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As one of the most critical molecular parameters, molecular weight distribution has a profound impact on the structure and properties of polymers. Quantitative and comprehensive understanding, however, has yet to be established, mainly due to the challenge in the precise control and regulation of molecular weight distribution. In this work, we demonstrated a robust and effective approach to artificially engineer the molecular weight distribution through precise recombination of discrete macromolecules. The width, symmetry, and other characteristics of the distribution can be independently manipulated to achieve absolute control, serving as a model platform for highlighting the importance of chain length heterogeneity in structural engineering. Different from their discrete counterparts, each individual component in dispersed samples experiences a varied degree of supercooling at a specific crystallization temperature. Non-uniform crystal nucleation and growth kinetics lead to distinct molecular arrangements. This work could bridge the gap between discrete and dispersed macromolecules, providing fundamental perspectives on the critical role of molecular weight distribution.

In this work, for the first time, polymer chain growth and topology formation was monitored and quantitatively evaluated using a maleimide-based fluorogenic probe based on a photo-induced electron transfer (PET) mechanism. A fluorene-containing monomer bearing terminal maleimide and thiol functional groups was rationally designed. The fluorescence of fluorene was effectively quenched by the adjacent maleimide group, which was proved by model reactions. Firstly, the correlation between molecular weight and fluorescence intensity was established as a calibration curve using precisely synthesized monodisperse polymers with varying numbers of repeating units via an iterative exponential growth strategy. Secondly, step-growth polymerization of the maleimide–fluorene–thiol monomer progressively consumed the maleimide group during polymer chain propagation and led to a gradual increase of fluorescence. This provides a quantitative and robust approach to monitor polymerization processes in situ. Moreover, cyclic oligomers were produced via intramolecular thiol–maleimide Michael addition in highly diluted solutions of linear precursors, and the cyclization process resulted in gradual enhancements of fluorescence intensity due to the elimination of maleimide groups. The cyclic oligomer content at a determined time can thus be quantitatively calculated based on fluorescence emission, enabling a real-time approach for monitoring/surveilling the cyclization process. We further applied this fluorogenic probe method to quantitatively monitor the formation of polymers with more complicated topologies, such as “cyclic-brush-like” macromolecules. This work demonstrates a facile, robust, and versatile platform for monitoring polymerization processes in situ, which may inspire and facilitate diverse molecular design and preparation in the field of precision polymer synthesis.

Complexation of proteins with polyelectrolytes or block copolymers can lead to phase separation to generate a coacervate phase or self-assembly of coacervate core micelles. However, many proteins do not coacervate at conditions near neutral pH and physiological ionic strength. Here, protein supercharging is used to systematically explore the effect of protein charge on the complex coacervation with polycations. Four model proteins were anionically supercharged to varying degrees as quantified by mass spectrometry. Proteins phase separated with strong polycations when the ratio of negatively charged residues to positively charged residues on the protein (α) was greater than 1.1-1.2. Efficient partitioning of the protein into the coacervate phase required larger α (1.5-2.0). The preferred charge ratio for coacervation was shifted away from charge symmetry for three of the four model proteins and indicated an excess of positive charge in the coacervate phase. The composition of protein and polymer in the coacervate phase was determined using fluorescently labeled components, revealing that several of the coacervates likely have both induced charging and a macromolecular charge imbalance. The model proteins were also encapsulated in complex coacervate core micelles and micelles formed when the protein charge ratio α was greater than 1.3-1.4. Small angle neutron scattering and transmission electron microscopy showed that the micelles were spherical. The stability of the coacervate phase in both the bulk and micelles improved to increased ionic strength as the net charge on the protein increased. The micelles were also stable to dehydration and elevated temperatures.

This paper reports the molecular design and click syntheses of novel shape amphiphiles with molecular architectures beyond conventional giant surfactants. They include (1) the giant bolaform surfactant which consists of a polystyrene (PS) chain tethered with one hydrophilic POSS cage at each end of the chain (DPOSS–PS–DPOSS); (2) the giant gemini surfactant which contains two hydrophilic POSS cages and two PS tails tethered at one junction point (2DPOSS–2PS); and (3) the multi-headed giant surfactant which is composed of three hydrophilic POSS cages tethered at one end of a PS chain (3DPOSS–PS). The syntheses were achieved in a modular and efficient fashion following the sequential click approach in good yields, providing easy access to a family of shape amphiphiles with precise chemical structures and fine-tuned interactions for a systematic study of structure–property relationships.

A series of [60]fullerene (C60)-containing poly(ethylene oxide)-block-polystyrene (PEO-b-PS) with various numbers and different locations of C60 along the polymer chains were designed and synthesized via a combination of “click” chemistry and living/controlled polymerization techniques such as anionic polymerization, atom transfer radical polymerization, and reversible addition–fragmentation chain transfer polymerization. One C60 was tethered either to the end of a PS block (PEO-b-PS-C60) or at the junction point between PS and PEO blocks [PEO-(C60)-PS]; while multiple C60s could be attached randomly along the PS block (PEO-b-PS/C60). The reaction conditions were carefully controlled to ensure a quantitative C60 functionality at precise locations in the case of PEO-b-PS-C60 and PEO-(C60)-PS and to avoid crosslinking in the synthesis of PEO-b-PS/C60. The results have implications in the precision synthesis of fullerene polymers in general. These C60-containing diblock copolymers possess different composition, diverse architecture, and high fullerene functionality. They can serve as model “shape amphiphiles” for the construction of complex hierarchical structures via the interplay between C60–C60 aggregation and block copolymer self-assembly/micro-phase separation.

Precise control of primary chemical structures, especially those of complex structures, is a prerequisite to understand the structure–property relationships of functional macromolecules. In this article, we report the rational design and tandem synthesis of three asymmetric giant gemini surfactants (AGGSs) of complex macromolecular structures based on polyhedral oligomeric silsesquioxane (POSS). In two cascading processes (typically within 5 hours), AGGSs can be synthesized where the length of the two polymer tails and the identity of the two POSS heads can be independently controlled and systematically varied. It represents a convenient, efficient, and modular way to prepare giant molecules with rigorous structural precision in only a few steps. This study expands the scope of synthetically available giant surfactants and facilitates further structural evolution toward even more complex macromolecules.

Convenient synthesis of fluorinated molecular nanoparticles constitutes a major challenge in the preparation of fluoro shape amphiphiles. To facilitate a modular and efficient synthesis, a “clickable” fluorinated polyhedral oligomeric silsesquioxane functionalized with seven 1H,1H,2H,2H-heptadecafluorodecyl side chains and one alkyne group on its periphery (FPOSS-alkyne) was designed and synthesized. It was then used to prepare a series of FPOSS-containing polymers with various architectures via “click” chemistry. FPOSS was tethered onto either homo-polystyrene (PS) or polystyrene-block-poly(ethylene oxide) (PS-b-PEO) at precise locations, including the chain end (FPOSS-PS, FPOSS-PS-b-PEO) or junction point [PS-(FPOSS)-PEO], or distributed randomly along a PS chain (PS/FPOSS). This study demonstrates the chemical robustness of the novel building block and establishes a general and efficient approach to introduce fluorous molecular clusters onto polymers, especially for high molecular weight polymers or those polymers with high fluoro contents. These precisely defined FPOSS-containing polymers could serve as model compounds to study the self-assembly behaviors of these shape amphiphiles in the bulk, solution and thin film.

This paper reports our recent investigations in the synthesis, characterization, and solution self-assembly of giant gemini surfactants consisting of two hydrophilic carboxylic acid-functionalized polyhedral oligomeric silsesquioxane (APOSS) heads and two hydrophobic polystyrene (PS) tails covalently linked via a rigid spacer (p-phenylene or biphenylene) (PS–(APOSS)2–PS). The sequential “click” approach was employed in the synthesis, which involved thiol–ene mono-functionalization of vinyl-functionalized POSS, Cu(I)-catalyzed Huisgen [3 + 2] azide–alkyne cycloadditions for “grafting” polymer tails onto the POSS cages, and subsequent thiol–ene “click” surface functionalization. The study of their self-assembly in solution revealed a morphological transition from vesicles to wormlike cylinders and further to spheres as the degree of ionization of the carboxylic acid groups on POSS heads increases. It was found that the PS tails are generally less stretched in the micellar cores of these giant gemini surfactants than those of the corresponding single-tailed (APOSS–PS) giant surfactant. It was further observed that the PS tail conformations in the micelles were also affected by the length of the rigid spacers where the one with longer spacer exhibits even more stretched PS tail conformation. Both findings could be explained by the topological constraint imposed by the short rigid spacer in PS–(APOSS)2–PS gemini surfactants. This constraint effectively increases the local charge density and leads to an anisotropic head shape that requires a proper re-distribution of the APOSS heads on the micellar surface to minimize the total electrostatic repulsive free energy. The study expands the scope of giant molecular shape amphiphiles and has general implications in the basic physical principles underlying their solution self-assembly behaviors.

Janus particles have attracted significant attention in recent years, due to their potential in nanomanufacturing. Their asymmetric features impart unique physical and chemical properties, which can be tuned and utilized to control their solution-state assembly. While several examples of Janus nanostructures have been reported in the literature, the scientific community continues to pursue synthetic routes which are less time and resource intensive. Herein, we describe a facile method to synthesize Janus nanoparticles in which colloidal micelles template the in situ formation of Au nanoparticles in the shell layer. The resulting morphologies of the hybrid Au–polymer nanoparticles can be adjusted widely by controlling the polymer and reducing agent (HEPES (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid)) concentrations. High-fidelity populations of Au–micelle Janus nanoparticles are obtained when the polymer concentration is high (≥1.0 × 10−6 mmol L−1) and the HEPES concentration is low (≤0.3 mol L−1). Conversely, when the HEPES concentration is high (≥0.5 mol L−1) and the polymer concentration is low (≤2.4 × 10−7 mmol L−1), raspberry-like clusters are formed, where each micelle encumbers several Au nanocrystals. Our method is attractive in that the number of Au nanoparticles on each Au–micelle entity can be controlled using a scalable, aqueous solution process. It also has significant potential for the directed assembly of Au nanoparticle superstructures, as the nature and geometry of the polymer precursors can be varied.