Unique Aggregation Behavior Research Articles

Aggregation of positively charged poly(methyl methacrylate) latex particles in the presence of trifluoromethanesulfonate anion

Abstract We investigated the unique aggregation behavior of 3 types of positively charged poly(methyl methacrylate) (PMMA) latex particles in the presence of a trifluoromethanesulfonate (triflate) anion. The particles were prepared based on surfactant-free emulsion polymerization using azo radical initiators. The triflate anion was strongly adsorbed to surfaces of positively charged PMMA latex particles, as confirmed by electrophoresis. Additionally, its presence significantly reduced the critical coagulation concentration of the cationic PMMA latex particles compared with other anions.

Solution processable Zn-salphen containing π-conjugated polymers with unique aggregation behavior as organic optoelectronic materials

Series of π-conjugated polymers containing electron-withdrawing Zn-Schiff base complex (Zn-salphen) were reported. These polymers can be easily obtained with controllable optical bandgap (Egopt) varying from 1.50 to 2.13 eV by changing the π-conjugated comonomers, and together with excellent thermal stabilities. It was found that the introduction of alkyl chains could provide good solution process-ability for these polymers in chlorobenzene solutions. All the polymers exhibit high hydrophilic characteristics compared to traditional semi-conducting polymers. This is caused by the large polarity of Zn-salphen, which results in strong inter-molecular interactions for the polymers analyzed based on their optical properties. Interestingly, these aggregation behaviors are highly dependent on the type of solvents and coordinating additives such as pyridine, which can be observed from their UV–vis absorption and photoluminescence (PL) spectra. In addition, the film morphologies of these polymers can be modified by using pre- and post-treatments such as thermal annealing, solvent annealing and additives. This work introduces a new strategy for constructing semi-conducting polymers by solving the problem of poor solubility of Zn-salphen complex, and preliminarily studies the feasibility of these Zn-salphen containing polymers regarding their solution process-ability, optical adjustment and morphology optimization. These polymers are considered potential candidates for applications in photoelectric devices.

Alkaline amino acids present unique aggregation behavior for quinoa protein gelation under microwave irradiation

This research focused on the unique aggregation behavior of l-Lysine (L-Lys) and l-Arginine (L-Arg) on quinoa protein (QP) gelation under microwave (MW) irradiation. The results of pH and conductivity manifested that the discrepancy of the influence of two alkaline amino acids on protein was due to the diversity of their electrochemical characteristics rather than to aggregation induced by pH-dominated acid-base transitions. Solubility, turbidity and particle size, ζ-potential results exhibited that L-Lys enhanced the ordered aggregation of protein induced by MW heating more than L-Arg. Circular dichroism (CD), UV absorption spectra, surface hydrophobicity (H0) and sulfhydryl groups demonstrated that L-Lys denaturized and unfolded proteins more vigorously than L-Arg, exposing more hydrophobic residues and boosting the hydrophobicity of the protein's surface. These findings emphasized that L-Lys and MW had a more pronounced synergistic effect on the strength and water holding capacity (WHC) of protein gels than L-Arg. Scanning electron microscopy (SEM) also revealed a denser porous network microstructure in the QP gels with L-Lys added.

Releasing Acceptor from Donor Matrix to Accelerate Crystallization Kinetics with a Second Donor toward High‐Efficiency Green‐Printable Organic Photovoltaics

AbstractThe state‐of‐the‐art power conversion efficiency (PCE) of organic solar cells (OSCs) is typically achieved in the devices fabricated by toxic halogen solvents with complex post‐treatment processes in strictly inert atmosphere. Developing suitable processing method for printing in ambient air using eco‐friendly solvents with continuous solution supply and fabricating efficient devices without any post‐treatment are intensively desired. Controlling the crystallization kinetics to fine‐tune the acceptor's assembly behavior with a second donor for favorable morphological evolution is an effective approach to achieve above requirements. Herein, a kinetics‐controlling strategy is implemented by introducing a strong crystalline small molecule, BTR‐Cl, to enhance the crystallinity of acceptors. The combined in situ spectra characterizations revealed that the earlier aggregation of acceptor and modulation in conformation of PM6 can be achieved. This unique aggregation behavior facilitated enhanced film crystallization with reduced paracrystallinity of π–π stacking, resulting in improved charge transport and inhibited charge recombination. An outstanding PCE of 17.50% is obtained for the device processed with o‐xylene via ambient air printing without any post‐treatment. More significantly, efficient all‐printed inverted devices and large‐area modules are prepared. The generalization of this strategy has been confirmed in other efficient systems, suggesting a great potential for universally fabricating high‐efficiency and eco‐friendly OSCs.

Synthesis and Performance of Double-Chain Quaternary Ammonium Salt Glucosamide Surfactants.

A series of double-chain quaternary ammonium salt surfactants N-[N′[3-(gluconamide)] propyl-N′-alkyl]propyl-N,N-dimethyl-N-alkyl ammonium bromide (CnDDGPB, where n represents a hydrocarbon chain length of 8, 10, 12, 14 and 16) were successfully synthesized from D (+)-glucose δ-lactone, N,N-dimethyldipropylenetriamine, and bromoalkane using a two-step method consisting of a proamine-ester reaction and postquaternization. Their surface activity, adsorption, and aggregation behavior in aqueous solution were investigated via measurements of dynamic/static surface tension, contact angle, dynamic light scattering, and transmission electron microscopy. An analysis of their application performance in terms of wettability, emulsifying properties, toxicity, and antibacterial properties was conducted. The results show that with increasing the carbon chain length of the CnDDGPB surfactants, their critical micelle concentration (CMC) increased and the pC20 and efficiency in the interface adsorption of the target product gradually decreased. Moreover, the influence of the hydrophobic carbon chain length on the surface of polytetrafluoroethylene (PTFE) was even greater for the wetting effect, reducing the contact angle to 32° within the length range of C8–C14. The results of the contact angle change and the wettability experiments proved that C10DDGPB exhibited the best wettability. The liquid paraffin and soybean oil emulsification ability of CnDDGPB showed an upward trend followed by a downward trend with the growth of the carbon chain, with C12DDGPB exhibiting the best emulsification performance. The Dlong/Dshort ratio was far lower than 1, which indicates mixed-kinetic adsorption. The surfactants formed spherical micelles and showed a unique aggregation behavior in aqueous solution, which showed an increase–decrease–increase trend with the change in concentration. A cell toxicity and acute oral toxicity experiment showed that the CnDDGPB surfactants were less toxic than the commonly used surfactant dodecyldimethylbenzyl ammonium chloride (1227). In addition, at a concentration of 150 ppm, CnDDGPB exhibited the same bacteriostatic effect as 1227 at a concentration of 100 ppm. The results demonstrate that sugar-based amide cationic surfactants are promising as environmentally friendly disinfection products.

Synthesis and properties of stellate lactosamide quaternary ammonium surfactants

A number of stellate lactosamide quaternary ammonium salt surfactants (N-dodecyl-N, N-bis[(3-lactosamide) propyl]-N-alkylamine bromide, C n DBLB, where n represents hydrocarbon chain lengths of 12,14 and 16) was successfully synthesized from lactobionic acid, N-(3-aminopropyl)-N-dodecylpropane-1,3-diamine, and bromoalkane by a two-step method comprising a proamine ester reaction and post-quaternization. The surface activity, adsorption, and aggregation behavior of the surfactants in aqueous solutions were investigated by dynamic/static surface tension, contact angle, dynamic light scattering, proton nuclear magnetic resonance spectroscopy, and transmission electron microscopy measurements. The results demonstrated that the equilibrium surface tension ( γ cmc ) of the C n DBLB surfactant was in the range of 28–35 mN/m; thus, it had a strong ability to reduce the surface tension of water. Furthermore, with increase in the carbon chain length of the surfactant, the saturated adsorption amount (Г max ) increased while A min decreased. However, the adsorption duration of C n DBLB was long, and rapid equilibrium could not be achieved on the surface of the solution, indicating a mixed kinetic adsorption mechanism. All three surfactants formed spherical micelles in aqueous solutions. Because the hydrophobic carbon chain length increased, the molecular structure complexity, steric hindrance, and hydrophobic group–water interaction (repulsion) increased, accounting for the unique aggregation behavior of C n DBLB in aqueous solutions. With increase in the concentration of the C 12 DBLB surfactant, the size of the aggregates formed increased. The sizes of the C 14 DBLB and C 16 DBLB aggregates increased initially, decreased, and subsequently increased again. Moreover, the morphology of molecular self-assembly was discussed. C n DBLB surfactant at low concentration was low toxicity or non-toxic, with the increase of concentration, its toxicity will also increase.

Structural and activity changes of xanthine oxidase induced by cetyltrimethylammonium bromide and its Gemini homologue bis(cetyldimethylammonium)hexane dibromide: a comparative study

Interaction of xanthine oxidase (XOD), a key enzyme in purine metabolism, with cetyltrimethylammonium bromide (CTAB) and bis(cetyldimethylammonium)hexane dibromide (C16C6C16Br2) has been studied by employing different techniques at pH 7.4 and 25 °C. The existence of interaction between the surfactants and the enzyme was established by the deviation of tensiometric profiles of surfactants with and without the enzyme. The results obtained by Circular Dichroism, Fluorescence and activity suggest that the Gemini surfactant interacts strongly with the XOD than its conventional homologue. The peculiar structural design of C16C6C16Br2, enhanced ability for electrostatic and hydrophobic interactions, and unique aggregation behavior is accountable for the effectiveness of the Gemini in interacting/unfolding the XOD. The results are contemplated to offer valuable understandings in designing the surfactant-based formulations to moderate the activity of XOD.

Impact of alkyl chain length of temperature-responsive ionic liquids on the aggregation behavior in ionic liquid microemulsions

As is known to all, the alkyl chain is a perfect tool to regulate the microstructure of ionic liquid(IL) microemulsion directly. However, it is still a great challenge to design a new type of temperature-responsive IL with different alkyl chain length to construct the stimulus microemulsion. In this study, a new class of temperature-responsive IL microemulsions was built for the first time, which is composed by [P444,n]Br (n = 8,10,12,14,16,18), [C12mim]Br and H2O. The phase diagram and dynamic light scattering analysis revealed that the size of IL microemulsion droplets can be effective regulated by the alkyl chain length of temperature-responsive IL, so as to gain a series of organized structures. The molecular dynamic(MD) simulations were performed by a series of [P444,n]Br/[C12mim]Br/H2O mixture systems to illustrate this unique aggregation behavior of droplet. Simulation results are presented and discussed via the data of interaction energies, aggregation numbers, radial distribution functions (RDFs) and coordination numbers. The results indicate that the aggregation sizes of [C12mim]+ become smaller with the increase of alkyl chain length of tetrabutylphosphonium cation, which agrees well with experimental results. This is because that the weakened interaction of temperature-responsive IL and water molecules by the long alkyl chain could reduce the electrostatic repulsion of the polarity groups of the surfactants, which may decrease the size of the aggregate. These finding can help in further understanding the structure variation law of temperature-responsive IL microemulsions and thereby improve microemulsion theory.

Novel Modification of Collagen: Realizing Desired Water Solubility and Thermostability in a Conflict-Free Way.

Because of poor water solubility and low thermostability, the application of collagen is limited seriously in fields such as injectable biomaterials and cosmetics. In order to overcome the two drawbacks simultaneously, a novel bifunctional modifier based on the esterification of polyacrylic acid (PAA) with N-hydroxysuccinimide (NHS) was prepared. The esterification degree of PAA-NHS esters was increased upon increasing the NHS dose, which was confirmed by Fourier-transform infrared (FTIR) and nuclear magnetic resonance spectrascopy. FTIR results indicated that the triple helix of the modified collagens remained integrated, whereas the molecular weight became larger, as reflected by the sodium dodecyl sulfate–polyacrylamide gel electrophoresis pattern. The modified collagens displayed excellent water solubility under neutral condition, owing to lower isoelectric point (3.1–4.3) than that of native collagen (7.1). Meanwhile, denaturation temperatures of the modified collagens were increased by 4.8–5.9 °C after modification. The modified collagen displayed hierarchical microstructures, as reflected by field-emission scanning electron microscopy, while atomic force microscopy further revealed a “fishing net-like” network in the nanoscale, reflecting a unique aggregation behavior of collagen macromolecules after modification. As a whole, the PAA-NHS ester as a bifunctional modifier endowed collagen with desired water solubility and thermostability in a conflict-free manner, which was beneficial to the process and application of the water-soluble collagen.

Rational Design of Poly(fluorene)-b-poly(thiophene) Block Copolymers to Obtain a Unique Aggregation Behavior

In poly(thiophene) (PT) block copolymers, aggregation features can be transferred from one block to the other. In this paper, it is investigated whether this is also possible in block copolymers consisting of blocks with different electronic properties, i.e. PT and poly(fluorene) (PF), in order to obtain a polymer with a unique combination of aggregation properties. By combining a PT block with chiral side chains with a PF block with linear octyl side chains, it is probed to obtain a polymer in which chiral expression (arising from the PT with chiral side chains) and β-phase aggregation (arising from the PF with linear octyl side chains) are brought together. This combination is not possible in homopolymers, since chiral aggregation implies chiral, branched side chains and β-phase aggregation is only possible for PF with linear side chains. In a stepwise approach, the right conditions are elucidated to obtain both characteristics in one polymer. For this purpose, three block copolymers were synthesized via Suzuki catalyst transfer condensative polymerization (SCTCP), i.e. , poly(9,9-dioctylfluorene)-b-poly(3-((S)-3,7-dimethyloctyl)thiophene) (POF-b-P3OT*), poly(9,9-dihexylfluorene)-b-poly(3-((S)-3,7-dimethyloctyl)thiophene) (PHF-b-P3OT*), and poly(9,9-dioctylfluorene)-b-poly(3-((S)-2-methylbutyl)thiophene) (POF-b-P3BT*), and their aggregation behavior was studied via solvatochromism experiments. It is concluded that the side chains of the PF block should be 8 C atoms long to ensure maximal β-phase aggregation and that the side chains of the PT block should be short to ensure this block aggregates first in a chiral way. In this way, the PT block can transfer its chirality to the PF block and a polymer is obtained in which β-phase aggregation and expression of chirality are combined in one PF, something which is impossible for homopolymers.

Aggregation Kinetics and Colloidal Stability of Amphiphilic Janus Nanosheets in Aqueous Solution

Although amphiphilic Janus nanosheets have great potential applications in diverse fields to provide improved performance over conventional homogeneous nanoparticles, its aggregation characteristics are still mostly uncovered. Anisotropic shape and chemistry should play a critical role in the interactions between two colloidal particles. Hence, the amphiphilic Janus nanosheets are expected to have unique aggregation behavior different from homogeneous nanoparticles. In this paper, a representative silica-based amphiphilic Janus nanosheets was synthesized, and the influences of temperature, pH, ionic strength, ion valence on their aggregation and stability were probed by batch static multiple light scattering, zeta potential, and electrophoretic mobility measurements. Particularly, the interactions energy between two adjacent amphiphilic Janus nanosheets were calculated based on the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory. The aggregation kinetics and colloidal stability of amphiphilic Janus nanoshe...

Aggregation‐Enhanced Emission of Fluorescent‐Gemini Surfactants with High Photostability for Cell‐Membrane Imaging

Abstract In situ studies of the aggregation behavior of traditional surfactants at the liquid interface using spectroscopic methods are often significantly affected by the large volume of fluorescent groups, such as pyrene. Fluorescent‐Gemini surfactants provide an ideal solution since the fluorescent block can be designed as a spacer or a tail. In this work, we report the synthesis of a new fluorescent‐Gemini surfactant with a rigid spacer (referred to as 8‐TBT‐8). The aggregation behavior and application in cell‐membrane imaging were investigated. The unique aggregation behavior in an organic solvent and aqueous solution was studied using spectroscopy. UV–vis and photoluminescence spectra of 8‐TBT‐8 revealed that this new fluorescent surfactant forms H aggregates in organic solution to give blue emission, whereas it forms J aggregates in aqueous solution to give green fluorescence under UV light. In addition, the fluorescence intensity of 8‐TBT‐8 increases abruptly at concentrations higher than the critical micellization concentration. Good photostability and a unique structure make the synthesized Gemini surfactant very suitable for membrane imaging.

Synthesis of novel d-glucose based anionic bolaamphiphiles and their catalytic application in 1,3-dipolar nitrone cycloaddition reactions

Three d-glucose based bolaamphiphiles have been synthesized by a simple and efficient synthetic methodology utilizing the free C-3 hydroxyl group of diisopropylidene glucose. The resulting bolaamphiphiles showed unique aggregation behavior in aqueous solution, e.g. transformation of vesicle to tubular morphology on aging. The chiral hydrophobic interior of these vesicles was utilized as tiny reaction vessels to carry out 1,3-dipolar nitrone cycloadditions in water. The corresponding isoxazolidine derivatives were formed with high diastereoselectivity in several cases. The bolaamphiphile with 12 carbon spacer (5c) showed better diastereoselectivity among the rest with just 2mol% of catalyst loading and can be reused.

Tallow amphopolycarboxyglycinate-stabilized silver nanoparticles: new frontiers in development of plant protection products with a broad spectrum of action against phytopathogens

Sustainable agriculture calls for minimal use of agrochemicals in order to protect the environment. It has caused an increase in the rate of nanoparticles use, in particular silver nanoparticles (AgNPs) due to their safety for mammals, unique biological activity and a broad spectrum of action against fungal and bacterial pathogens. Until now the use of AgNPs dispersions in the agricultural sector has been essentially limited due to many factors decreased their stability (mixing with other pesticides, presence of electrolytes). We present a versatile synthesis of polyampholyte surfactant (tallow amphopolycarboxyglycinate) stabilized AgNPs. We took a close look at unique aggregation behavior (via dynamic light scattering and UV–vis spectroscopy) and biocidal activity of obtained silver colloids. AgNPs are characterized by exclusively high aggregative stability in the presence of coagulating agents NaNO3 and NaSO4 (up to 1 M), during drying/redispergation, and frost/defrost cycles. The dispersion of AgNPs shows high biocidal activity (EC50 is ten times lower than commercial species ones) with respect to Phytophthora infestans and phytopathogenic fungi. This points to the possibility of successful application of silver preparations within agriculture with the goal of partial reduction of the use of toxic and expensive synthetic antibiotics and pesticides.

Aggregation and thermal gelation of N-isopropylacrylamide based cucurbit[7]uril side-chain polypseudorotaxanes with low pseudorotaxane content

Low pseudorotaxane content (≤3 mol%) endows N-isopropylacrylamide based cucurbit[7]uril polypseudorotaxanes unique aggregation and thermal gelation properties.

Lyotropic Liquid Crystalline Phases of a Phytosterol Ethoxylate in Amide Solvents

Materials exhibiting unique aggregation behavior in nonaqueous solvents have attracted attention due to their wide applications. Motivated by this recent interest, the aggregation properties of a phytosterol ethoxylate surfactant, BPS-10, in three organic amide compounds, formamide (FA), N-methylformamide (NMF), and N,N-dimethyl- formamide (DMF), have been studied. Polarized optical microscopy and small-angle X-ray scattering techniques were used to investigate the lyotropic liquid crystalline (LLC) phases formed in these binary systems. Herein, we discuss the relationship between subtle intermolecular interactions and the aggregation behavior of BPS-10. As good proton donors or acceptors to form hydrogen bonding, FA molecules allow BPS-10 to show a richer phase behavior. Compared with the systems formed in water and ionic liquids, the LLCs constructed in FA have higher thermal stability. In addition, two kinds of lamellar phases could coexist in a narrow region. With the methyl replacement in formamide, however, the ability to form hydrogen bonds is reduced and the solvent bulk phase structure becomes less ordered from FA to DMF. Consequently, the solvophobic interaction of BPS-10 becomes weaker, and the LLCs are more difficult to form. In addition, the extra strong interactions between the steroid rings of BPS-10 may provide enough driving force to produce the hexagonal phase (H1) directly in NMF and DMF without micelle formation, thereby creating a novel sequence (isotropic → H1 → Lα) of ordered phases with increasing surfactant concentration. The results discussed herein should prove to be a useful complement to the growing body of literature regarding steroid surfactant aggregation in polar organic solvents.

Unique Aggregation Behavior of a Carboxylate Gemini Surfactant with a Long Rigid Spacer in Aqueous Solution

A new gemini surfactant with a long and rigid spacer, O,O'-bis(sodium 2-dodecylcarboxylate)-p-dibenzenediol (referred to as C(12)φ(2)C(12)), has been synthesized. Its aggregation in aqueous solution has been studied using static and dynamic light scattering measurements. The homologue O,O'-bis(sodium 2-dodecylcarboxylate)-p-benzenediol (C(12)φC(12)) whose spacer only contains a single phenyl group was also examined for comparison. Dynamic light scattering (DLS) revealed the unexpected existence of large aggregates in the solution of C(12)φ(2)C(12). However, C(12)φC(12) showed rather normal aggregation behavior. Both the results of intrinsic viscosity and light scattering demonstrated a loose structure for the large aggregates of C(12)φ(2)C(12). This behavior was attributed to an extending configuration of C(12)φ(2)C(12) with the two alkyl tails stretching toward the solution due to the rigidity of the long spacer. The large network-like aggregate formation was an inevitable outcome of spontaneously reducing the energy of the system. Freeze-fracture transmission electron microscopy (FF-TEM) images and (1)H NMR measurements supported this speculation. Due to the columnar-like molecular geometry, the large network-like aggregates were directly transformed into rodlike micelles with increasing surfactant concentration. Depending on further micellar growth, the wormlike micelles were finally formed as confirmed by rheological measurements.

Spheres vs. rods: The shape of gold nanoparticles influences aggregation and deposition behavior

The influence of shape on nanomaterial aggregation and deposition was systematically studied with poly-acrylic acid (PAA) coated uniform-sized gold nanospheres (AuNSs) and nanorods (AuNRs). Time resolved dynamic light scattering was employed to study their aggregation kinetics in a wide range of mono- and di-valent electrolyte conditions. Results indicated that PAA coated AuNSs have higher aggregation propensity compared to anisotropic PAA coated AuNRs, as observed through critical coagulation concentration (CCC). The CCC values were estimated as 50mM NaCl and 1.8mM CaCl2 for AuNS, which showed substantial increase to 250mM NaCl and 7mM CaCl2 for anisotropic AuNRs. Though electrokinetic behavior showed similar surface potential for the spherical and rod-shaped materials, the geometric differences between the samples have likely resulted in unique conformation of the PAA coatings, leading to different magnitudes of steric hindrances and hence yielding the observed aggregation behavior. The deposition kinetics was monitored using the quartz crystal microbalance with dissipation technique. AuNRs showed relatively slower deposition compared to AuNSs for low electrolytes concentrations. With the increase in electrolyte concentration, the differences in deposition rates between spheres and rods diminished. The results from this study showed that the shape of nanomaterials can influence interfacial properties and result in unique aggregation and deposition behavior under typical aquatic conditions.

The rheological and structural properties of fish collagen cross-linked by N-hydroxysuccinimide activated adipic acid

Fish skin collagen, with a concentration (6 mg/ml) higher than its critical aggregation concentration (∼0.5 mg/ml), was cross-linked using N-hydroxysuccinimide activated adipic acid (NHS-AA). Dynamic rheological measurement indicated that the storage modulus, loss modulus, complex viscosity and dynamic denaturation temperature increased while the loss tangent decreased with increasing the degree of cross-linking (DC). In addition, collagens with different DC exhibited a significant difference in their activation energies. It was found that collagens with DC in three intervals (DC < ∼25%, ∼25% < DC < ∼50% and DC > ∼50%, respectively) possessed remarkably different rheological behaviors each other. That is, collagens with DC < ∼25% exhibited a liquid-like behavior, while collagens with DC > ∼25% tended to exhibit a solid-like behavior, and especially a sudden loss of flow was observed for collagen with DC > ∼50%. Similar trends were observed from the features in differential scanning calorimetry (DSC) thermograms of collagen. That is, denaturation temperature (Td) was slightly increased and the endothermic peak became broader as DC < ∼25%, Td was increased gradually as DC was further increased, while a sudden increase in Td was observed and the endothermic peak became sharp for collagen with DC > ∼50%. The three-step changes in the rheological behaviors and DSC thermograms of collagens might be due to the unique aggregation behavior of collagen in solution.

Aggregation behavior of organic-soluble semi-aromatic polyimides in N -methylpyrrolidone systems

Aggregation behavior of the organic-soluble semi-aromatic polyimides, whose degrees of imidization range from 69 to 96%, obtained using 4,4′-oxydianiline, 4,4′-diamino-3,3′dihydroxybiphenyl, and bicyclo[2.2.2]-oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BCDA) in N-methylpyrrolidone (NMP), NMP/cyclohexanone, and NMP/γ-butyrolactone (BCDA-based polyimides) were studied by static light scattering (SLS) and dynamic light scattering (DLS). The DLS analyses for the multirelaxation modes demonstrated the specific character unlike flexible polymers that the single BCDA-based polyimide chains first associate with each other to form small clusters in the dilute region, and then expand to large aggregates by the entanglements between the small clusters with an increasing concentration into the semi-dilute region. Given the semi-aromatic structure of BCDA-based polyimides weakening the charge transfer (CT) interaction between the diamine and the dianhydride unit, it is concluded that the unique aggregation behavior of BCDA-based polyimides is dominated by the balance between the driving force for the “organic solubility” given by both the increase in bulkiness and the decrease in the CT interaction, and that for the “organic insolubility” derived from both the hydrogen-bonded interaction of the phenolic hydroxyl groups and the π–π interaction of the phenyl rings. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012