Strategy of “Block Blends” to Generate Polymeric Thermogels versus That of One-Component Block Copolymer

Abstract

Polymer alloys are usually classified into polymer blends and block copolymers. Herein, we combine the two alloying strategies to endow materials with a thermoinduced sol–gel transition. Our system is composed of two amphiphilic block copolymers in water, and we suggest terming it a “block blend.” A series of “computer experiments” by dynamic Monte Carlo simulations were carried out to verify our idea of “block blends” and revealed the mechanism of the underlying physical gelation. A thermogel was achieved after blending two amphiphilic block copolymers with different lengths of hydrophobic and hydrophilic blocks and thus different extents of the hydrophilicity–hydrophobicity balances, in which one copolymer could otherwise always flow and the other could be insoluble in water prior to the blending. It is thus interesting that “block blends” can make non-thermogellable copolymers useful in thermogellable systems. We also examined “averaged” copolymers which shared the same composition with the block blends, and our comparative studies illustrated that the block blends impregnated richer physics. A thermogel has a percolated micelle network. Although the amphiphilicity of the copolymer determines the micelle formation, the spatial heterogeneity of two copolymers is crucial in further formation of the network, where semibald micelles are connected by hydrophobic channels rich in the relatively more hydrophobic copolymer. The block-blend strategy paves a way to generate an intelligent material, in particular, a biomaterial by hierarchical self-assembly.

Decisive Influence of Hydrophobic Side Chains of Polyesters on Thermoinduced Gelation of Triblock Copolymer Aqueous Solutions

“…To understand the temperature-triggered sol–gel transition process, the morphology evolution of PCOL–PEG–PCOL ( P3 ) triblock copolymer in water was investigated. Amphiphilic copolymers easily self-assemble into spherical micelles containing hydrophobic cores and hydrophilic shells in water . DPH, a hydrophobic dye probe, was adopted to determine the formation of polymeric micelles.…”

“…To date, various thermosensitive and biodegradable hydrogel systems have been developed based on amphiphilic block copolymers composed of poly­(ethylene glycol) (PEG) as the hydrophilic block and versatile polyesters such as poly­( d , l -lactic acid) (PLA), , poly­( d , l -lactic acid- co -glycolic acid) (PLGA), , poly­(ε-caprolactone) (PCL), , poly­(ε-caprolactone- co -glycolic acid) (PCGA), poly­(ε-caprolactone- co - d , l -lactic acid) (PCLA), and poly­(δ-valerolactone- co - d , l -lactic acid) (PVLA) as the hydrophobic block. Their temperature-induced gelation stems from subtle balance between hydrophilic/hydrophobic components. , Making use of the principle, the gel performance and degradation behavior of thermosensitive PEG/polyester copolymer hydrogels can be tailored via modulating molecular weight (MW) and MW distribution of polymers, polyester composition and sequence, block ratio, topology morphology, and even end group. , Taking ABA-type triblock copolymers as an example, in which A represents the hydrophobic block and B is the hydrophilic one, only when the MW of PEG is 1000–2000 and the block length and composition of polyester are suitable, they can form thermosensitive hydrogels . Changing the topological morphology of triblock copolymer hydrogels from ABA type to BAB type results in the increase of sol–gel transition temperature ( T gel ) and the shrinkage of gel window .…”

“…Their temperature-induced gelation stems from subtle balance between hydrophilic/hydrophobic components. 34,35 Making use of the principle, the gel performance and degradation behavior of thermosensitive PEG/polyester copolymer hydrogels can be tailored via modulating molecular weight (MW) 29 and MW distribution of polymers, 36 polyester composition and sequence, 37 block ratio, 29 topology morphology, 31 and even end group. 34,38 Taking ABA-type triblock copolymers as an example, in which A represents the hydrophobic block and B is the hydrophilic one, only when the MW of PEG is 1000−2000 and the block length and composition of polyester are suitable, they can form thermosensitive hydrogels.…”

Critical adhesion areas of cells on micro-nanopatterns

“…The cross point of two tangential lines was employed to determine the critical point. In this way, we obtained the critical area from apoptosis to survival A*, similar to the determination of critical micelle concentration (CMC) from the optical density (OD) versus amphiphile concentration in studies of the micellization transition of amphiphiles in a selective solvent [73,74]. Similarly, we defined a microisland with at least two cells as "multioccupied. "…”

Coordination Insertion Mechanism of Ring‐Opening Polymerization of Lactide Catalyzed by Stannous Octoate†

“…[ 30‐38 ] For example, PEG/polyester amphiphilic block copolymers play an important role in the thermogel family as a versatile injectable matrix in many medical fields such as tissue engineering, controlled drug release, prevention of postoperative adhesion, submucosal cushion for endoscopic submucosal dissection. [ 39‐55 ]…”