N-alkyl Acrylamide Research Articles

Synthesis and emulsion stability of salt resistant viscosity reducer for heavy oil reservoirs with varying salinities

To address the inadequate salt resistance of viscosity reducers and their limited applicability to reservoirs with single salinity, we synthesized salt-resistant viscosity reducers PANxAn in this study. These compounds were derived from fatty alcohol polyoxyethylene ether acrylate, N-alkyl acrylamide, acrylamide, and 2-acrylamido-2-methylpropanesulfonic acid. The structures were identified using nuclear magnetic hydrogen spectroscopy. We investigated the effects of the hydrophilic group ethoxy-chain length (n = 14, 16, 18, 20 and 22) and hydrophobic group alkyl-chain length (x = 12, 14, 16, and 18) on the salt resistance, interfacial activity, wettability, interfacial viscoelasticity and emulsification viscosity reduction performance of the viscosity reducers. Futher, the structures of the viscosity reducers which can adapt to different salinities were determined. Based on the emulsification viscosity reduction effect, PAN14A16, PAN12A16, PAN12A18, PAN12A20/PAN16A16 and PAN12A22/PAN18A16 adapted to salinities range of 2 × 104-6 × 104, 4 × 104-8 × 104, 6 × 104-10 × 104, 8 × 104-12 × 104 and 10 × 104-14 × 104 mg/L, respectively. At the optimal salinity, PANxAn reduced the oil–water interfacial tension from 28.3 to 5.0 mN/m, dynamic contact angle from 130.0° to 61.0°, and heavy oil viscosity from 454.6 to 60.0 mPa·s with a viscosity reduction rate of 86.80 %. The synthesis of salt-resistant PANxAn provides theoretical guidance and application value for enhancing the recovery efficiency of viscosity-reducer flooding in high-salinity heavy oil reservoirs.

Direct synthesis of poly(N-alkyl acrylamide) (co)polymers with pendant reactive amino groups by organocatalyzed amidation of polymethylacrylate

Post-polymerization modification of poorly reactive polyacrylates using efficient catalytic transesterification and amidation reactions has recently emerged as a valuable tool to access diversely functionalized poly(meth)acrylates and poly(meth)acrylamides. The method is particularly useful to introduce functional groups incompatible with the polymerization mechanism, such as non-protected reactive amino groups. In this work, we explored the TBD-catalyzed amidation of polymethylacrylate (PMA) with various difunctional amines to obtain polyacrylamide homo- and copolymers with a pendant reactive amine group. As anticipated, functional polymers could not be attained from amidation with ethylenediamine, because of competing cross-linking side reactions, but could be prepared from the mono-Boc-protected ethylenediamine instead, requiring, however, additional unwanted protection and deprotection steps. More interestingly, we found that the direct amidation of PMA with unprotected N-ethylethylenediamine is an efficient method for preparing secondary amine functionalized polymers, without the occurrence of crosslinking side-reaction even at lower catalyst loading. The crucial role of the ethyl group to prevent side reactions was clearly demonstrated as the use of N-methyl ethylenediamine led to crosslinking. The utility of the developed platform for the rapid preparation of a series of hydrophilic copolymers and hydrogel materials is also demonstrated. The hydrogels were prepared by reacting the secondary amine side chains with methacrylic anhydride, followed by photocuring in the presence and absence of dithiols.

Synthesis of poly(n-alkyl acrylamides) and evaluation of nanophase separation effects by temperature-dependent infrared spectroscopy

Common linear polymers are known to undergo phase changes at the glass-transition temperature (Tg) and the melting point (Tm). In recent years, it has also been shown that molecules with long aliphatic side chains can give rise to a backbone-independent melting phenomenon, known as nanophase separation. This effect describes the self-assembly — independent of the polymer backbone — of alkyl side chains into semi-crystalline nanostructures. This work presents optimized, gram scale synthesis routes for dodecyl and octadecyl acrylamide and their respective homopolymers. Differential scanning calorimetry (DSC) experiments detected a broad endothermal signal for poly(n-dodecyl acrylamide) at − 29 °C and a narrower, more intense signal for poly(n-octadecyl acrylamide) at 34 °C. These signals indicate the nanophase separation TM of the alkyl side chains. We undertook the first temperature-controlled infrared spectroscopy investigations of these materials revealing a clear hypsochromic shift of the C–H stretching signals above TM and the amide I signal shifts that occurred only above and below Tg. These results provide further evidence, that the side chains act independently of the polymer backbone and show that infrared spectroscopy is a powerful tool for monitoring conformational changes in polymer side chains.Graphical abstract

Mechanistic insight into impact of clay on compressive elasticity of poly(N-alkyl acrylamide)/Laponite-based nanocomposite cryo-beads

Relationship between formation pathway and Hertzian elasticity of poly(N-isopropylacrylamide-co‑sodium acrylate)/Laponite® XLG, P(NIPA-NaA)/LAP, based nanocomposite cryo-beads was evaluated. Millimeter-sized nanocomposite cryo-beads were prepared by combination of dropwise freezing into cryogenic liquid (DFLC) method with sedimentation cryogelation method. pH-sensitive 3D-templete was formed by conducting free-radical crosslinking cryopolymerization of NIPA and NaA in the presence of synthetic hectorite Laponite® XLG as inorganic crosslinker and N,N′-methylenebis(acrylamide) as chemical crosslinker. The effects of network template, ionic comonomer, inorganic clay incorporation, pH- and ionic strength of swelling medium on the swelling and elasticity were evaluated as a function of bead size. The deformability of swollen cryo-beads was investigated using Hertzian elasticity. The crosslink density and Hertz modulus of nanocomposite beads vary with the droplet size and the polymer spheres with low crosslink density tend to absorb more water. In DFLC method, the desired sphere size and swelling can be adjusted by selecting the needle size used for dripping. The swelling degree increased significantly as the size of nanocomposite cryo-beads increased. At a fixed swelling ratio, the cylindrical nanocomposite cryogels exhibited greater elastic moduli and crosslink density than that of spherical gels. Correlation of elastic modulus of cryo-beads with swelling and cross-linked polymer concentration predicted a higher scaling exponent than the classical estimate for swelling in good solvents. It was investigated how the presence of 30 mol% pH-sensitive anionic comonomer NaA in the structure of all nanocomposite gels affects their pH-dependent swelling behavior. At pH < 5.7, the gels exhibited a lower swelling ratio, whereas at pH > 6.6 they tended to swell and followed second-order swelling kinetics by Fickian diffusion. When pH of swelling medium was alternately changed, all gels exhibited a pH-switch and swelling rate was two times higher than shrinkage rate. By investigating the effect of KCl, NaCl and K2CO3 on the swelling of cryobeads, it was determined how the salt cation changes the electrostatic repulsion between network charges. Nanocomposite cryo-beads showed fast pH-responsiveness and immediately reabsorbed the water they lost due to pH change, therefore, they can be designed as drug release carriers by pH-switching modulation.

Reactivity of secondaryN-alkyl acrylamides in Morita–Baylis–Hillman reactions

The Morita–Baylis–Hillman (MBH) reaction of secondary N-alkyl acrylamides, discarded up to now from investigations of the scope of activated alkenes, was studied. Optimization of the reaction conditions revealed that a balance must be found between activation of the MBH coupling reaction and that of the undesired competitive aldehyde Cannizzaro reaction. Using 3-Hydroxyquinuclidine (3-HQD) in a 1:1 water-2-MeTHF mixture provides the appropriate conditions that were applicable to a wide range of diversely substituted secondary N-alkyl acrylamides and aromatic aldehydes, giving rise to novel amide-containing MBH adducts under mild and clean conditions. Supplementary Materials: Supplementary material for this article is supplied as a separate file: crchim-117-suppl.pdf La réaction de Morita–Baylis–Hillman (MBH) de N-alkyl acrylamides secondaires, écartés jusqu’alors des travaux sur la variabilité des alcènes activés dans cette réaction, a été étudiée. L’optimisation de la réaction a fait apparaître un équilibre à trouver entre l’activation du couplage par réaction MBH et celle de la transformation de l’aldehyde par réaction de Cannizzaro. L’utilisation de la 3-hydroxyquinuclidine (3-HQD) et d’un mélange eau-2-MeTHF 1:1 comme solvant sont les conditions appropriées, applicables à une variété de N-alkyl acrylamides secondaires diversement substitués et d’aldéhydes aromatiques, menant à une série de nouveaux adduits MBH contenant un motif amide, dans des conditions douces et propres. Compléments : Des compléments sont fournis pour cet article dans le fichier séparé : crchim-117-suppl.pdf

Expansion Microscopy with a Thermally Adjustable Expansion Factor Using Thermoresponsive Biospecimen–Hydrogel Hybrids

Expansion microscopy (ExM) is a technique in which swellable hydrogel-embedded biological samples are physically expanded to effectively increase imaging resolution. Here, we develop thermoresponsive reversible ExM (T-RevExM), in which the expansion factor can be thermally adjusted in a reversible manner. In this method, samples are embedded in thermoresponsive hydrogels and partially digested to allow for reversible swelling of the sample-gel hybrid in a temperature-dependent manner. We first synthesized hydrogels exhibiting lower critical solution temperature (LCST)- and upper critical solution temperature (UCST)-phase transition properties with N-alkyl acrylamide or sulfobetaine monomers, respectively. We then formed covalent hybrids between the LCST or UCST hydrogel and biomolecules across the cultured cells and tissues. The resulting hybrid could be reversibly swelled or deswelled in a temperature-dependent manner, with LCST- and UCST-based hybrids negatively and positively responding to the increase in temperature (termed thermonegative RevExM and thermopositive RevExM, respectively). We further showed reliable imaging of both unexpanded and expanded cells and tissues and demonstrated minimal distortions from the original sample using conventional confocal microscopy. Thus, T-RevExM enables easy adjustment of the size of biological samples and therefore the effective magnification and resolution of the sample, simply by changing the sample temperature.

Hydrophilic Submicron Nanogel Particles for Specific Recombinant Proteins Extraction and Purification.

In biomedical diagnosis and bionanotechnologies, the extraction and purification of proteins and protein derivatives are of great interest. In fact, to purify recombinant proteins for instance, new methodologies and well appropriate material supports need to be established and also to be evaluated. In this work, hydrophilic nanohydrogel particles were prepared for recombinant proteins extraction for purification purpose. The prepared nanohydrogel polymer-based particles are hydrophilic below the volume phase transition temperature (TVPT) and dehydrated above the TVPT, due to the thermally sensitive poly(N-alkyl acrylamide) and poly(N-alkyl methacrylamide) derivatives. Then, the use of heavy metal ions in the presence of such functional particles should specifically capture recombinant proteins (i.e., proteins bearing a poly(histidine) part). In order to understand and to optimize the specific capture and the purification of recombinant proteins, various parameters have been investigated as a systematic study. Firstly, the adsorption was investigated as a function of pH and protein concentration. According to high hydration of the prepared nanohydrogel, no marked adsorption was observed. Secondly, the effect of pH was investigated and found to be the driven parameter affecting the metal ions immobilization and the recombinant proteins complexation. As a result, high protein complexation was observed at basic pH compared to non-complexation at acidic pH medium. The immobilized proteins via complexation were released by changing the pH. This decomplexation seems to be effective but depends on fixation conditions and particle surface structure.

Nanophase Separation of Poly(N-alkyl acrylamides): The Dependence of the Formation of Lamellar Structures on Their Alkyl Side Chains

In this study, poly(N-alkyl acrylamides) [(pAlkylAms)], which contain alkyl side chains that differ with respect to the chain length (n; n = 4–18), were synthesized and the formation of lamellar st...

Full and Partial Amidation of Poly(methyl acrylate) as Basis for Functional Polyacrylamide (Co)Polymers

The direct modification of poly(methyl acrylate) (PMA) to obtain functional poly(acrylate ester)s or poly(N-alkyl acrylamide)s is generally considered to be an inefficient approach. Only in recent years, several research groups reported the possibility of the direct modification of unactivated poly(acrylate ester)s in order to obtain functional structures. Within this contribution, we explored the amidation kinetics of PMA with five different amines, utilizing triazabicyclodecene (TBD) as an organocatalyst. We demonstrate that the reaction conditions can be tuned to provide kinetic control over the functionalization degree of the polymer. The reaction kinetics revealed that amine nucleophilicity plays a larger role at the initial stages of the reaction, while steric factors and polymer solvation dominate the reaction kinetics at later stages. Finally, we demonstrate the utility of the developed approach to synthesize functional polymers with olefin side chains, which were subsequently crosslinked via thiol-ene and Alder-ene chemistry.

Isomeric and structural effects in polymer cononsolvent systems

Thermoresponsive poly (N-isopropylacrylamide) (PNIPAM) has many analogs that exhibit cononsolvency behavior in mixtures of water and an alcohol. Cononsolvency is characterized by a combination of good solvents for a polymer that results in decreased solubility. In this work, the cononsolvency behavior of linear PNIPAM, four-arm (4f) star PNIPAM, and linear poly(N-n-propylacrylamide) (PNnPAM), with terminal groups that vary in hydrophobicity, were investigated in mixtures of water and propanol. Polymers were synthesized by RAFT polymerization and subsequently functionalized with one pot aminolysis/thiol-ene chemistry. Turbidimetry measurements and dynamic light scattering (DLS) were used to study the cononsolvency behavior by determining the critical solution temperature (Tc). The measurements show that the size and shape of the hydrophobic region of both the solvent and n-alkyl acrylamide monomer affect Tc and the phase transition behavior. The findings suggest methods to impart multiresponsiveness to soft material systems.

Wide Range of Functionalized Poly(N-alkyl acrylamide)-Based Amphiphilic Polymer Conetworks via Active Ester Precursors

A versatile strategy for the fabrication of functional and nanostructured poly(N-alkyl acrylamide)-based amphiphilic polymer conetworks (APCNs) from hydrophobic precursor networks is presented. The active ester monomer pentafluorophenyl acrylate (PFPA) fulfills a dual role: it provides miscibility with hydrophobic macromonomer cross-linkers and activates the acrylate for amidation reactions. Thereby, it acts as a general hydrophobic masking group for N-alkyl acrylamides, and enables the transformation of PFPA-based hydrophobic precursor networks into a multitude of different poly(N-alkyl acrylamide)-l-PDMS APCNs. These optically transparent APCNs possess nanophase-separated morphologies with domain sizes in the nanometer range. Variation of the amide results in different types of APCNs, despite them being derived from the same precursor network and having identical network structures. Accordingly, the properties of these APCNs can be tailored to the desired application by simple variation of the amide fun...

FT-IR and computer modeling study of hydrogen bonding in N-alkyl acrylamide–toluene binary mixtures

Degree of hydrogen bonding driven self-association of N-(n-butyl)acrylamide, N-(n-octyl)acrylamide, N-(sec-octyl)acrylamide and N-(tert-octyl)acrylamide in toluene was investigated using IR spectroscopy and computer modeling methods.Consistent results were demonstrated in the treatment of the Amide-I (νC=O), Amide-II (δN−H and νC−N) and Amide-A (νN−H) absorption bands in IR spectra. Thus, the content of non-bonded (free) amide groups decreases from 83–98% to 8–20% and the content of linear polyassociates increases to 80–90% with an increase in monomer concentration from 0.5 wt% to 50 wt%. The content of cyclic dimers was equal to the value between 5 and 10% regardless of the initial monomer concentration. Dependences of the association degree and the content of the linear polyassociates on the concentration were found to be similar for all of the studied amides.

Doubly thermo-responsive copolymers in ionic liquid.

We report the behaviour of thermoresponsive block copolymers of n-butyl acrylate and N-alkyl acrylamides in [C2mim][NTf2]. Poly(N-isopropylacrylamide) exhibits an upper critical solution temperature in [C2mim][NTf2] whereas poly(n-butyl acrylate) has a lower critical solution temperature. Consequently, these polymers exhibit double thermo-responsiveness correlated with the macromolecular structure. Moreover, a switching from micellar to reverse micellar structures was induced by a change in temperature. This property enables the development of reversible shuttles between ionic liquids and water.

Platelet repellent properties of hydrogel coatings on polyurethane-coated glass surfaces.

Thromboembolism is a severe complication in patients with ventricular assist devices. Interactions of platelets with the artificial surface and pathological blood flow conditions could contribute to thrombus formation. Previous studies suggested that strongly swellable polymer coatings prepared from various poly(N-alkyl acrylamides) are bioinert as they repel proteins and cells. In this study, we tested structurally similar polymer coatings with varying degrees of crosslinking and swelling to explore if the bioinert character of such coatings is also valid under whole blood perfusion and shear stress. Glass substrates coated with medical grade polyurethane (PU) were modified with surface-attached poly(N-alkyl acrylamide) layers, which differed in crosslinking and in swelling. Slides were perfused with human blood containing fluoresceinated platelets at a shear rate of 1500 s for 3 minutes. Noncoated and PU-coated glass slides served as a reference for thrombogenic surfaces. We detected severe platelet adhesion on the reference surfaces. There was no platelet adhesion on poly(N-alkyl acrylamide) coatings with a swelling factor above 1.5-2 (p < 0.001 compared with PU). A lower swelling factor resulted in severe platelet adhesion. Different degrees of crosslinking ranging from 1% to 10% did not reverse platelet repellent properties of the representative polymer tested (p < 0.001 compared with PU).

Platelet repellent properties of hydrogel coatings on polyurethane coated glass surfaces

Objectives: Thromboembolism is a severe complication in patients with ventricular assist devices (VAD). Interactions of platelets with the artificial surface and pathological blood flow conditions may contribute to thrombus formation. Previous studies postulated that strongly swellable polymers, called hydrogels, are protein and cell repellent. This bio-inert behavior makes hydrogel coatings promising candidates as blood-compatible materials. However, an analysis of these polymer layers under whole blood conditions and shear stress are rare. In our study we systematically tested structurally similar hydrogel coatings belonging to the poly(N-alkyl acrylamide) class under whole blood perfusion and shear stress. The structural variations of the polymers lead to differences in their hydrophilicity and swelling behavior.

The Influence of the Synthesis Conditions on the Compositional Inhomogeneity of Copolymers of Higher N-alkyl Acrylamides and n-docecyl (meth)Acrylate

The “special” nature of the copolymerisation of higher N-alkyl acrylamides of different structure with n-dodecyl acrylate or n-docecyl methacrylate in butyl acetate or toluene is shown. It has been found that the compositional inhomogeneity of the obtained copolymers is determined by the overall initial monomer concentration and the structure of the ester, while the structure of the amides, replacement of the solvent, and variation of the initiator concentration have little effect on compositional inhomogeneity.

Highly efficient synthesis of cylindrical polymer brushes with various side chains via click grafting-onto approach

Though much attention has been paid to synthesis of cylindrical polymer brushes, it is still not easy to prepare well-defined brushes by a general approach. Herein, well-defined cylindrical polymer brushes with various side chains were synthesized via grafting-onto approach by CuAAC click chemistry. Narrowly dispersed polymer backbones functionalized with azide groups were obtained by post-modification of poly(glycidyl methacrylate) (PGMA) which was prepared by reversible addition-fragmentation chain transfer (RAFT) mediated radical polymerization. The alkyne-terminated side chains, polystyrene, polyacrylates, polymethacrylates and poly(N-alkyl acrylamide)s, were synthesized by RAFT mediated radical polymerization with alkyne-containing chain transfer agents (CTAs). The CuAAC reactions between the backbone and side chain polymers were conducted with an equivalent feed of alkyne-terminated side chains and azide groups under mild conditions. Influences of reaction conditions and chemical composition of polymer side chains on grafting efficiency and molecular weight distribution of the polymer brushes were investigated. It is demonstrated that the side chains of polystyrene, polyacrylates and poly(N-alkyl acylamide)s were grafted at a density above 85% while that of polymethacrylates decreased to ca. 50%. The polymer brushes synthesized under the optimized reaction conditions had well-defined chemical composition and narrow distribution of molecular weight, and their wormlike morphology was visualized by atomic force microscopy (AFM).

Homopolymerization of higher alkyl (meth)acrylates and N-alkyl acrylamides in toluene: an effect of monomer self-organization

The kinetics of the free-radical polymerization of 11 higher alkyl acrylates, alkyl methacrylates, and alkyl acrylamides (the alkyl group of C4-C12) has been studied in toluene. The nature of concentration dependences of the reduced initial rate of the polymerization was found to be appreciably affected by the length and degree of the branching of alkyl groups as well as the presence of the methyl substituent in the vinyl fragment. It was shown that the concentration effects observed can not be explained by the change in a viscosity of monomer solutions. The nature of the concentration effects was assumed to be caused by the structure of monomer assemblies.

Nickel-catalyzed coupling reactions of alkenes

Several reactions of simple, unactivated alkenes with electrophiles under nickel(0) catalysis are discussed. The coupling of olefins with aldehydes and silyl triflates provides allylic or homoallylic alcohol derivatives, depending on the supporting ligands and, to a lesser extent, the substrates employed. Reaction of alkenes with isocyanates yields N-alkyl acrylamides. In these methods, alkenes act as the functional equivalents of alkenyl- and allylmetal reagents.

Effect of chemical structure on the volume-phase transition in neutral and weakly charged poly(N-alkyl(meth)acrylamide) hydrogels studied by ultrasmall-angle x-ray scattering

Neutral poly(N-isopropylacrylamide) (PIPAAm), poly(N,N-diethylacrylamide) (PDEAAm), and poly(N-isopropylmethacrylamide) (PIPMAm) hydrogels and their weakly charged counterparts prepared by copolymerizing with sodium methacrylate (x(MNa)=0,0.025,0.05) were studied using ultrasmall-angle x-ray scattering. The volume-phase transition in hydrogels was observed as an increase in the inhomogeneity correlation length of the networks. The change in inhomogeneity correlation length was abrupt in neutral PIPAAm and PIPMAm gels with increase in temperature but was continuous in neutral PDEAAm gels. Addition of ionic comonomer to the network backbone suppressed the volume-phase transition in poly(N-alkylacrylamide)s but not in PIPMAm. The observed differences in temperature-induced volume change of these three polymers in water cannot be rationalized based on their relative hydrophobicity and are instead explained by considering the hydrogen-bonding constraints on their thermal fluctuations. Both PIPAAm and PDEAAm undergo volume collapse since their thermal fluctuations are constrained by hydrogen bonding with water to an extent that beyond a critical temperature they seek entropic compensation. Although thermal fluctuations in both PIPAAm and PIPMAm are equally constrained, thermal energy of the latter can be relaxed via the rotation of alpha-methyl groups allowing it greater flexibility. Compared to N-alkylacrylamides, N-alkylmethacrylamide can thus sustain hydrogen bonding to relatively higher temperatures before seeking entropic compensation by undergoing volume collapse.