Monomer Solubility Research Articles

Metastable Polymerization of Sickle Hemoglobin in Droplets

Sickle cell disease arises from a genetic mutation of one amino acid in each of the two hemoglobin β chains, leading to the polymerization of hemoglobin in the red cell upon deoxygenation, and is characterized by vascular crises and tissue damage due to the obstruction of small vessels by sickled cells. It has been an untested assumption that, in red cells that sickle, the growing polymer mass would consume monomers until the thermodynamically well-described monomer solubility was reached. By photolysing droplets of sickle hemoglobin suspended in oil we find that polymerization does not exhaust the available store of monomers, but stops prematurely, leaving the solutions in a supersaturated, metastable state typically 20% above solubility at 37 °C, though the particular values depend on the details of the experiment. We propose that polymer growth stops because the growing ends reach the droplet edge, whereas new polymer formation is thwarted by long nucleation times, since the concentration of hemoglobin is lowered by depletion of monomers into the polymers that have formed. This finding suggests a new aspect to the pathophysiology of sickle cell disease; namely, that cells deoxygenated in the microcirculation are not merely undeformable, but will actively wedge themselves tightly against the walls of the microvasculature by a ratchet-like mechanism driven by the supersaturated solution.

Self-Controlled Synthesis of Hyperbranched Poly(ether ketone)s from A3 + B2 Approach via Different Solubilities of Monomers in the Reaction Medium

Hyperbranched poly(ether ketone)s (PEK's) were synthesized via A3 + B2 polymerization approach without forming cross-linked products, because the polymer-forming process based on Friedel−Crafts reaction was kinetically controlled by the solubility difference of monomers in the viscous hydrophilic reaction medium, poly(phosphoric acid) (PPA)/phosphorus pentoxide (P2O5). The hydrophilic trimesic acid as an A3 monomer is soluble in the reaction medium, while hydrophobic diphenyl ether and 1,4-diphenoxybenzene as B2 monomers are marginally soluble. It is hypothesized that the gelation was avoided because of the following two factors: (i) self-regulated feeding of the arylether monomers into the system driven by their poor solubility and phase separation from PPA/P2O5 medium; (ii) reaction-medium-induced isolation of growing macromolecules promoted by the high bulk viscosity. Both polymerization experiments based on equimolar or equifunctional stoichiometry (A3:B2) resulted in completely soluble hyperbranched...

Initiation Efficiency Reduction in Semicontinuous Styrene and Butyl Acrylate Emulsion Copolymerization Reactions

AbstractThe decrease of initiation efficiency (radical entry efficiency) during seeded emulsion copolymerizations of styrene and butyl acrylate with different residual monomer reduction strategies was evaluated. Experiments were carried out using 50 and 99wt.% of styrene in monomer feed stream. Simulations were performed with a detailed mathematical model of the process that takes into account the diffusion control of initiation, propagation and termination. Results showed that the radical entry into polymer particles is strongly influenced by the aqueous phase kinetics and by the monomer solubility in aqueous phase. Simulation results were compared to experimental results of residual monomer and showed that the residual monomer content can be reduced by a temperature increase at the end of the polymerization. However, an additional feeding of more initiator, even when combined with such an increase of temperature, did not lead to a smaller residual monomer content due, mainly, the kinetic of termination in aqueous phase and radical anchoring. A model that accounts for the reduction of initiator efficiency (free radical entry efficiency) was successfully used to explain the behavior of the experimental observations and was able to correctly predict the qualitative trends of the effectiveness of different residual monomer reduction strategies.

Kinetics study on melt grafting copolymerization of LLDPE with acid monomers using reactive extrusion method

AbstractGraft copolymerization in the molten state is of fundamental importance as a probe of chemical modification and reactive compatibilization. However, few grafting kinetics studies on reactive extrusion were carried out for the difficulties as expected. In this work, the macromolecular peroxide‐induced grafting of acrylic acid and methyl methacrylate onto linear low density polyethylene by reactive extrusion was chosen as the model system for the kinetics study; the samples were taken out from the barrel at five ports along screw axis and analyzed by FTIR, 1H NMR, and ESR. For the first time, the time‐evolution of reaction rate, the reaction order, and the activation energy of graft copolymerization and homopolymerization in the twin screw extruder were directly obtained. On the basis of these results, the general reaction mechanism was tentatively proposed. It was demonstrated that an amount of chain propagation free radicals could keep alive for several minutes even the peroxides completely decomposed and the addition of monomer to polymeric radicals was the rate‐controlled step for the graft copolymerization. The results presented here revealed that the relative importance of graft copolymerization compared with homopolymerization mainly depended on the monomer solubility and reactivity, while the process parameters such as reaction temperature also influenced the reaction tendency. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4301–4312, 2006

Kinetic Studies upon the Influence of Cyclodextrin on the Polymerization of Methacrylamides in Homogenous Aqueous Solution

AbstractSummary: N‐methacryloyl‐1‐aminopropane (1), N‐methacryloyl‐1‐aminobutane (2), N‐methacryloyl‐1‐aminopentane (3), and N‐methacryloyl‐1‐aminohexane (4) are synthesized and treated with an aqueous solution of randomly methylated β‐cyclodextrin (Me‐β‐CD) to form the water‐soluble host‐guest complexes 1a–4a. In case of the aqueous polymerization of the free monomers 1–4 the initial polymerization rate increases with increasing water solubility. The opposite effect is observed in the case of the polymerizations of the Me‐β‐CD‐complexed methacrylamide monomers 1a–4a. The polymerization rates are increased with increasing alkyl chain length of the complexed monomers 1a–4a and decreasing water solubility of the free monomers 1–4.Initial polymerization rate v0 of CD‐complexed monomers 1a–4a (○) vs. water solubilities of monomers 1–4 (▪).magnified imageInitial polymerization rate v0 of CD‐complexed monomers 1a–4a (○) vs. water solubilities of monomers 1–4 (▪).

Nanoparticle formation by highly diffusion-controlled emulsion polymerisation

Emulsion polymerisations of several monomers with different water solubilities including styrene, butyl acrylate, methyl methacrylate, vinyl acetate, and methyl acrylate were carried out under highly diffusion-controlled conditions. The monomer was placed on top of an aqueous solution of an emulsifier and an initiator, while being gently stirred. Polymerisation occurred by diffusion of monomer from the monomer phase via the interface to the micellar solution. Nanoparticles as small as 25 nm were produced as a result of reduced particle growth and delayed depletion of emulsifier micelles. Nanolatexes with relatively high solids content (20%) but with a low surfactant/monomer ratio (1/50) were obtained. The monomers with the highest solubility, with the exception of methyl acrylate, produced the smallest particles. The rate of diffusion-controlled polymerisation was found to be almost proportional to the saturation monomer concentration in the water phase ( R p ∝ [ M ] w , sat 0.97 ) . The results were compared with those obtained with a high rate of agitation which allowed kinetics of polymerisation to become the rate determinant. While particles obtained by kinetics-controlled emulsion polymerisation of the monomers were large, as well as similar in size, particles obtained from diffusion-controlled runs were small, but different in size. On the other hand, particles made by kinetics-controlled emulsion polymerisation had increasing surface coverage (by emulsifier) with monomer solubility in water. Whereas, nanoparticles made by diffusion-controlled emulsion polymerisation reached almost a constant surfactant coverage independent of the monomer type (except for methyl acrylate), a surface coverage as low as 0.20 was found to be sufficient for stabilisation of nanoparticles.

Electrosyntheses of high quality poly (5-cyanoindole) films in boron trifluoride diethyl etherate containing additional diethyl ether

High quality poly (5-cyanoindole) (P5CI) films were synthesized electrochemically by direct anodic oxidation of 5-cyanoindole on a stainless steel sheet in boron trifluoride diethyl etherate (BFEE) + 50% diethyl ether (EE) (v/v) + 0.05 mol L −1 Bu 4NBF 4. They can be peeled off the electrode into freestanding films. The introduction of EE to BFEE can improve the solubility of monomer. The oxidation potential of 5-cyanoindole in this medium was measured to be only 1.15 V versus SCE, which was lower than that determined in acetonitrile + 0.1 mol L −1 Bu 4NBF 4 (1.58 V versus SCE). BFEE + 50% EE + 0.05 mol L −1 Bu 4NBF 4 was tested to be a better medium than acetonitrile for the electrosyntheses of P5CI films. P5CI films obtained from BFEE + 50% EE + 0.05 mol L −1 Bu 4NBF 4 showed good electrochemical behavior, good thermal stability with conductivity of 10 −2 S cm −1. The polymerization of 5-cyanoindole ring through 2,3-position was proved by FT-IR and 1H NMR spectroscopy. As-formed P5CI films were thoroughly soluble in strong polar organic solvent dimethyl sulfoxide (DMSO) while partly soluble in tetrahydrofuran (THF) or acetone. Fluorescence spectral studies indicated that P5CI was a good blue-light emitter.

Determination of the solubility of a monomer in water by multiple headspace extraction gas chromatography

AbstractIn water‐based polymerization (suspension, microsuspension, emulsion, miniemulsion, and microemulsion polymerization), the solubility of the monomer in the aqueous phase can have profound effects on the final polymer product. This article demonstrates a novel method for the determination of monomer solubility in water with headspace gas chromatography (GC). In this method, an excess amount of an organic solute of interest was added into a closed headspace vial containing a given volume of water. The organic solute and water in the vial was well mixed by strong hand shaking; then, the equilibrated vapor solute in the vial at a desired temperature was measured by headspace GC with a multiple headspace extraction mode. In each headspace extraction, a part of the vapor phase in the vial was vented for GC analysis and replaced with an inert gas. The excess amount of solute in aqueous solution was eventually removed from the vial after multiple headspace extractions, and the solute concentration in water reached its saturation point. After that point, the concentration of the solute in the vapor dramatically decreased in each subsequent headspace extraction. By plotting vapor concentration versus headspace extraction number, we determined the transition point. The vapor concentration at this point corresponded to the solute solubility, which was calculated through a calibration. This method was very simple and automated; it could easily be used for organic solute solubility measurement at an elevated temperature. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1296–1301, 2006

Plasma graft polymerization of glycidyl methacrylate and cyclodextrin immobilization

Glycidyl methacrylate (GMA) was graft-polymerized to plasma treated fibers after short exposure to air, and β-cyclodextrin was chemically bound to the grafted surface. Graft polymerization is achieved by glycidyl methacrylate at the lower concentration of 2 w/v% in the aqueous solution with sodium dodecylsulfate that was added to increase the monomer solubility. The β-cyclodextrin immobilized fibers adsorbed phenols effectively in the aqueous solution.

Lipid transfer between cationic vesicles and lipid–DNA lipoplexes: Effect of serum

Differential scanning calorimetry was used to examine the lipid exchange between model lipid systems, including vesicles of the cationic lipoids ethyldimyristoylphosphatidylcholine (EDMPC), ethyldipalmitoylphosphatidylcholine (EDPPC) or their complexes with DNA (lipoplexes), and the zwitterionic lipids (DMPC, DPPC). The changes of the lipid phase transition parameters (temperature, enthalpy, and cooperativity) upon consecutive temperature scans was used as an indication of lipid mixing between aggregates. A selective lipid transfer of the shorter-chain cationic lipoid EDMPC into the longer-chain aggregates was inferred. In contrast, transfer was hindered when EDMPC (but not EDPPC) was bound to DNA in the lipoplexes. These data support a simple molecular lipid exchange mechanism, but not lipid bilayer fusion. Exchange via lipid monomers is considerably more facile for the cationic ethylphosphatidylcholines than for zwitterionic phosphatidylcholines, presumably due to the higher monomer solubility of the charged lipids. With the cationic liposomes, lipid transfer was strongly promoted by the presence of serum in the dispersing medium. Serum proteins are presumed to be responsible for the accelerated transfer, since the effect was strongly reduced upon heating the serum to 80 °C. The effect of serum indicates that even though much lipoplex lipid is inaccessible due to the multilayered structure, the barrier due to buried lipid can be easily overcome. Serum did not noticeably promote the lipid exchange of zwitterionic liposomes. The phenomenon is of potential importance for the application of cationic liposomes to nonviral gene delivery, which often involves the presence of serum in vitro, and necessarily involves serum contact in vivo.

Simplified multiple headspace extraction gas chromatographic technique for determination of monomer solubility in water

This paper reports an improved headspace gas chromatographic (GC) technique for determination of monomer solubilities in water. The method is based on a multiple headspace extraction GC technique developed previously [X.S. Chai, Q.X. Hou, F.J. Schork, J. Appl. Polym. Sci., in press], but with the major modification in the method calibration technique. As a result, only a few iterations of headspace extraction and GC measurement are required, which avoids the “exhaustive” headspace extraction, and thus the experimental time for each analysis. For highly insoluble monomers, effort must be made to minimize adsorption in the headspace sampling channel, transportation conduit and capillary column by using higher operating temperature and a short capillary column in the headspace sampler and GC system. For highly water soluble monomers, a new calibration method is proposed. The combinations of these technique modifications results in a method that is simple, rapid and automated. While the current focus of the authors is on the determination of monomer solubility in aqueous solutions, the method should be applicable to determination of solubility of any organic in water.

Molecular Description of Erosion Phenomena in Biodegradable Polymers

A new model for the erosion kinetics of semicrystalline surface-erodible homopolymers and copolymers is presented. The model is derived for a class of surface-erodible polyanhydride copolymers, with the goal of describing erosion in terms of fundamental, elementary processes. This model is based on an accurate description of copolymer microstructure and can thereby account for the heterogeneous erosion due to microphase separation and crystallinity. In addition to accurately predicting the overall erosion profile and the release of individual monomer species, several key phenomena that occur during erosion are described. These include precipitation of slightly soluble degradation products inside the pores of the erosion zone and pH changes during erosion due to dissolution of acidic monomers and the consequent changes in monomer solubility. This model also motivates future experiments to investigate predicted phenomena such as the effects due to local changes in pH and degradation rate constants for cryst...

Measurement of the Solubilities of Vinylic Monomers in Water

In aqueous emulsion and miniemulsion polymerization, the product may be dependent upon the ability of the monomer(s) to diffuse across the continuous aqueous phase. This, in turn, is dependent upon the solubility of the monomer in the aqueous phase. Reference solubilities are often difficult to find or measure using different methods and temperatures. This paper presents the solubilities of a number of low-solubility monomers at 60 °C, using the multiple headspace extraction gas chromatography technique described by Chai et al. (J. Appl. Polym. Sci. 2004, in press). The data were collected under uniform conditions and provide a base for judging relative solubilities. These data will be useful not only as absolute measurements of water solubility but also as a tool to judge the relative solubilities of various monomers.

Co-effect of aqueous solubility of drugs and glycolide monomer on in vitro release rates from poly(D,L-lactide- co-glycolide) discs and polymer degradation

The objective of this study was to investigate the effect of aqueous solubility of model drugs and glycolide monomer (GM) from poly(D,L -lactide-co-glycolide) (PLGA) discs on in vitro release rates and polymer degradation. 5-Fluorouracil (5-FU), a water-soluble compound, and dexamethasone in a water-insoluble base form were selected as model drugs. Glycolide monomer, that has moderate solubility in water, was a non-toxic and biodegradable additive as a derivative material of hydrolysis of PLGA in order to obtain desirable drugs release rates. PLGA discs with or without GM were formulated by means of compression molding method. The prepared polymeric discs were incubated at 37°C in phosphate-buffered saline (PBS, pH 7.4) and characterized at scheduled time points for water uptake, mass loss, diameter and morphology change, molecular weight and composition change using scanning electron microscopy (SEM), gel-permeation chromatography (GPC), and 1H-NMR, respectively. The supernatants were taken out of the sample vials and were analyzed for drug release. The 5-FU release was found to be increasing in proportion to the drug loading amount with an initial burst for 5 days, while dexamethasone release showed inverse relationship with the increasing drug loading amount. However, the release behaviors of 5-FU and dexamethasone polymeric discs containing GM showed faster release rates than control discs (without GM) and did not show lag periods during the in vitro release test due to adding GM, which acted as a channeling agent that has moderate solubility in water. Polymer degradation was found to be affected by aqueous solubility of drugs and GM. In conclusion, we observed that drugs release rates were influenced by their aqueous solubility and loading amount and also GM plays a major role in controlling drug release rates regardless of solubility of drugs. This system appears to be promising for controlled drug delivery aimed at local therapy.

Self‐Assembly and Self‐Organization: Important Processes, But Can We Predict Them?

Two aggregation processes of amphiphilic molecules, i.e., molecules consisting of a hydrophilic head group and a hydrophobic tail, are presented. Self‐assembly of these amphiphiles is based on non‐directed and non‐selective intermolecular interactions such as van der Waals attraction between hydrocarbon chains and repulsion between charged or hydrated head groups. Self‐organization, on the other hand, is based on directed and selective interactions such as hydrogen bonds. The aggregation behavior of amphiphiles and surfactants is often explained using the molecule‐specific packing parameter P = v/a 0 l c, with a 0 being the optimal head group area, v the volume of the hydrocarbon chain, and l c the critical chain length. The reliability of the packing parameter concept in predicting mesophases and molecular aggregates based on these geometrical considerations is evaluated, and shortcomings of this concept are illustrated with many examples. More reliable model simulations are presented, which provide reasonable to good agreement between calculated phase behavior and experimental results. A hands‐on approach in predicting and tailoring self‐assembly and self‐organization is proposed using the monomer solubility as a measure, and its feasibility is demonstrated.

Influence of tacticity on solubility of propene monomer in isotactic and syndiotactic polypropylene

Solubility of propene monomer in isotactic polypropylene (i-PP) and syndiotactic polypropylene (s-PP) is investigated using Gibbs ensemble MC simulation. Tacticity was found to influence the solubility with propene having higher solubility in i-PP. The higher solubility is explained by the more favorable interaction of the propene molecules with i-PP. By analyzing the pair correlation functions of propene with PP it was found that propene favors being in the neighborhood of the PP side methyl groups. In addition, it was found that the propene two end segments orient themselves so that they can be in the proximity of the side methyls. This study provides insight into the effect of tacticity and molecular architecture on solubility in polymers.

Influence of cyclodextrin and its glucose units on polymerization of styrene

AbstractThe free radical polymerization of styrene in water in the presence of β‐cyclodextrin (β‐CD) without using surfactants is described. The effect of β‐CD which greatly accelerated the polymerization, was wholly contributed to the formation of host–guest complexes with hydrophobic monomer to increase the monomer solubility in water. Through adding toluene that is similar in structure to monomer styrene to block the formation of β‐CD with styrene monomer, we found that just like free glucose, the glucose units of β‐CD could also accelerate the polymerization. The polymer particles with narrow particle‐size distribution and clear surface were prepared without using any surfactants and solvent mixtures. Copyright © 2004 Society of Chemical Industry

Preparation of drug delivery biodegradable PLGA nanocomposites and foams by supercritical CO2 expanded ring opening polymerization and by rapid expansion from CHCIF2 supercritical solutions

ABSTRACTThe synthesis of poly(lactic-co-glycolic acid) (PLGA) by the ring opening copolymerization of D, L-lactide and glycolide was performed at 110 °C to 130 °C using Sn(Oct)2 as catalyst, 1, 10-decanediol as initiator in a supercritical sc-CO2 expanded medium at pressures of up to 3, 500 psi. Due to the limited monomer solubility in sc-CO2 at low temperatures (70 °C), only Mn = 2, 500 is typically obtained. However, molecular weight increases with both temperature and sc-CO2 pressure. Thus, Mn = 13, 000 (PDI = 1.28) was obtained at 110 °C - 130 °C even in the absence of fluorinated surfactants. Biodegradable drug delivery nanocomposites based on dexamethasone and poly(lactic acid) (PLA) and poly(lactide-co-glycolide) (PLGA) were prepared by the rapid expansion of the corresponding supercritical CHClF2 solutions (110 °C, 200-300 bar) in air (RESS) and in toluene (RESOLV). The RESS process leads to a broad particle size distribution (100-500 nm) while the RESOLV generates a narrower distribution centered around 100 nm and is accompanied by the formation of a few large particles, most likely due to aggregation.

Toward an understanding of the role of water‐soluble oligomers in the emulsion polymerization of styrene–butadiene–acrylic acid. Function of carboxylic acid

AbstractIn a further effort to understand the role of water‐soluble oligomers formed during the emulsion terpolymerization of styrene/butadiene/acrylic acid (St/Bu/AA), the reaction temperature, initiator concentration, and ionic strength were varied and the kinetics and resulting oligomers were characterized as a function of reaction time. The rate of polymerization (Rp) was observed to increase with increasing temperature and initiator concentration; the reasons for this vary. The increase in Rp with increasing initiator concentration is mainly attributed to the increase in the number of oligomeric radicals formed and, subsequently, the resulting number of particles (Np). Increasing the temperature increases the water solubility of both monomers and polymers, which results in changes in the composition and molecular weight of the oligomeric radicals being formed. The primary reaction locus in the St/Bu/AA system was noted to shift to the aqueous phase after most of the styrene and butadiene had reacted, based on the unreacted AA profile. The role of water‐soluble oligomers (both oligomeric radicals and dead oligomers) during the emulsion polymerization of St/Bu with acrylic acid can be described by three periods: (1) particle generation and (2) before and (3) after the critical surface saturation concentration (CSSC) is reached during the particle growth period. The incorporation of AA monomer into the oligomer chains after the CSSC may cause destabilization of the latexes through a bridging flocculation mechanism. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1988–1999, 2003

Sugar monomer and oligomer solubility: data and predictions for application to biomass hydrolysis.

Oligomer solubility could potentially play an important role in controlling the rates and yields in the thermochemical hydrolysis of hemicellulose as a pretreatment for subsequent enzymatic conversion of cellulose. However, limited data or models are available to describe the aqueous solubility of sugar monomers and oligomers. In this work, we measured the solubilities of sugars common to many biomass feedstocks in the temperature range of 25-30 degrees C. Then we reviewed solubility models for sugars from the open literature. Finally, we applied models to test their ability to describe this and other data reported in the literature. It was found that the solubility of sugar monomers was not well described by the ideal solubility law or other more complex models. However, with an empirical adjustment to the enthalpy of fusion, the ideal solubility law was able to approximately predict the solubility of cello-oligomers. Based on these results, solubilities for low molecular weight xylo-oligomers are predicted to investigate their possible importance in pretreatment and define further experimental measurements needed to improve our understanding of sugar and oligomer solubility.