Water-soluble Comonomers Research Articles

Effect of surfactant concentration and monomer polarity on particle nucleation in emulsion step polymerization of dithiol with diene

The dependence of the number of particles Np as a function of the surfactant concentration [S] is investigated for the step polymerization of dithiol-diene emulsions. A sigmoidal curve for log Np vs log [S] is found for a range of monomers regardless of their polarity. Above the critical micellar concentration (6–20 mM), a Np ∝ [S]x relationship is established with an exponent x dependent on the polarity of the two co-monomers. When the two co-monomers are highly water insoluble, x varies typically between 0.6 and 1. With two relatively water soluble co-monomers, x is close to 0. When two co-monomers with contrasting water solubility are involved, the power dependence is more difficult to predict and ranges from 0 to 1, but high x value are generally found when one of the two monomers is highly hydrophobic. This overall trend can be reconciled with the behavior of a conventional emulsion radical chain polymerization. Graphical abstract

Water-Borne Isocyanate-Free Polyurethane Hydrogels with Adaptable Functionality and Behavior.

Polyurethane hydrogels are attractive materials finding multiple applications in various sectors of prime importance; however, they are still prepared by the toxic isocyanate chemistry. Herein the facile and direct preparation in water at room temperature of a large palette of anionic, cationic, or neutral polyurethane hydrogels by a non-isocyanate route from readily available diamines and new hydrosoluble polymers bearing cyclic carbonates is reported. The latter are synthesized by free radical polymerization of glycerin carbonated methacrylate with water-soluble comonomers. The hydrogel formation is studied at different pH and its influence on the gel time and storage modulus is investigated. Reinforced hydrogels are also constructed by adding CaCl2 to the formulation that in-situ generates CaCO3 particles. Thermoresponsive hydrogels are also prepared from new thermoresponsive cyclic carbonate bearing polymers. This work demonstrates that a multitude of non-isocyanate polyurethane hydrogels are easily accessible under mild conditions without any catalyst, opening new perspectives in the field.

Synergetic Effect of Water-Soluble PEG-Based Macromonomers and Cellulose Nanocrystals for the Stabilization of PMMA Latexes by Surfactant-Free Emulsion Polymerization.

The combination of cellulose nanocrystals (CNCs) and poly(ethylene glycol) methyl ether methacrylate (PEGMA) was evaluated to synthesize stable latexes by surfactant-free emulsion polymerization of methyl methacrylate (MMA). Cellulose-particle interaction was provided due to the dual role of PEGMA, acting as water-soluble comonomer with MMA under emulsion polymerization conditions and able to interact with CNCs, recovered from sulfuric acid hydrolysis (H2SO4-CNCs). After preliminary experiments designed to validate the affinity between CNCs and PEG-stabilized PMMA particles obtained by MMA/PEGMA emulsion copolymerization, the effect of the PEGMA content and molar mass and also of the content of CNCs on the kinetics of the polymerization and the stability of the latexes were investigated. The use of PEGMA300 (Mn = 300 g mol-1, 2-10 wt %) allowed the formation of a stable latex, however, with a broad particle size distribution and the presence of both small (ca. 25-50 nm) and large (ca. 425-650 nm) particles (at 10 wt %, Dn = 278 nm and Dw/Dn = 1.34). Increasing the molar mass of PEGMA (PEGMA950 or PEGMA2080) significantly increased the fraction of small particles. This was explained by the nucleation and growth of small polymer particles adsorbed at the CNCs' surface, resulting in a particular organization where the CNCs were covered by several polymer particles. The influence of the initial amount of CNCs in these systems was finally evidenced, the polymerization being faster as the content of CNCs increased, but only the latexes prepared with 2 and 5 wt % of CNCs were stable.

Polymeric Photoacids Based on Naphthols-Design Criteria, Photostability, and Light-Mediated Release.

The implementation of photoswitches within polymers offers an exciting toolbox in the design of light‐responsive materials as irradiation can be controlled both spatially and temporally. Herein, we introduce a range of water‐soluble copolymers featuring naphthol‐based chromophores as photoacids in the side chain. With that, the resulting materials experience a drastic increase in acidity upon stimulation with UV light and we systematically studied how structure and distance of the photoacid from the copolymer backbone determines polymerizability, photo‐response, and photostability. Briefly, we used RAFT (reversible addition–fragmentation chain transfer) polymerization to prepare copolymers consisting of nona(ethylene glycol) methyl ether methacrylate (MEO9MA) as water‐soluble comonomer in combination with six different 1‐naphthol‐based (“N”) monomers. Thereby, we distinguish between methacrylates (NMA, NOeMA), methacrylamides (NMAm, NOeMAm), vinyl naphthol (VN), and post‐polymerization modification based on [(1‐hydroxynaphthalen‐2‐amido)ethyl]amine (NOeMAm, NAmeMAm). These P(MEO9MAx‐co‐“N”y) copolymers typically feature a 4:1 MEO9MA to “N” ratio and molar masses in the range of 10 kg mol−1. After synthesis and characterization by using NMR spectroscopy and size exclusion chromatography (SEC), we investigated how potential photo‐cleavage or photo‐degradation during irradiation depends on the type and distance of the linker to the copolymeric backbone and whether reversible excited state proton transfer (ESPT) occurs under these conditions. In our opinion, such materials will be strong assets as light‐mediated proton sources in nanostructured environments, for example, for the site‐specific creation of proton gradients. We therefore exemplarily incorporated NMA into an amphiphilic block copolymer and could demonstrate the light‐mediated release of Nile red from micelles formed in water as selective solvent.

Novel copolymers showing interactions of amidinium-carboxylate groups in water

Four hydrophobic amidine containing monomers N-(pyridin-2-yl)methacrylamide (3), 5-(pyridin-2-ylamino)pentyl methacrylate (7), S-5-(isopropenylcarbonyloxy)pentyl-N,N-diphenylthiourea (9) and methyl-5-guanidino-2-methacrylamidopentanoate (12) were synthesized and copolymerized with a water soluble co-monomer N,N-dimethylacrylamide (13) or N-isopropylacrylamide (22). The second component was a copolymer containing methacrylic acid (19) and 13/22. By combination of these two components the formation of amidinium-carboxylate interactions was determined by dynamic light scattering (DLS), 1H-NMR spectroscopy and rheology measurements.

Effect of polymerization conditions on morphology and chromatographic characteristics of polyacrylamide‐based beds (monoliths) for capillary electrochromatography and capillary liquid chromatography

Pioneering research work on continuous or monolithic beds for LC was published in 1989. However, till date there is a lack of complex investigation of various factors affecting the morphology of the beds polymerized from water-soluble co-monomers. In this article the effect of buffer, used as polymerization medium, concentration and pH, and total monomer concentration on the morphology of the resultant continuous beds are discussed. Evaluation of the continuous beds was performed by means of capillary LC, CEC, and inverse size-exclusion chromatography.

Formation of Physical Hydrogels via Host−Guest Interactions of β-Cyclodextrin Polymers and Copolymers Bearing Adamantyl Groups

In this paper, we would like to present a novel system of host−guest hydrogels. By polymerizing adamantyl containing acrylamide monomers (12−15) with water soluble comonomers, we synthesized various copolymers bearing guest components. As host system we applied easily accessible β-cyclodextrin polymers with Mn values of about 30K−100K g mol−1. The viscosity of the resulting hydrogel could be influenced by the concentration of both substances, by the length of the carbon spacer chain of the guest monomer, by the pH value or by the conformation of the β-cyclodextrin polymers. Moreover, the hydrogels stayed stable in solutions of starch hydrolyzing enzyme taka-diastase from Aspergillus oryzae.

A Fluorescent Polymeric Heparin Sensor

Linear copolymers have been developed which carry binding sites tailored for sulfated sugars. All binding monomers are based on the methacrylamide skeleton and ensure statistical radical copolymerization. They are decorated with o-aminomethylphenylboronates for covalent ester formation and/or alkylammonium ions for noncovalent Coulomb attraction. Alcohol sidechains maintain a high water solubility; a dansyl monomer was constructed as a fluorescence label. Statistical copolymerization of comonomer mixtures with optimized ratios was started by AIBN (AIBN=2,2'-azoisobutyronitrile) and furnished water-soluble comonomers with an exceptionally high affinity for glucosaminoglucans. Heparin can be quantitatively detected with an unprecedented 30 nM sensitivity, and a neutral polymer without any ammonium cation is still able to bind the target with almost micromolar affinity. From this unexpected result, we propose a new binding scheme between the boronate and a sulfated ethylene glycol or aminoethanol unit. Although the mechanism of heparin binding involves covalent boronate ester formation, it can be completely reversed by protamine addition, similar to heparin's complex formation with antithrombin III.

Synthesis of Polyvinylacetate‐Sodium Montmorillonite Hybrids by Emulsion Polymerization in the Presence of Anionic Surfactants

The emulsion polymerisation of vinyl acetate (VAc) in presence of sodium dodecylsulphate (SDS) and sodium montmorillonite (NaMMT) is used in order to achieve polymer‐clay hybrids. The influence of the polyvinylacetate (PVAc), SDS, and PVAc‐SDS complex on the NaMMT structure also was investigated. The VAc emulsion polymerization rate exhibits a maximum as the NaMMT concentration increases. The XRD patterns correspond to hybrids with intercalated structure. If a water soluble comonomer, ammonium sulphato ethylmethacrylate (ASEMA) is used for copolymerization with VAc, a exfoliated hybrid structure (from XRD spectra) is obtained. The solid materials were analysed by TGA, FTIR, XRD, SEM, and TEM.

Synthesis of poly(2-hydroxypropyl methacrylate) latex particles via aqueous dispersion polymerization.

Poly(2-hydroxypropyl methacrylate) latexes were prepared by aqueous dispersion polymerization at 60 °C using poly(-vinylpyrrolidone) [PNVP] as a steric stabilizer. The mean latex diameter can be controlled over a wide range by varying the synthesis parameters (initiator type, stabilizer concentration, addition of co-surfactant or comonomer), and narrow size distributions were observed in most cases. These sterically-stabilized latex particles were characterized by electron microscopy, dynamic light scattering, Malvern Mastersizer and FT-IR spectroscopy. The presence of the PNVP stabilizer at the surface of the latex particles was confirmed by X-ray photoelectron spectroscopy and the stabilizer content was assessed by H NMR spectroscopy and nitrogen microanalyses. Colloidally stable surfactant-stabilized poly(2-hydroxypropyl methacrylate) latexes could also be prepared in the absence of any PNVP stabilizer. Since 2-hydroxypropyl methacrylate contains a small amount of dimethacrylate impurity, these latexes are actually lightly cross-linked; their degree of swelling in DO, d-methanol and d-pyridine was investigated using dynamic light scattering and H NMR spectroscopy. Finally, three ionic water-soluble comonomers were successfully copolymerized with 2-hydroxypropyl methacrylate under aqueous dispersion conditions, as judged by aqueous electrophoresis studies.

Novel water soluble copolymers based on thioxanthone: photochemistry and photoinitiation activity

The absorption, luminescence and photoreduction properties of five novel water soluble thioxanthone copolymers are reported. The new polymers have been prepared by copolymerization of 1-methyl-4-(3-acryloxypropoxy) thioxanthone (TX3), 1-chloro-4-acryloxy thioxanthone (TX4), 1-chloro-4-oxyethylacrylate thioxanthone (TX5), and 1-chloro-4-allyloxy thioxanthone (TX6), with two water soluble comonomers, acrylamide (AAm) and 2-acryloxyethyl trimethylammonium iodide (MI). The photoinitiation effectiveness of these new copolymers was studied by photocalorimetry and photodilatometry for acrylamide photopolymerization in aqueous solution and in the presence of a tertiary amine. The results compared to those of the corresponding low molecular weight model compounds, (TX1), 1-methyl-4-(2-hydroxy-3- N, N, N-trimethylammoniumpropoxy) thioxanthone chloride salt, and TX2, 1-chloro-4-(2-hydroxy-3- N, N, N-trimethylammoniumpropoxy) thioxanthone chloride salt. The new copolymers show high polymerisation rates under the experimental conditions used, and confirm that these compounds operate as effective photoinitiators of polymerization. The data are discussed in relation to their photophysical and photochemical properties.

Synthesis, photochemical and photoinitiation activity of water-soluble copolymers with anthraquinone chromophores as side-chain groups

Novel water-soluble anthraquinone copolymers are synthesised by copolymerisation of 2-acryloxy and 2-acrylamido anthraquinone monomers at 1–2% w/w concentration with three water-soluble co-monomers: acrylamide, 2-acrylamido-2-methylpropane sulphonic acid and 2-acryloxyethyl trimethylammonium iodide. The proton and the iodide were replaced on the corresponding obtained copolymers by sodium and chloride using ionic exchange resins. The absorption, phosphorescence (in methanol), photoreduction and microsecond flash photolysis characteristics of the new copolymers are examined in aqueous solution and the results compared with those of a water-soluble low molecular weight anthraquinone, 2-( N, N, N-trimethylammoniumpropoxy) anthraquinone chloride, also synthesised in this work. The photoinduced polymerisation activities of the new products are evaluated by photodilatometry in the presence of triethanolamine as a hydrogen donor. The acrylate anthraquinone copolymers exhibit similar rates and quantum yields of polymerisation to those of the model, while lower values for the acrylamide anthraquinone copolymers are found. The polymerisation activity correlates well with their measured photoreduction quantum yields in water using triethanolamine as the cosynergist.

2-Hydroxypropylmethacrylate based mono- and bifunctional gel beads prepared by suspension polymerization

Spherical and swellable gel beads in the size range 35–200 µm were prepared by suspension polymerization of 2-hydroxypropylmethacrylate (HPMA). In the proposed method, a mixture of cyclohexanol and octanol was used as a diluent phase dispersed in an aqueous medium including poly(vinyl pyrrolidone) (PVP) as the stabilizer. The polymerization was initiated within the organic phase including the monomer and the crosslinker (ethylene glycol dimethacrylate) by an oil soluble initiator benzoyl peroxide. Spherical and swellable gel beads carrying both hydroxyl and carboxyl functional groups were also prepared by suspension copolymerization of HPMA and a water soluble comonomer (methacrylic acid). For this purpose, the suspension polymerization method proposed for HPMA was modified by using poly(vinyl alcohol) as a stabilizer instead of PVP. The effect of initiator concentration, polymerization temperature, monomer/diluent ratio, crosslinker concentration, stirring rate on yield, average size, size distribution, and carboxyl content of the HPMA based gel beads, were investigated. The swelling characteristics of the gel beads were defined. © 2000 Society of Chemical Industry

Study of the mechanism of the emulsifier-free emulsion polymerization of the styrene/4-vinylpyridine system

For the emulsifier-free emulsion copolymerization of styrene with the water-soluble comonomer 4-vinylpyrindine (4VP), and using ammonium persulfate as an initiator, the kinetics, the content of 4VP, the molecular weight and the molecular weight distributions of the polymer at various conversions, and particle morphologies have been investigated. Based on the results obtained, the particle nucleation mechanism was discussed.

Miniemulsion Copolymerization in Batch and Continuous Reactors

Conventional emulsion polymerization (also called macroemulsion polymerization) has been widely used in a variety of industries whereas nucleation and polymerization directly in submicron monomer droplets (i.e., miniemulsion polymerization) has been primarily an academic curiosity. However, much interest has recently been generated on the basis of the prospects of incorporating very hydrophobic ingredients into a water-based system via miniemulsion polymerization. In this work, a very hydrophobic acrylic monomer, 2-ethylhexyl acrylate, is copolymerized with methyl methacrylate using a miniemulsion recipe. The goal of this paper is to examine emulsion copolymerization kinetics for monomers of very different water solubilities. It is believed that the effects of water solubility differences between comonomers are minimized using a miniemulsion recipe. In this case, the copolymer composition is more uniform in batch miniemulsion copolymerization experiments, relative to batch macroemulsion copolymerizations. The same behavior is, however, not observed in a continuous-stirred tank reactor. At even moderate steady-state conversions, there is a substantial driving force for monomer transport that favors incorporation of the more water-soluble comonomer.

Synthesis, photochemical and photoinitiation activity of water soluble copolymers with pendent benzil chromophores

In the present paper the synthesis of three novel water soluble copolymers with benzil pendant groups are described. The new polymers have been prepared by copolymerization of the obtained benzil acrylate, 1-phenyl-2-[4-(2-methacroyloxyethoxy)phenyl]ethandione-1,2 (MBz) with three water soluble comonomers: acrylamide, 2-acrylamido-2-methylpropane sulphonic acid and 2-acryloxyethyl trimethylamonio iodine. The absorption, luminescence, photoreduction and microsecond flash photolysis characteristics of the new copolymers were examined in water and methanol and the results compared to the corresponding low molecular weight compound. The photoinduced polymerization activities of the new products have been determined by photodilatometry in the presence of a tertiary amine. The copolymers exhibit polymerization rates and quantum yields similar to those of the low molecular weight model compounds.

Copolymerization of acrylamide with various water-soluble monomers

The radical copolymerization of acrylamide with water-soluble monomers of various natures up to high conversion degrees have been studied in water or DMSO. Dimethylaminoethyl methacrylate sulfate, sodium vinylsulfonate, acrylamido-2-methyl-propanesulfonic acid and N-vinylpyrrolidone were used as the water-soluble comonomers. The composition of the copolymers synthesized in the aqueous solutions remains practically unchanged in all systems studied until monomers conversion degrees as high as 50–70% are reached. One possible reason for the observed behaviour is hydrophobic interactions in the aqueous solution of polymers.

Emulsion polymerization with water soluble comonomers in batch and continuous reactors

AbstractEmulsion copolymerization reactions which include monomers that have significant solubility in the water phase are described and modeled. The reactions that take place in the aqueous phase are considered as is the influence of water‐soluble comonomers on radical transport out of the monomer‐swollen polymer particles. Experimental characterization of the oligomers formed in the aqueous phase is also a subject of this paper.

Kinetic features of the emulsion homo- and copolymerization of certain water soluble polymers

The kinetics and mechanism of the emulsion homo- and copolymerization of methacrylate with the amides of acrylic and methacrylic acids are studied. The observed differences in the copolymerization constants for the emulsion process compared with reaction in solution are due to the changes in the concentrations of the comonomers in the reaction zone. Acrylamide has an insignificant effect on the rate of emulsion polymerization, and methacrylamide decreases it because of slowing down of the reaction in the aqueous phase. The nucleation of monomer-polymer particles is achieved by different mechanisms, the ratio between which depends on the presence of water-soluble comonomers and the initiation rate. Over a specific range of ammonium persulphate concentrations several radicals can coexist in the latex particles, and a gel effect arises. These features of the reaction lead to a situation where the kinetic orders with respect to the emulsifier and initiator depend on the polymerization conditions.

Kinetics and mechanism of emulsifier‐free emulsion polymerization. III. Styrene/nonionic comonomer (2‐hydroxyethyl methacrylate) system

AbstractThe emulsifier‐free emulsion polymerizations of styrene in the presence of about 0.33–2.7% (relative to styrene) of the water soluble comonomer, 2‐hydroxyethyl methacrylate (HEMA), and of the initiator, potassium persulfate (KPS), were carried out. It was found that KPS plays a predominant role in the particle nucleation process, since the number density of polymer particles (Np) was dependent on the 0.97‐power of [KPS]. The nucleation ability of HEMA was weak, since Np was dependent only on the 0.17‐power of [HEMA]. The particle nucleation stage ceased quite early before 1% conversion, leading to nearly monodispersed polymer particles. The nucleation is suggested to be via the homogeneous nucleation mechanism. The particles grow via the core‐shell structure mechanism (shell region polymerization), since the particle size is rather large—from 1500 to 6000 Å. The amount of HEMA can affect the shell thickness and physical properties of the shell, such as the monomer swelling capacity and monomer diffusion rate.