Interpolymer Aggregation Research Articles

Interpolymer association of amphiphilic diblock copolymers bearing pendant siloxane and phosphorylcholine groups

ABSTRACTIn this study, amphiphilic diblock copolymers (PMPCm‐PTSMn) composed of hydrophilic poly(2‐methacryloyloxyethyl phosphorylcholine) (PMPC) and hydrophobic poly(3‐(tris(trimethylsiloxy)silyl)propyl methacrylate) (PTSM) were prepared via RAFT‐controlled radical polymerization. The subscripts m and n represent the degrees of polymerization of the PMPC and PTSM blocks, respectively. Thus, the m/n ratio represents the hydrophilic/hydrophobic balance of the block copolymer. We prepared PMPCm‐PTSMn with m/n ratios of 12, 1.8, and 0.3 and studied their association behaviors in water. PMPCm‐PTSMn with m/n ratios of 12 and 1.8 could dissolve in water. However, PMPCm‐PTSMn with an m/n ratio of 0.3 did not directly dissolve in water. First, PMPCm‐PTSMn with an m/n ratio of 0.3 dissolved in ethanol, whose solution was dialyzed in water to prepare the aqueous solution. The solubilizing state of these polymers in water was examined by light scattering, a fluorescence probe method, and TEM. These polymers took interpolymer aggregation state with various morphologies. The m/n ratios of 12, 1.8, and 0.3 yielded spherical shapes, cylindrical micelles, and vesicle interpolymer aggregate shapes, respectively. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1500–1507

Self-Association Behavior of Cell Membrane-Inspired Amphiphilic Random Copolymers in Water.

Water-soluble and amphiphilic random copolymers (P(MPC/DMAx)) composed of hydrophilic 2-methacryloyloxyethyl phosphorylcholine (MPC) and hydrophobic n-dodecyl methacrylate (DMA) were prepared via reversible addition-fragmentation chain transfer (RAFT) controlled radical polymerization. The compositions of DMA unit (x) in the copolymer were in the range of 0 to 38 unit mol %. The degree of polymerization of P(MPC/DMAx) was adjusted to about 200. Since the monomer reactivity ratios of MPC and DMA are 1.01 and 1.00, respectively, ideal free radical copolymerization occurred. In aqueous solutions, interpolymer aggregation occurred due to the hydrophobic pendant n-dodecyl groups. The aggregation number (Nagg) increased with an increasing x. The mobilities of the DMA and MPC pendant groups in aqueous solutions were restricted, as confirmed by 1H NMR relaxation time measurements, because a part of the MPC units were trapped in the hydrophobic microdomain formed from the pendant n-dodecyl groups. The polarity of the hydrophobic microdomain formed from P(MPC/DMA38) in water was similar to that of ethyl acetate according to fluorescence probe experiments. No specific interactions were found in water between P(MPC/DMAx) and bovine serum albumin because the surface of the interpolymer aggregates contained only hydrophilic MPC units.

Ultrasound- and Thermo-Responsive Ionic Liquid Polymers.

Poly(sodium 2-acrylamido-2-methylpropanesulfonate) (PAMPSNa) was prepared via reversible addition-fragmentation chain transfer (RAFT) radical polymerization. An ionic liquid polymer (PAMPSP4448) was then prepared by exchanging the pendant counter cation from sodium (Na+) to tributyl-n-octylphosphonium (P4448+). We studied the ultrasound- and thermo-responsive behaviors of PAMPSP4448 in water. When the aqueous PAMPSP4448 solution was heated from 5 to 50 °C, the solution was always transparent with 100% transmittance. Unimers and interpolymer aggregates coexisted in water in the temperature range 5–50 °C. Generally, hydrogen bonding interactions are broken as the temperature increases due to increased molecular motion. Above 25 °C, the size of the interpolymer aggregates decreased, because hydrophobic interactions inside them were strengthened by dehydration accompanying cleavage of hydrogen bonds between water molecules and the pendant amide or sulfonate groups in PAMPSP4448. Above 25 °C, sonication of the aqueous solution induced an increase in the collision frequency of the aggregates. This promoted hydrophobic interactions between the aggregates to form larger aggregates, and the aqueous solution became turbid. When the temperature was decreased below 8 °C, hydrogen bonds reformed between water molecules and the pendant amide or sulfonate groups, allowing PAMPSP4448 to redissolve in water to form a transparent solution. The solution could be repeatedly controlled between turbidity and transparency by sonication and cooling, respectively.

Solution Properties of Amphoteric Random Copolymers Bearing Pendant Sulfonate and Quaternary Ammonium Groups with Controlled Structures.

Amphoteric random copolymers P(AMPS/APTAC50) x, where x = 41, 89, and 117, composed of sodium 2-acrylamido-2-methylpropanesulfonate (AMPS) and 3-acrylamidopropyltrimethylammonium chloride (APTAC) were prepared via reversible addition-fragmentation chain transfer radical polymerization. P(AMPS/APTAC50) x can dissolve in pure water to form small interpolymer aggregates. In aqueous solutions of NaCl, P(AMPS/APTAC50) x can dissolve in the unimer state. Amphoteric random copolymer P(AMPS/APTAC50)c with high molecular weight was prepared via conventional free-radical polymerization. Although P(AMPS/APTAC50)c cannot dissolve in pure water, it can dissolve in aqueous solutions of NaCl. In amphoteric random copolymers with high molecular weight, the possibility of continuous sequences of monomers with the same charge may increase, which may cause strong interactions between polymer chains. When fetal bovine serum (FBS) and polyelectrolytes were mixed in phosphate-buffered saline, the hydrodynamic radius and light-scattering intensity increased. There was no interaction between P(AMPS/APTAC50) x and FBS because corresponding increases could not be observed.

Mesoscopic Structural Aspects of Ca2+-Triggered Polymer Chain Folding of a Tetraphenylethene-Appended Poly(acrylic acid) in Relation to Its Aggregation-Induced Emission Behavior

We recently reported that tetraphenylethene-appended poly(acrylic acid) derivatives [PAA-TPEx (x = 0.01–0.05)] provide a fluorescent Ca2+ sensor, where aggregation-induced emission (AIE) of the TPE pendants occurs in conjunction with Ca2+-triggered polymer-chain folding. On the basis of dynamic and static light-scattering data, here we discuss the hydrodynamic radius and molar mass of PAA-TPE0.01 in the presence of Ca2+, Mg2+, or Na+ at various concentrations and elucidate the origin of the Ca2+ selectivity. In contrast to Na+, which exclusively triggered nonfluorescent interpolymer aggregation of PAA-TPE0.01, Ca2+ and Mg2+ induced polymer-chain folding associated with AIE from the TPE pendants. Importantly, Ca2+ caused polymer-chain folding more effectively than Mg2+. Consequently, polymer aggregates formed in the presence of Ca2+ possessed a much higher inner density than those formed in the presence of Mg2+, leading to a more pronounced AIE behavior and, in turn, the Ca2+ ion selectivity over Mg2+.

Conjugated polyelectrolyte-Ag+ fluorescent switch for biothiol sensing

A new “off-on” switch for sensitive and selective fluorescence detection of biothiols[glutathione(GSH), cysteine(Cys) and homocysteine(Hcy)] was developed based on an anionic conjugated polyelectrolyte(CPE), pyridyl-functionalized poly(phenylene ethynylene)(P1). The fluorescence of P1 can be significantly quenched by Ag+ due to complexation-mediated interpolymer aggregation. Furthermore, biothiols can efficiently recover the fluorescence intensity of P1 as a result of the stronger binding between thiol group and Ag+, which dissociates P1 from the P1/Ag+ complex and disrupts interpolymer aggregation. Under optimum conditions, a good linear relationship in a range of 100–4200 nmol/L is obtained for GSH with a detection limit of 80 nmol/L(S/N=3). As a result of specific interaction between the thiol group and Ag+, the proposed method shows a high selectivity for biothiols. In addition, the CPE-based fluorescence “off-on” switch has been used to quantitatively detect total biothiols in cell lysates.

Aggregation Properties of a Novel Class of Amphiphilic Cationic Polyelectrolytes Containing Gemini Surfactant Segments

A novel class of amphiphilic cationic polyelectrolytes, poly(A-co-G)s, comprising of gemini type surfactant segment 1,3-bis(N,N-dimethyl-N-dodecylammonium)-2-propylacrylate dibromide (G) and acryloyloxyethyl trimethyl ammonium chloride (A), were synthesized. Their aggregation properties were investigated by employing fluorescence spectroscopy, dynamic light scattering, transmission electron microscopy, and ζ-potential measurements. For comparison, a series of polyelectrolytes containing a traditional single alkyl chain surfactant unit (acryloyloxyethyl-N,N-dimethyl-N-dodecylammonium bromide (D)), poly(A-co-D)s, were also synthesized and investigated. It was found that the critical aggregation concentration (cac) of poly(A-co-G)s is much lower than that of poly(A-co-D)s. The huge interpolymer aggregates (with a hydrodynamic radius of >450 nm) occur in poly(A-co-G)s aqueous solution, and the size of aggregates increases with the increase of the molar content of the gemini-type surfmer segment and the concentration of the copolymer. The size of aggregates in poly(A-co-D)s aqueous solution is much smaller than poly(A-co-G)s, which also increases with the increase of the molar content of the single alkyl chain surfmer segment and the concentration of the copolymer. The results of aggregation number and charge density of aggregate in poly(A-co-G)s and poly(A-co-D)s indicate that the copolymers have a strong tendency toward interpolymer aggregation and the aggregates in poly(A-co-G)s are much more compact than those of poly(A-co-D)s. These results are interpreted in terms of the synergistic effects of double hydrophobic chains on the gemini surfactant unit.

A fluorescent conjugated polymer for trace detection of diamines and biogenic polyamines

The aggregation-based trace detection of diamines and biogenic polyamines has been developed utilizing a carboxylic acid-functionalized polyfluorene (PFCOOH-BT5) containing benzo[2,1,3]thiadiazole (BT). Upon addition of diamines or biogenic polyamines, the PFCOOH-BT5 can be cross-linked via electrostatic interactions between the polymer carboxylic acid binding sites and the amino groups of the multiamines to form interpolymer aggregation, which leads to more efficient FRET from fluorene segments to BT units and thus a noticeable fluorescence color change from blue to orange. In contrast, addition of 1,3-propanediol does not lead to significant variations in the photoluminescence spectra of PFCOOH-BT5. This unique fluorescence response from PFCOOH-BT5 to diamines and biogenic polyamines can achieve a detection concentration as low as 2 μM, indicating that PFCOOH-BT5 can serve as a general and effective chemosensor to detect trace diamines and biogenic polyamines.

Synthesis of thermo‐responsive 4‐arm star‐shaped porphyrin‐centered poly(N,N‐diethylacrylamide) via reversible addition‐fragmentation chain transfer radical polymerization

AbstractTetrafunctional porphyrins‐containing trithiocarbonate groups were synthesized by an ordinary esterification method. This tetrafunctional porphyrin (TPP‐CTA) could be used as a chain transfer agent in a controlled reversible addition‐fragmentation chain transfer (RAFT) radical polymerization to prepare well‐defined 4‐arm star‐shaped polymers. N,N‐Diethylacrylamide was polymerized using TPP‐CTA in 1,4‐dioxane. Poly(N,N‐diethylacrylamide) (PDEA) is known to be a thermo‐responsive polymer, and exhibits a lower critical solution temperature (LCST) in water. The star‐shaped PDEA polymer (TPP‐PDEA) was therefore also thermo‐responsive, as expected. The LCST of this polymer depended on its concentration in water, as confirmed by turbidity, dynamic light scattering (DLS), static light scattering (SLS), and 1H NMR measurements. The porphyrin cores were compartmentalized in PDEA shells in aqueous media. Below the LCST, the fluorescence intensity of TPP‐PDEA was about six times larger than that of a water‐soluble low molecular weight porphyrin compound (TSPP), whose fluorescence intensity was independent of temperature. Above the LCST, the fluorescence intensity of TPP‐PDEA decreased, while the intensity was about three times higher than that of TSPP. These observations suggested that interpolymer aggregation occurred due to the hydrophobic interactions of the dehydrated PDEA arm chains above the LCST, with self‐quenching of the porphyrin moieties arising from these interactions. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009

Effects of pairwise, donor–acceptor functional groups on polymer solubility, solution viscosity and mist control

Homologous series of functionalized polymers were used to compare the solution properties of donor–acceptor (DA) interpolymer mixtures with those of self-associating and non-associating polymer analogues. Polymer analogous synthesis was used to produce a series of polymers from a specific, anionically-polymerized prepolymer (1250 kg/mol polybutadiene), using thiol-ene coupling to incorporate systematically-varied contents of side groups: either tertiary amines (as proton acceptors) or carboxylic acids (both as proton donors in donor–acceptor mixtures, or as self-associating moieties in single-polymer solutions). Comparison with controls reveals that, relative to the effects of self-associations, DA interpolymer interactions more strongly affect solution properties such as phase behavior, interpolymer aggregation, shear viscosity, and elastic response in extensional flow. Specifically, DA associations lead to (i) greater reductions in polymer solubility in hydrocarbon solvents, (ii) interpolymer aggregation into larger clusters, and (iii) greater shear viscosity in solution. Nevertheless, DA associations reduced solution elasticity and mist suppression—a highly unanticipated result in light of the prior literature.

Study on radiation‐induced grafting of hydrophilic monomers onto chitosan

AbstractThe graft polymerization of 2‐Hydroxyethyl acrylate, 2‐Hydroxyethyl methacrylate, and N‐vinylpyrrolidone onto chitosan in aqueous solution initiated by γ‐ray irradiation was carried out. The effect of various conditions such as the absorbed dose, concentration of monomer, and solvent on grafting was investigated. The grafting yield increased with the increase in absorbed dose. The degree of grafting increased with increase in the radiation dose. The obtained graft copolymers showed the solubility in water in wide pH interval. The interactions between grafted chitosan copolymers with sodium dodecyl sulfate (SDS) were studied in an aqueous solution. It was found that there is a narrow molar ratio of SDS/cation (∼ 0.40–0.70) depending on different grafted copolymers, at which the turbidity of SDS‐grafted chitosan complex has a maximum due to the formation of water insoluble interpolymer aggregates via the SDS attached on the polymer chain. The turbidity falls sharply with the further addition of excessive SDS, which forms micelle in the solution and causes the de‐aggregation of the interpolymer aggregates and also because of the precipitation of complexes and returns to the original level. The morphologic properties of thin films of SDS‐ grafted chitosan complex were investigated. It was observed that upon heating the insoluble complex of SDS and grafted chitosan in water, superstructures were formed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Anomalous Transition in Aqueous Solutions of a Thermoresponsive Amphiphilic Diblock Copolymer

The influence of shear flow on aggregation and disaggregation in aqueous solutions of the thermoresponsive methoxy-poly(ethylene glycol)-block-poly(N-isopropylacrylamide) (MPEG53-b-PNIPAAM113) copolymer that exhibits a lower critical solution temperature was investigated with the aid of turbidity, shear viscosity, and rheo small angle light scattering (rheo-SALS) methods. The turbidity results at quiescent conditions revealed a novel transition peak in the turbidity curve at intermediate temperatures, which reflects the delicate interplay between temperature-induced aggregation and shrinking of the species. A similar anomalous transition peak (located at the same temperature) was observed in the steady shear viscosity measurements at intermediate temperatures, and the amplitude of the peak was reduced with increasing shear rate as a consequence of breakup of interaggregate chains. At low temperatures (low sticking probability), enhanced shear rate generated interpolymer aggregates; whereas in the high-temperature domain (high sticking probability) association structures were broken up as the shear rate was increased. The rheo-SALS experiments disclosed growth of aggregates at low temperatures and destruction of association complexes at high temperatures. An increase of the cloud point temperature with rising shear rate is reported, which is interpreted as being a disruption of clusters under the influence of shear stresses.

Macromolecular Recognition by Polymer‐Carrying Cyclodextrins: Interaction of a Polymer Bearing Cyclodextrin Moieties with Poly(acrylamide)s Bearing Aromatic Side Chains

AbstractSummary: The interaction of a polymer bearing β‐cyclodextrin moieties (β‐CD polymer) with poly(acrylamide)s bearing aromatic side chains was investigated by viscometry to study the effect of collectivity (i.e., interactions at multi‐sites) in macromolecular recognition. The formation of inclusion complexes at multi‐sites caused a large difference in the size of interpolymer aggregates, even though the difference in association constants for complexation of native β‐CD with guest moieties was not very much large.Conceptual illustration for interpolymer aggregates of β‐CD polymer with poly(acrylamide)s bearing naphthyl groups substituted on the (a) 1‐ and (b) 2‐positions (see Scheme 1).magnified imageConceptual illustration for interpolymer aggregates of β‐CD polymer with poly(acrylamide)s bearing naphthyl groups substituted on the (a) 1‐ and (b) 2‐positions (see Scheme 1).

Interaction of main chain cationic polyelectrolyte with sodium dodecyl sulfate

The interaction of x, y-ionene ( x=2,4,6; y=4,6,12) polycations with sodium dodecyl sulfate (SDS) has been investigated in aqueous solution. It was found that there is a narrow molar ratio of SDS/cation (∼1.0–1.35) depending on different ionenes, at which the viscosity of ionene–SDS aqueous solution rises suddenly due to the formation of water soluble inter-polymer aggregates via the SDS attached on the polymer chains. The viscosity falls sharply with further addition of excessive SDS, which forms micelle in solution and causes the de-aggregation of the inter-polymer aggregates. The x, y values of the ionene, the polymer concentration and the SDS/cation ratio play a key role in determining the viscosity behavior. At the higher concentration of ionene a gelation occurs suddenly from solution at a specific molar ratio of SDS/cation and was confirmed to be reversible. The viscosity increase and gel formation in ionene–SDS aqueous solution were considered to be related closely with presence of the hydrophobic domain. Using N, N-dimethylflavon as fluorescent probe, the existence of hydrophobic domain in solution has been verified, the hydrodynamic radius of the aggregates in the viscose solution was determined with laser light scattering and an explanation for the viscosity change as well as the gel formation has been proposed.

Interpolymer Association of Cholesterol Pendants Linked to a Polyelectrolyte As Studied by Quasielastic Light Scattering and Fluorescence Techniques

The association behavior of random copolymers of sodium 2-(acrylamido)-2-methylpropanesulfonate (AMPS) and cholesteryl 6-methacryloyloxyhexanoate (Chol-C5-MA) in 0.1 M NaCl aqueous solutions was investigated by quasielastic light scattering and fluorescence techniques to gain further insights into the structures and properties of their “intermolecularly bridged flower-type micelles” which we had proposed previously. When the Chol-C5-MA content in the copolymer was as low as 1 mol %, unimers were found to coexist with the interpolymer aggregates independent of the polymer concentration (CP) in a range 0.1 < CP < 10 g/L. However, when the Chol-C5-MA content was increased to 5 mol %, virtually all the polymer chains form multipolymer aggregates which can be viewed as an assembly of flower-type micelles where polymer chains are “cross-linked” via Chol associations. The aggregation number of Chol moieties was estimated to be 17−19 for the copolymer of 5 mol % Chol-C5-MA by a time-resolved fluorescence quenchin...

Photophysical and Solution Properties of Naphthalene-Labeled Styrene/N,N-Dimethyl Maleimido Propylammonium Propane Sulfonate Copolymer

The photophysical and solution properties of naphthalene-labeled styrene/N,N-dimethyl maleimido propylammonium propane sulfonate copolymer, poly(SDMPAPS)/NA, were studied in terms offluorescence, cloud point, and viscosity measurements. The ratio of intensities of the excimer and monomer fluorescence (I E /I M ) was shown as a function of polymer concentration in deionized water. The value of I E /I M decreases with an increase in the salt concentration. The addition of anionic surfactants to the aqueous solution of poly(SDMPAPS)/NA can either induce or break the interpolymer aggregation. When the electrolyte concentration increases, the Stern-Volmer quenching constant (K sv ) also increases. The phase behavior of poly(SDMPAPS)/NA shows an upper critical solution temperature around 17 °C. The intrinsic viscosity of the poly(SDMPAPS)/NA in the presence of different salts reflects the influence of these salts on the hydrodynamic volume of the polymer chain for poly(SDMPAPS)/NA. A model of the interaction between poly(SDMPAPS)/NA and surfactant in aqueous solution is proposed.

Water-Soluble Copolymers. 62. Nonradiative Energy Transfer Studies of pH- and Salt-Responsive Associations in Hydrophobically Modified, Hydrolyzed Maleic Anhydride-Ethyl Vinyl Ether Copolymers

A series of labeled, hydrophobically modified polymers based on the alternating copolymer of maleic anhydride and ethyl vinyl ether (MAEVE) has been synthesized to specifically address the issue of differences in domain organization of closed, polysoap systems and open, associative-thickening systems. Modification was achieved by reaction of primary amines with MAEVE in organic solvent and hydrolysis in aqueous base. This unique method allows stoichiometic modification with hydrophobic and fluorescent groups. Intramolecular associations predominate in a wide range of environments. The extent to which these interactions occur is effectively probed by monitoring nonradiative energy transfer (NRET) between naphthalene and pyrene groups covalently bound to the polymer chain. Intrapolymer NRET quantum efficiency increases with decreasing pH as the chain contracts to a globular conformation. Interpolymer NRET is independent of salt concentration, but intrapolymer NRET steadily increases with [NaCl] as the shielding of charge-charge repulsions constricts the coil. In extremely acidic and basic environments, interpolymer NRET increases as electrostatic repulsions are shielded or eliminated. A mechanism has been proposed whereby the compaction of labeled polymer micelles results in an enhancement in interpolymer aggregation due to the formation of hydrophobic micellar surfaces.

Observations of the coil—globule transition in single polymers

Abstract We report observations of the coil-globule transition of a single polymer chain in solution. For polyacrylamide (MW = 5−6×106), the transition occurs when the acetone concentration of the acetone water solvent is increased. In polystyrene (MW = 26×106)—cyclohexane solutions, the transition is induced by lowering the temperature. Since the transition to the globule state is in competition with inter-polymer aggregation, measurements must be made at very low polymer concentrations. By measuring the angular dependence of the time-dependent and time-independent parts of the correlation function of light scattered from dilute solutions of polymer (<.1 μg/m1), we have determined the radius of gyration and hydordynamic radius of the globule state before the onset of aggregation.