Toluene

Example 22

To a four-necked flask (1 L volume) equipped with stirring blades, a thermometer, a dropping funnel and a condenser tube, 500 mL of toluene, 30.6 g (0.11 mol) of 4,4′-(propane-2,2-diyl)bis(isocyanate-benzene), and 63.1 mg of p-methoxyphenol were added and dissolved. Next, 14.3 g (0.11 mol) of 2-hydroxyethyl methacrylate was weighed in a beaker, 150 mL of toluene was added, and the mixture was stirred thoroughly and transferred to a dropping funnel. The four-necked flask was immersed in an oil bath heated to 80° C., and 2-hydroxyethyl methacrylate was added dropwise with stirring. After completion of the dropwise addition, the reaction was continued while maintaining the temperature of an oil bath for 24 hours, leading to aging. After completion of the aging, the four-necked flask was removed from the oil bath and the reaction product was returned to room temperature, and then HPLC and FT-IR measurements were performed. Analysis conditions of the HPLC measurement are as follows: a column of ZORBAX-ODS, acetonitrile/distilled water of 7/3, a flow rate of 0.5 mL/min, a multi-scanning UV detector, an RI detector and an MS detector. The FT-IR measurement was performed by an ATR method. As a result of the HPLC measurement, the raw materials 4,4′-(propane-2,2-diyl)bis(isocyanate-benzene) and 2-hydroxyethyl methacrylate disappeared and a new peak of 2-(((4-(2-(4-isocyanate-phenyl)propane-2-yl)phenyl)carbamoyl)oxy)ethyl methacrylate (molecular weight 408.45) was confirmed. As a result of FT-IR measurement, a decrease in isocyanate absorption intensity at 2280-2250 cm⁻¹ and a disappearance of hydroxy group absorption near 3300 cm⁻¹ were confirmed, and a new absorption attributed to urethane group at 1250 cm⁻¹ was confirmed. Next, to a toluene solution containing 40.8 g (0.10 mol) of the precursor compound synthesized in the above procedure, 22.2 g (0.10 mol) of 3-(triethoxysilyl)propan-1-ol was added dropwise with stirring. The reaction was performed with the immersion in an oil bath heated to 80° C. in the same way as in the first step. After completion of the dropwise addition, the reaction was continued for 24 hours, leading to aging. After completion of the aging, HPLC and FT-IR measurements were performed. As a result of the HPLC measurement, the peaks of the raw materials 2-(((4-(2-(4-isocyanate-phenyl)propane-2-yl)phenyl)carbamoyl)oxy)ethyl methacrylate and 3-(triethoxysilyl)propan-1-ol disappeared and 2-(((4-(2-(4-(((3-(triethoxysilyl)propoxy)carbonyl)amino)phenyl)propan-2-yl)phenyl)carbamoyl)oxy)ethyl methacrylate (molecular weight 630.81) was confirmed. As a result of FT-IR measurement, a disappearance of isocyanate absorption at 2280-2250 cm⁻¹ and a disappearance of hydroxy group absorption near 3300 cm⁻¹ were confirmed. The chemical structure formula of the compound synthesized in this synthetic example are described below.

[Figure (not displayed)]

Example 1

This example describes an exemplary nanostructure (i.e. nanocomposite tecton) and formation of a material using the nanostructure.

A nanocomposite tecton consists of a nanoparticle grafted with polymer chains that terminate in functional groups capable of supramolecular binding, where supramolecular interactions between polymers grafted to different particles enable programmable bonding that drives particle assembly (FIG. 4). Importantly, these interactions can be manipulated separately from the structure of the organic or inorganic components of the nanocomposite tecton, allowing for independent control over the chemical composition and spatial organization of all phases in the nanocomposite via a single design concept. Functionalized polystyrene polymers were made from diaminopyridine or thymine modified initiators via atom transfer radical polymerization, followed by post-functionalization to install a thiol group that allowed for particle attachment (FIG. 5). The polymers synthesized had three different molecular weights (˜3.7, ˜6.0, and ˜11.0 kDa), as shown in FIG. 6, with narrow dispersity (Ð<1.10), and were grafted to nanoparticles of different diameters (10, 15, 20, and nm) via a “grafting-to” approach.

Once synthesized, nanocomposite tectons were functionalized with either diaminopyridine-polystyrene or thymine-polystyrene were readily dispersed in common organic solvents such as tetrahydrofuran, chloroform, toluene, and N,N′-dimethylformamide with a typical plasmonic resonance extinction peak at 530-540 nm (FIG. 7A) that confirmed their stability in these different solvents. Upon mixing, diaminopyridine-polystyrene and thymine-polystyrene coated particles rapidly assembled and precipitated from solution, resulting in noticeable red-shifting, diminishing, and broadening of the extinction peak within 1-2 minutes (example with 20 nm gold nanoparticles and 11.0 kDa polymers, FIG. 7B). Within 20 minutes, the dispersion appeared nearly colorless, and large, purple aggregates were visible at the bottom of the tube. After moderate heating (˜55° C. for ˜1-2 minutes for the example in FIG. 7B), the nanoparticles redispersed and the original color intensity was regained, demonstrating the dynamicity and complete reversibility of the diaminopyridine-thymine directed assembly process. Nanocomposite tectons were taken through multiple heating and cooling cycles without any alteration to assembly behavior or optical properties, signifying that they remained stable at each of these thermal conditions (FIG. 7C).

A key feature of the nanocomposite tectons is that the sizes of their particle and polymer components can be easily modified independent of the supramolecular binding group's molecular structure. However, because this assembly process is driven via the collective interaction of multiple diaminopyridine and thymine-terminated polymer chains, alterations that affect the absolute number and relative density of diaminopyridine or thymine groups on the nanocomposite tecton surface impact the net thermodynamic stability of the assemblies. In other words, while all constructs should be thermally reversible, the temperature range over which particle assembly and disassembly occurs should be affected by these variables. To better understand how differences in nanocomposite tecton composition impact the assembly process, nanostuctures were synthesized using different nanoparticle core diameters (10-40 nm) and polymer spacer molecular weights (3.7-11.0 kDa), and allowed to fully assemble at room temperature (˜22° C.) (FIG. 8). Nanocomposite tectons were then monitored using UV-Vis spectroscopy at 520 nm while slowly heating at a rate of 0.25° C./min, resulting in a curve that clearly shows a characteristic disassembly temperature (melting temperature, T_m) for each nanocomposite tecton composition.

From these data, two clear trends can be observed. First, when holding polymer molecular weight constant, T_m increases with increasing particle size (FIG. 8A). Conversely, when keeping particle diameter constant, T_m drastically decreases with increasing polymer length (FIG. 8B). To understand these trends, it is important to note that nanocomposite tecton dissociation is governed by a collective and dynamic dissociation of multiple individual diaminopyridine-thymine bonds, which reside at the periphery of the polymer-grafted nanoparticles. The enthalpic component of nanocomposite tecton bonding behavior is therefore predominantly governed by the local concentration of the supramolecular bond-forming diaminopyridine and thymine groups, while the entropic component is dictated by differences in polymer configuration in the bound versus unbound states.

All nanocomposite tectons possess similar polymer grafting densities (i.e. equivalent areal density of polymer chains at the inorganic nanoparticle surface, FIG. 9) regardless of particle size or polymer length. However, the areal density of diaminopyridine and thymine groups at the periphery of the nanocomposite tectons is not constant as a function of these two variables due to nanocomposite tecton geometry. When increasing inorganic particle diameter, the decreased surface curvature of the larger particle core forces the polymer chains into a tighter packing configuration, resulting in an increased areal density of diaminopyridine and thymine groups at the nanocomposite tecton periphery; this increased concentration of binding groups therefore results in an increased T_m, explaining the trend in FIG. 8A.

Conversely, for a fixed inorganic particle diameter (and thus constant number of polymer chains per particle), increasing polymer length decreases the areal density of diaminopyridine and thymine groups at the nanocomposite tecton periphery due to the “splaying” of polymers as they extend off of the particle surface, thereby decreasing T_m in a manner consistent with the trend in FIG. 8B. Additionally, increasing polymer length results in a greater decrease of system entropy upon nanocomposite tecton assembly, due to the greater reduction of polymer configurations once the polymer chains are linked via a diaminopyridine-thymine bond; this would also be predicted to reduce T m. Within the temperature range tested, all samples were easily assembled and disassembled via alterations in temperature. Inorganic particle diameter and polymer length are therefore both effective handles to control nanocomposite tecton assembly behavior.

Importantly, because the nanocomposite tecton assembly process is based on dynamic, reversible supramolecular binding, it should be possible to drive the system to an ordered equilibrium state where the maximum number of binding events can occur. The particle cores and polymer ligands are polydisperse (FIG. 10) and ordered arrangements represent the thermodynamically favored state for a set of assembled nanocomposite tectons. When packing nanocomposite tectons into an ordered lattice, deviations in particle diameter would be expected to generate inconsistent particle spacings that would decrease the overall stability of the assembled structure. However, the inherent flexibility of the polymer chains should allow the nanocomposite tectons to adopt a conformation that compensates for these structural defects. As a result, an ordered nanocomposite tecton arrangement would still be predicted to be stable if it produced a larger number of diaminopyridine-thymine binding events than a disordered structure and this increase in binding events outweighed the entropic penalty of reduction in polymer chain configurations.

To test this hypothesis, multiple sets of assembled nanocomposite tectons were thermally annealed at a temperature just below their T_m, allowing particles to reorganize via a series of binding and unbinding events until they reached the thermodynamically most stable conformation. The resulting structures were analyzed with small angle X-ray scattering, revealing the formation of highly ordered mesoscale structures where the nanoparticles were arranged in body-centered cubic superlattices (FIG. 11). The body-centered cubic structure was observed for multiple combinations of particle size and polymer length, indicating that the nanoscopic structure of the composites can be controlled as a function of either the organic component (via polymer length), the inorganic component (via particle size), or both, making this nanocomposite tecton scheme a highly tailorable method for the design of future nanocomposites.

Example 151

[Figure (not displayed)]

To a solution of compound 662 (0.270 g, 0.177 mmol, 1.0 eq.) in DCM (6.0 mL) at r.t. was added TFA (2.0 mL) and stirred for 4 h. The mixture was diluted with anhydrous toluene and concentrated, this operation was repeated for three times to give yellow oil, which was purified on prep-HPLC (C₁₈ column, mobile phase A: water, mobile phase B: acetonitrile, from 10% of B to 80% of B in 60 min). The fractions were pooled and lyophilized to give the title compound (172 mg, 83% yield). ESI m/z calcd for C₅₇H₉₀N₁₁O₁₃S [M+H]⁺: 1168.6, found: 1168.6.