Properties Of Supramolecular Polymers Research Articles

Crystallization, recrystallization and melting behaviors in supramolecular poly(l-lactic acid) bonded by metal-ligand coordination

The effect of metal-ligand coordination on crystallization and melting behaviors of polymers has not been comprehensively investigated. In this study, a series of supramolecular poly(l-lactic acid)s (SM-PLLAs) were prepared by changing various metal ions, length of polymer chains and stoichiometric ratio of ligands to metal ions (L/M). The complexation of metal ions with ligands in SM-PLLAs was confirmed by the intrinsic viscosity and UV–visible spectroscopy. It was found that crystallization rate and crystallinity of SM-PLLAs were strongly dependent on the chain length of precursor in both non-isothermal and isothermal crystallizations. With chain length of 1.6 kg/mol, crystallization of PLLA was completely suppressed regardless of the metal ions, whereas PLLA with longer chain length of 3.0 kg/mol exhibited strong dependence of the type of metal. During the heating process, melting behaviors can be tuned by the strength of metal-ligand coordination, temperature and the degree of complexation. Unlike PLLA precursor and SM-PLLA coordinated with Cu2+ exhibited multiple melting behaviors, only a single melting peak was appeared in PLLA bonded with Co2+, indicative of suppression of recrystallization during heating. With ratio of ligand to Co2+ increased from 1:1 to 6:1, crystallization and melting behaviors were tuned by the content of free and bounded PLLA chains. As compared to Cu2+, SM-PLLA coordinated with Co2+ exhibited higher complex modulus and viscosity due to the high bond strength, as well as a more stable structure underwent heating and shear, making diffusion of polymer chains and the structural adjustment more difficult. This work may shed light on understanding the intricate interplay of metal-ligand coordination effects on the crystallization and melting behaviors of polymers, which may be helpful with the design and making out the relationship between structure and properties of supramolecular polymers.

A Strategy Based on Aggregation-Induced Ratiometric Emission to Differentiate Molecular Weight of Supramolecular Polymers.

Molecular weight has an important bearing on the properties of supramolecular polymers. However, the intuitive differentiation of the molecular weight of supramolecular polymers remains challenging. Given this situation, establishing a reliable relationship between fluorescence properties and molecular weight may be a promising strategy. Herein, we prepared a supramolecular monomer M1 with aggregation-induced ratiometric emission characteristics. With the increasing M1 concentration (0.100-100 mM), the average degree of polymerization (DPDOSY ) rose from 1.00 to 293. Meanwhile, the color changed from dark blue to cyan, finally to yellow-green in the same concentration range. Hence, the intuitive relationship between DPDOSY and fluorescence colors was constructed, allowing the visual differentiation of molecular weight. Moreover, the fluorescence color could be regulated by introducing a competitive molecule to induce the depolymerization of supramolecular polymers.

A Strategy Based on Aggregation‐Induced Ratiometric Emission to Differentiate Molecular Weight of Supramolecular Polymers

AbstractMolecular weight has an important bearing on the properties of supramolecular polymers. However, the intuitive differentiation of the molecular weight of supramolecular polymers remains challenging. Given this situation, establishing a reliable relationship between fluorescence properties and molecular weight may be a promising strategy. Herein, we prepared a supramolecular monomerM1with aggregation‐induced ratiometric emission characteristics. With the increasingM1concentration (0.100–100 mM), the average degree of polymerization (DPDOSY) rose from 1.00 to 293. Meanwhile, the color changed from dark blue to cyan, finally to yellow‐green in the same concentration range. Hence, the intuitive relationship between DPDOSYand fluorescence colors was constructed, allowing the visual differentiation of molecular weight. Moreover, the fluorescence color could be regulated by introducing a competitive molecule to induce the depolymerization of supramolecular polymers.

Effects of physical aging on the self‐healing, shape memory, and crystallization behaviors of hydrogen‐bonded supramolecular polymers

AbstractDespite the profusion of studies on synthesis, structure, and properties of supramolecular polymers (SMPs), physical aging, and its effects on properties of SMPs have been rarely described in the literature. In this study, SMPs was synthesized by end‐functionalized with 2‐ureido‐4[1H]‐pyrimidione (UPy) to triblock oligomers with soft poly(butylene) segments and hard poly (l‐lactic acid) blocks. Effects of physical aging on thermal, self‐healing properties, shape memory, as well as mechanical properties before and after repair of such SMPs have been studied. The self‐healing efficiency of SMPs increased considerably after physical aging process. After being aged at 33 °C for 120 h, light healable SMPs with a self‐healing efficiency of 100% can be achieved, as compared to the unaged SMPs of 50%. Moreover, it was found that the strength, modulus, and toughness of SMPs decreased gradually during the physical aging; on the contrary, the recovery of strength, modulus, and toughness after repair increased dramatically. The shape recovery speed and shape memory capability of SMPs can also be facilitated by extension of aging time.

Synthesis and properties of biodegradable supramolecular polymers based on polylactide-block -poly(δ -valerolactone)-block -polylactide triblock copolymers

Biodegradable supramolecular polymers (SMPs) are synthesized by the end-functionalization of poly(lactide)-block-poly(δ-valerolactone)-block-poly(lactide) (PLA-PVL-PLA) triblock copolymers with 2-ureido-4[1H]-pyrimidinone (UPy) self-complementary quadruple hydrogen-bonding unites. The end-functionalized PLA-PVL-PLA copolymers exhibit the typical characteristics of thermoplastic elastomers. Thermal, crystallization behavior, crystalline structure and properties of SMPs can be adjusted by changing the length and stereostructure of PLA blocks. The UPy groups retard the crystallization of PLA and PVL blocks, the crystallization of PVL blocks is also depressed by the increasing PLA blocks. Tensile test reveals that the prepared SMPs presents excellent mechanical properties, DMA results indicate that the heat resistance of L-SMPs is better than that of DL-SMPs. Shape memory property of SMPs was also studied, found that recovery ratio of SMPs with PDLLA blocks can reach 100%. The recovery ratio of L-SMPs was depressed as the crystallizable PLLA blocks increase. This study has systemically investigated that effect of the composition, stereostructure, and crystallizability of PLA blocks on the properties of supramolecular polymers, which would provide potential approaches to synthesize the biodegradable supramolecular polymers with tunable properties.

Orthogonal self-assembly of stimuli-responsive supramolecular polymers using one-step prepared heterotelechelic building blocks

The one-step preparation of heterodifunctional telechelic polymers containing 2,2′:6′,2′′-terpyridine (tpy) and 2-ureido-4[1H]-pyrimidinone (UPy) end-groups, as orthogonal supramolecular moieties, is reported. The utilization of an appropriately functionalized alkoxyamine, as an initiator for the nitroxide-mediated radical polymerization (NMP), directly constitutes the end-groups of the resultant polymers. The targeted alkoxyamines are based on the nitroxide structure of 2,2,5-trimethyl-3-(1-phenylethoxy)-4-phenyl-3-azahexane (TIPNO) and were obtained via stepwise functionalization of a heterodifunctional alkoxyamine skeleton. Controlled radical polymerization of styrenics using the alkoxyamine tpy–TIPNO–UPy, as an initiator, is demonstrated to generate well-defined telechelic polymers in one step. These telechelics represent promising building blocks for supramolecular architectures via self-assembly processes, yielding linear chain-extended polymers of high molar masses. Due to the orthogonality of the metal ion complexation and hydrogen bonding, the system can be addressed selectively by external stimuli. Besides for various applications, e.g. as self-healing materials, the strategy is highly attractive for tailoring the material's properties of supramolecular polymers, since the nature and the length of the polymer chain between the terminal supramolecular motifs can be controlled in a facile way.