewable bio-based ones. However, their replacement in current formulations is not straightforward. Herein, we investigate the origin of the microstructural differences of the homopolymers of 2-octyl acrylate (2-OA, bio-based) and its isomer 2-ethylhexyl acrylate (2-EHA, oil-based) synthesized by emulsion polymerization through Density Functional Theory calculations (DFT) and a kinetic Monte Carlo study. DFT calculations show that hydrogen abstraction from the polymer backbone in 2-EHA homopolymer is predominant comparing to the chain transfer to polymer reaction in the side chain, while this trend is inverse for 2-OA homopolymer. The Monte Carlo model is able to fit well the experimental data of both homopolymerizations, and predicts the microstructural differences between the two systems, namely; higher amount of gel and molar mass of the gel in 2-OA homopolymerization.he authors would like to thank the financial support received from the Basque Government (IT-1525-22), from the Spanish Government (MINECO PID2021-123146OB-I00, MICINN PDC2021-121416-I00 and PID-117628RJ-I00))

Modelling and control of the microstructure of MAA-co-PEGMA water soluble copolymers

Water soluble poly(MAA-co-PEGMA) copolymers present comb like structure, where the size of the lateral chain can be tuned by using PEGMA macromonomer of different number of ethylene glycol units. This type of macromolecules under alkali conditions present an anionic backbone due to the ionization of the carboxylic monomers, and uncharged side chains. This type of copolymers are widely used in construction as superplasticizers for cementitious formulations. It is known that several parameters such as the molar mass, lateral chain length and sequence distribution of the monomers in the chains have a tremendous impact on the performance of the copolymers when applied as superplasticizers. Therefore, obtaining copolymers with a controlled microstructure is required to be able to understand their interaction with the cementitious formulations. Starved semibatch free radical copolymerization has been widely employed to control the chemical comonomer composition in both solution and emulsion polymerization. Despite of the good control on the composition, long addition times are required. Thus, the modelling of the addition policies is necessary in order to shorten the reaction times ensuring a homogenous composition and control of the molecular weight distribution through the whole reaction. The kinetics of the water soluble monomers are substantially more complex than non-water soluble ones, as their kinetics depend on various parameters such as monomer concentration, pH and ionic strength 1, 2. The knowledge of kinetics parameters and their dependency on different variable is the key parameter to develop a predictive mathematical model. In the current work, a detailed mathematical model was developed to predict the microstructure of the copolymers considering all the complexities of the kinetics of water soluble monomers. Batch solution copolymerization reactions (using jacketed reactors and in situ NMR) and semibatch experiments were carried out with different feeding ratios at temperatures ranging from 70 to 90 ºC and with the carboxylic monomer at fully ionized conditions. The kinetic parameters, namely reactivity ratios3 and propagation rate coefficients were estimated using experimental data of conversion, molecular weight as well as copolymer composition. Furthermore, the mathematical model was used to develop advance control strategies in a reaction calorimeter for the control of the microstructure of these copolymers. 1. Lacík, I.; Ucnová, L.; Kukućkova, S.; Buback, M.; Hesse, P.; Beuermann, S. Macromolecules. 2009, 42, 7753-7761. 2. Smolne, S.; Weber, S.; Buback, M. Macromol. Chem. Phys. 2016, 217, 2391-2401. 3. Emaldi, I.; Hamzehlou, S.; Leiza, Dolado, J.S.; Leiza, J.R. Processes. 2017, 5, 19

Modeling and characterization of the morphology of multiphase polymeric nanoparticles

Multiphase polymeric nanoparticles that synergistically combine the properties of their constituents present enhanced properties and display new functionalities. Therefore, they are used in a wide range of applications including anticorrosive, superhydrophobic and anti-molding coatings; switchable adhesives; photoswitchable fluorescent particles; energy storage; gene and drug delivery; anticounterfeiting and LEDs. Although it is recognized that application properties strongly depend on the morphology of the nanoparticles, there is a surprising lack of progress towards the knowledge-based synthesis of these materials with well controlled morphologies. There are two main reasons for this. Firstly, the difficulties associated to the accurate characterization of the morphology of the polymeric nanoparticles, and secondly, the lack of quantitative understanding of the processes controlling the morphology. Please click Additional Files below to see the full abstrac

Inline and offline particle size analysis in emulsion polymerization processes

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