Micellization and gelation of aqueous solutions of star-shaped PEG-PCL block copolymers consisting of branched 4-arm poly(ethylene glycol) and polycaprolactone blocks

Star-shaped block copolymers consisting of non-toxic poly(ethylene glycol) and biodegradable polycaprolactone ((PEG5K-PCL)₄) were synthesized by ring-opening polymerization of the ε-caprolactone monomer with hydroxyl-terminated 4-armed PEG as initiator. These biodegradable, amphiphilic star block copolymers showed micellization and sol-gel transition behaviors in aqueous solution with varying concentration and temperature. In the dilute aqueous solutions of star block copolymers, micellization behavior occurred over specific concentration. The 1,6-diphenyl-1,3,5-hexatriene (DPH) solubilization method was used to determine the critical micellization concentration (CMC) of star block copolymers. The obtained micelle size increased with increasing hydrophobic PCL block length. In high-concentration solutions, the star block copolymers showed temperature-sensitive sol-gel transition behavior. The morphology of the micelle and gel was investigated by atomic force microscopy (AFM). As a result, the micelles showed a core-corona spherical structure at concentration near CMC, while the gel showed a mountain-chain-like morphology picture. It was proposed that with increasing the micelle concentration the worm-like micelle clusters formed firstly and the gel was constructed by the packing of micelle clusters.     

嵌段共聚物OSM1-PCLA-PEG-PCLA-OSM1的合成及其pH和温度敏感性

采用开环聚合法和自由基聚合法合成了生物可降解嵌段共聚物OSM1-PCLA-PEG-PCLA-OSM1, 并对其进行了结构表征. 采用荧光分光光度计和激光粒度仪对共聚物溶液临界胶束浓度(CMC)和粒径大小及分布进行了考察, 研究了温度和pH对共聚物胶束形成的影响. 相转变过程研究结果表明, 共聚物溶液具有pH和温度双重敏感性. 共聚物溶液在一定温度和pH条件下可发生溶液-凝胶相转变.     

Sol‐gel transition behavior of amphiphilic comb‐like poly[(PEG‐b‐PLGA)acrylate] block copolymers

The effects of comb‐like amphiphilic block copolymer architectures on the physical properties such as sol‐gel transition and micellization behaviors with the change of temperature and pH were examined. Comb‐like poly((poly(ethylene glycol)‐b‐(poly(lactic acid‐co‐glycolic acid))acrylate‐co‐acrylic acid) (poly((PEG‐b‐PLGA)A‐co‐AA)) copolymers were synthesized by coupling of poly(acrylic acid) (PAA) with two different kinds of PEG‐b‐PLGA diblock copolymers to investigate the effects of the number of branches and hydrophilicity/hydrophobicity on the sol‐gel transition and micellization. The molecular weights and chemical structures were confirmed by GPC and ¹H NMR. The number of PEG‐b‐PLGA branches was gradually deviated from the feed molar ratio with increasing the molecular weight and the number of branches and due to the bulkiness of PEG‐b‐PLGA. Poly[(PEG‐b‐PLGA)A‐co‐AA] aqueous solutions showed thermosensitive sol‐gel transition behavior, and the gelation took place at lower concentration with increasing the number of branches and PLGA chain length due to the increase of hydrophobicity. The temperature, at which abrupt increase of viscosity by dynamic rheometer appeared, was also in good agreement with sol‐gel transition by tube‐titling method. The CMC, calculated from UV‐Visible spectroscopy using DPH as hydrophobic dye, also decreased with increasing the number of PEG‐b‐PLGA branches and PLGA chain length with same reason. The micelle size was increased with increasing temperature at the initial stage, however, decreased with further increase of temperature, since the micelles were, first, aggregated by hydrophobic intermolecular interaction, and then fragmented by dehydration of PEG segments with increasing temperature. PH‐sensitive PAA backbone played a key role in physical properties. With decreasing pH, sol‐to‐gel transition temperature, CMC values, and micelle size were decreased because of the increase of hydrophobicity resulting form non‐ionized acrylic acid. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1287–1297, 2010     

Non-ionic amphiphilic block copolymers by RAFT-polymerization and their self-organization

Water-soluble, amphiphilic diblock copolymers were synthesized by reversible addition fragmentation chain transfer polymerization. They consist of poly(butyl acrylate) as hydrophobic block with a low glass transition temperature and three different nonionic water-soluble blocks, namely, the classical hydrophilic block poly(dimethylacrylamide), the strongly hydrophilic poly(acryloyloxyethyl methylsulfoxide), and the thermally sensitive poly(N-acryloylpyrrolidine). Aqueous micellar solutions of the block copolymers were prepared and characterized by static and dynamic light scattering analysis (DLS and SLS). No critical micelle concentration could be detected. The micellization was thermodynamically favored, although kinetically slow, exhibiting a marked dependence on the preparation conditions. The polymers formed micelles with a hydrodynamic diameter from 20 to 100 nm, which were stable upon dilution. The micellar size was correlated with the composition of the block copolymers and their overall molar mass. The micelles formed with the two most hydrophilic blocks were particularly stable upon temperature cycles, whereas the thermally sensitive poly(N-acryloylpyrrolidine) block showed a temperature-induced precipitation. According to combined SLS and DLS analysis, the micelles exhibited an elongated shape such as rods or worms. It should be noted that the block copolymers with the most hydrophilic poly(sulfoxide) block formed inverse micelles in certain organic solvents.     

聚丙烯酰胺/聚L-谷氨酸苄酯接枝共聚物的合成及其胶束制备

以聚丙烯酰胺(PAM)为大分子引发剂, 采用开环聚合方法, 在N,N-二甲基甲酰胺(DMF)中引发L-谷氨酸苄酯环内酸酐(BLG-NCA)聚合合成了两亲性聚丙烯酰胺/聚L-谷氨酸苄酯接枝共聚物(PAM-g-BLG), 采用IR, 1H NMR和GPC方法对共聚物结构进行了表征; 用芘作荧光探针, 研究了共聚物胶束的形成及其临界胶束浓度(cmc), 利用动态光散射(DLS)和透射电镜(TEM)研究了胶束的粒径分布和形态. 结果表明, PAM能够引发BLG-NCA开环聚合得到接枝共聚物, 在一定条件下接枝共聚物能够形成球形的稳定胶束, cmc值和胶束粒径随着共聚物中疏水性聚L-谷氨酸苄酯(PBLG)链段含量的增加而减小.     

Thermosensitive sol–gel transition behaviors of poly(ethylene oxide)/aliphatic polyester/poly(ethylene oxide) aqueous solutions

The thermoreversible gelation of Pluronic [poly(ethylene oxide) (PEO)–polypropylene oxide (PPO)–PEO] aqueous solutions originates from micelle formation and micelle volume changes due to PEO–water and PPO–water lower critical solution temperature behavior. The micelle volume fraction is known to dominate the sol–gel transition behavior of Pluronic aqueous solutions. Triblock copolymers of PEO and aliphatic polyesters, instead of PPO, were prepared by hexamethylene diisocyanate coupling and dicyclohexyl carbodiimide coupling. Through changes in the molecular weight and hydrophobicity of the polyester middle block, the hydrophobic–hydrophilic balance of each block was systematically controlled. The following aliphatic polyesters were used: poly(hexamethylene adipate) (PHA), poly(ethylene adipate) (PEA), and poly(ethylene succinate) (PESc). With the hydrophobicity and molecular weight of the middle block increasing, the critical micelle concentration at the same critical micelle temperature decreased, and the absolute value of the micellization free energy increased. The micelle size was rather insensitive to temperature but slightly decreased with increasing temperature. PEO–PHA–PEO and PEO–PEA–PEO triblock copolymers needed high polymer concentrations to form gels. This was ascribed to the tight aggregation of PHA and PEA chains in the micelle core due to strong hydrophobic interactions, which induced the contraction of the micelle core. However, because of the relatively hydrophilic core, a PEO–PESc–PEO aqueous solution showed gelation at a low polymer concentration. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 772–784, 2004     

两亲性嵌段共聚物PS-b-PMAA的合成与胶束化行为研究

利用原子转移自由基聚合法(ATRP)得到了分子量可控、分子量分布接近1.1的聚苯乙烯-b-聚甲基丙烯酸叔丁酯(PS-b-PtBMA)嵌段共聚物, 进而在酸性条件下由水解反应得到了两亲性的聚苯乙烯-b-聚甲基丙烯酸 (PS-b-PMAA)嵌段共聚物．用GPC, FTIR和¹H-NMR等对产物的分子量和组成进行了表征．使PS-b-PMAA在选择性溶剂中进行自组装, 通过激光光散射和透射电子显微镜研究了影响其胶束化行为的因素与胶束形态, 并初步探讨了胶束形成的机理, 发现通过控制嵌段共聚物的链段长度之比可得到空心球形的高分子胶束．     

Synthesis and self-assembly behavior of thermoresponsive triblock copolymer

Block copolymers comprising thermosensitive poly(N-isopropylacrylamide) (PNIPAM) and hydrophobic poly(n-butyl acrylate) (PBA) blocks, were synthesized using the reversible addition-fragmentation chain transfer polymerization (RAFT), their thermosensitive behavior was studied by ultraviolet spectrophotometer (UV) and dynamic light scattering (DLS). The lower critical solution temperature (LCST) was strongly correlated to the hydrophobic/hydrophilic ratio of the copolymers. Their micellization and self-assembly behavior in dilute aqueous solution were studied by surface tension (SFT), DLS and TEM. The resulting block copolymers reversibly formed or deformed micellar assemblies during their LCSTs. The critical micelle concentration (CMC) was controlled by the composition of PBA and PNIPAM, indicating the successful formation of the block copolymers.     

New biodegradable amphiphilic block copolymers of epsilon-caprolactone and delta-valerolactone catalyzed by novel aluminum metal complexes. II. Micellization and solution to gel transition

In our previous study [J. Yang, L. Jia, L. Yin, J. Yu, Z. Shi, Q. Fang, A. Cao, Macromol. Biosci. 2004, 4, 1092.], new biodegradable copolymers of diblock methoxy poly(ethylene glycol)-block-poly(epsilon-caprolactone) and methoxy poly(ethylene glycol)-block-poly(delta-valerolactone), and triblock poly(epsilon-caprolactone)-block-poly(ethylene glycol)-block-poly(epsilon-caprolactone) and poly(delta-valerolactone)-block-poly(ethylene glycol)-block-poly(delta-valero-lactone) bearing narrow molecular weight distributions and well-defined block architectures were reported to be prepared with our original aluminum metal complex templates. This work will continue to report new investigations on their water solubility, and reversible thermal responsive micellization and solution to gel transition in distilled water. Among the new synthesized copolymers (P1-P23), seven diblock or triblock samples (P3, P6, P7, P11, P12, P19, and P21) with higher hydrophilic building block populations were revealed to be water soluble under ambient temperature. By means of UV spectrophotometer attached with a thermostat, important parameters as critical micellization mass concentrations (CMCs) and critical micellization temperatures (CMTs) were characterized for these new amphiphile dilute aqueous solution with the aid of an lipophilic organic dye probe of 1,6-diphenyl-1,3,5-hexatriene (DPH). Furthermore, the critical gelation temperatures (CGTs) were simultaneously investigated for these water-soluble block copolymers via a tube tilting method. It was found that the CMC, CMT, and CGT were strongly affected by the population and nature of the hydrophobic building blocks, and a higher hydrophobicity of the new amphiphilic block copolymer finally led to lower CMC and CMT, and higher CGT. In addition, the salts of KBr and NaCl were found to play as a salt-out effect on the solution to gel transition for the diblock P6 and triblock P11, exhibiting an interesting tunable gelation temperature close to 35-42 degrees C. These results will pave new possibility for the synthesized block structural amphiphiles as potential biomaterials to be applied in vivo.     

Biodegradable and stimuli sensitive amphiphilic graft copolymers and their sol–gel phase transition behavior

pH and temperature‐sensitive biodegradable poly(β‐aminoester)‐graft‐poly(ε‐caprolactone)‐block‐methoxy poly(ethylene glycol) (PBAE‐g‐PCL‐b‐mPEG) amphiphilic graft copolymers with different molecular weights were synthesized. The structure of these copolymers was adjusted by varying the feed ratios of ε‐caprolactone to methoxy poly(ethylene glycol)s (mPEG), amine and diacrylate monomer amounts and the molecular weight of mPEG. Aqueous solutions of these copolymers formed micelles at lower concentrations; however, the concentrated solutions showed a reversible sol–gel transition property depending on both pH and temperature changes under representative physiological conditions (pH 7.4, 37°C). The effects of the molecular weight of pH‐sensitive poly(β‐aminoester) block and mPEG group, the hydrophobic to hydrophilic block ratio (PCL/mPEG) and the concentration of the copolymer on the sol–gel transition were investigated. Proton nuclear magnetic resonance (¹H NMR) and gel permeation chromatography measurements were used to characterize the structure of the synthesized copolymers. The self‐assemble behavior and critical micelle concentration of the amphiphilic copolymers were estimated in phosphate buffer solution using fluorescence spectroscopy. The gelling behavior was measured by using tube inversion method. At pH 7.4, all copolymer solutions prepared 20 wt% concentration indicated sol–gel transition with increasing temperature. In vitro degradation experiments displayed that the synthesized graft copolymers mostly degraded hydrolytically within 20 days under physiological conditions. In order to investigate the potential application of synthesized hydrogels in drug delivery, Methylene Blue was used and approximately 70% of the loaded amount was released in 120 hr. The findings indicate that obtained graft copolymers can be used as injectable biodegradable carriers for pharmaceutical drugs. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis and Self-Assembly Behaviors of Four-Arm Star Block Copolymers Poly(ϵ-caprolactone)-b-poly(2- (diethylamino) ethyl methacrylate)) in Aqueous Solution

Four-arm star block polymers consisting of hydrophobic poly(?-caprolactone) (PCL) block and hydrophilic poly(2-(diethylamino) ethyl methacrylate)) (PDEAEMA) block were successfully synthesized by ring opening polymerization (ROP) and atom transfer radical polymerization (ATRP). Chain lengths of PDEAEMA segments were varied to obtain a series of star copolymers with different hydrophilic/hydrophobic ratio, which were desired for self-assembly study. Dynamic light scattering (DLS) and transmission electron microscopic (TEM) were used to study their self-assembly behavior. In the PBS solution with different pH value, the star polymers formed micelles or nanoparticles. Furthermore, the morphologies of the micelles were also pH-dependent. Critical micelle concentrations of star copolymers changed from 5.0 to 17.5 mg/L with the increase of hydrophilic block length or the pH decrease. Moreover, a steady increase was found on the micelles diameters when the pH decreased from 7.0 to 3.0. The low CMC value and slight changes on micelle diameter indicated that the micelle remained stable under the changing external stimulus.     

Phase‐transition characteristics of amphiphilic poly(2‐ethyl‐2‐oxazoline)/poly(ε‐caprolactone) block copolymers in aqueous solutions

Amphiphilic diblock and triblock copolymers of various block compositions based on hydrophilic poly(2‐ethyl‐2‐oxazoline) (PEtOz) and hydrophobic poly(ε‐caprolactone) were synthesized. The micelle formation of these block copolymers in aqueous media was confirmed by a fluorescence technique and dynamic light scattering. The critical micelle concentrations ranged from 35.5 to 4.6 mg/L for diblock copolymers and 4.7 to 9.0 mg/L for triblock copolymers, depending on the block composition. The phase‐transition behaviors of the block copolymers in concentrated aqueous solutions were investigated. When the temperature was increased, aqueous solutions of diblock and triblock copolymers exhibited gel–sol transition and precipitation, both of which were thermally reversible. The gel–sol transition‐ and precipitation temperatures were manipulated by adjustment of the block composition. As the hydrophobic portion of block copolymers became higher, a larger gel region was generated. In the presence of sodium chloride, the phase transitions were shifted to a lower temperature level. Sodium thiocyanate displaced the gel region and precipitation temperatures to a higher temperature level. The low molecular weight saccharides, such as glucose and maltose, contributed to the shift of phase‐transition temperatures to a lower temperature level, where glucose was more effective than maltose in lowering the gel–sol transition temperatures. The malonic acid that formed hydrogen bonds with the PEtOz shell of micelles was effective in lowering phase‐transition temperatures to 1.0M, above which concentration the block copolymer solutions formed complex precipitates. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2400–2408, 2000     

聚L-丙氨酸-聚乙二醇嵌段共聚物的胶束化行为研究

以氨基聚乙二醇单甲醚(MPEG-NH₂)为大分子引发剂, 采用开环聚合方法合成了聚L-丙氨酸-聚乙二醇嵌段共聚物(PAME), 并对其结构进行了表征; 用圆二色谱(CD)研究了嵌段共聚物在水溶液中的二级结构, 用芘荧光探针技术研究了共聚物胶束的形成及其临界胶束浓度(CMC), 利用动态光散射(DLS)和透射电镜(TEM)研究了胶束的粒径分布和形态. 结果表明, 在水溶液中共聚物链以α-螺旋构象形式存在, 在一定条件下嵌段共聚物能够形成球形的稳定胶束, PAME-1形成胶束的CMC为1.99×10^-5 mol/L, CMC值受共聚物中聚L-丙氨酸(PLA)链段含量的影响.     

Synthesis and Characterization of Surfactant PEG Macromonomers with Fluorocarbon End‐capped Groups and its Copolymers

Fluorocarbon (R_F) or hydrocarbon (R_H) end‐capped PEG macromonomers were prepared by coupling method. Several factors mat affect the synthesis were studied and optimum condition was obtained. The critical micelle concentrations (CMC) of these macromonomers were determined by fluorescence method. A new type of fluorocarbon‐containing hydrophobically modified alkali swellable/soluble copolymers were obtained by copolymerization of R_F or R_H alkyl endcapped PEG macromonomers with acrylic acid in organic solvent The preliminary researches on viscosity property of these copolymer solutions were conducted under different conditions, such as various macromonomer content in the copolymer, polymer concentration, shear rate, pH value and temperature. All the results proved that there existed a very strong hydrophobic association among hydrophobes in these copolymer solutions.     

The research on multi‐responsive azobenzene block copolymer and its self‐assembly behavior

The azobenzene‐based amphiphilic copolymers have drawn significant attention as a kind of multi‐responsive smart materials. The demand on deeper investigation of how the azobenzene group influences the micelles formation and light‐responsive behavior on molecular level is very urgent. In this article, multi‐responsive block copolymers, poly (acrylic acid)‐block‐poly[4'‐[[(2‐Methacryloyloxy)ethyl]ethylainino]azobenzene‐co‐poly (ethylene glycol) methyl ether methacrylate] (PAA‐b‐P (AzoMA‐co‐PEGMA)), with pH‐, light‐ and reduction‐responsiveness were synthesized by the monomers of AzoMA, PEGMA and acrylic acid via reversible addition‐fragmentation chain transfer polymerization (RAFT). The amphiphilic block copolymer presented aggregation‐induced emission effect, and it was pH, light, and reduction responsive. The results showed that the micelle size decreased with the decreasing of pH within a certain range. However, the particle size of micelles increased significantly when the pH was 4. Once adding reduction agent, the micelles were disassembly. Fluorescent molecule of Nile red was selected as a hydrophobic guest molecule to study the properties of encapsulating and releasing abilities of block copolymer micelles for guest molecules. The results showed that the loading capacity of three kinds of copolymer micelles was closely related to the aggregates formed by the hydrophobic block, mainly azobenzene block. Besides, the block copolymer micelles could release a certain amount of Nile red under the irradiation of UV light, the reduction with Na₂S₂O₄ as reductant, and the exposure to alkaline environment. The mechanism of how the different status of azobenzene group influenced the self‐assembly and multi‐responsive behavior was explored on molecular level.     

Chaotropic‐Anion‐Induced Supramolecular Self‐Assembly of Ionic Polymeric Micelles

Traditional micelle self‐assembly is driven by the association of hydrophobic segments of amphiphilic molecules forming distinctive core–shell nanostructures in water. Here we report a surprising chaotropic‐anion‐induced micellization of cationic ammonium‐containing block copolymers. The resulting micelle nanoparticle consists of a large number of ion pairs (≈60 000) in each hydrophobic core. Unlike chaotropic anions (e.g. ClO₄^?), kosmotropic anions (e.g. SO₄^2?) were not able to induce micelle formation. A positive cooperativity was observed during micellization, for which only a three‐fold increase in ClO₄^? concentration was necessary for micelle formation, similar to our previously reported ultra‐pH‐responsive behavior. This unique ion‐pair‐containing micelle provides a useful model system to study the complex interplay of noncovalent interactions (e.g. electrostatic, van der Waals, and hydrophobic forces) during micelle self‐assembly.     

聚(L-丙氨酸-co-羟丙-L-谷氨酰胺)无规共聚物的两亲性及其胶束行为研究

采用丙氨酸作为疏水聚合单体,谷氨酸作为亲水聚合单体,一步开环聚合反应,合成了具有两亲性的聚氨基酸无规共聚物.利用IR,1H-NMR等方法对所合成的聚合物进行了详细的表征,结果表明两种单体都能够按照投料比参加聚合反应生成无规共聚物.对比聚丙氨酸-聚羟丙谷氨酰胺嵌段共聚物,探讨了无规共聚物与嵌段共聚物在两亲性及结构性质上的差异和特点.研究表明,聚(L-丙氨酸-co-羟丙-L-谷氨酰胺)无规共聚物与嵌段共聚物一样,具有两亲性,在水溶液中也能够形成胶束,但胶束尺寸较嵌段共聚物要小,胶束形态也不像嵌段共聚物是规整的球形.实验发现,亲疏水单体的比例对胶束的形成有很大影响,P(A10-co-HPG40)所制得的胶束分散最为均匀.所形成的胶束以疏水的聚丙氨酸为内核,亲水的聚羟丙谷氨酰胺为外壳.     

Conductive properties of TiO2/bacterial cellulose hybrid fibres

In this article, we report the first micellization study of amphiphilic copolymers composed of bacterial medium chain length poly(3-hydroxyalkanoates) (mcl-PHAs). A series of diblock copolymers based on fixed poly(ethylene glycol) (PEG) block (5000 g mol(-1)) and a varying poly(3-hydroxyoctanoate-co-3-hydroxyhexanoate) (PHOHHx) segment (1500-7700 g mol(-1)) have been synthesized using "click" chemistry. These copolymers self-assembled to form micelles in aqueous media. The influence of PHOHHx block molar mass on the hydrodynamic size and on the critical micelle concentration (CMC) has been studied using dynamic light scattering and fluorescence spectroscopy, respectively. With increasing PHOHHx length, narrowly distributed micelles with diameters ranging from 44 to 90 nm were obtained, with extremely low CMC (up to 0.85 mg/L). Cryogenic transmission electron microscopy (Cryo-TEM) showed that micelles took on a spherical shape and exhibited narrow polydispersity. Finally, the colloidal stability of the micelles against physiological NaCl concentration has been demonstrated, suggesting they are promising candidates for drug delivery applications.     

Micellization and Thermogelation of Poly(ether urethane)s Comprising Poly(ethylene glycol) and Poly(propylene glycol)

A series of multiblock poly(ether urethane)s comprising poly(ethylene glycol) (PEG), and poly(propylene glycol) (PPG) segments were synthesized. Their aqueous solutions exhibited thermogelling behavior at critical gelation concentrations (CGC) ranging from 8 to 12 wt%. The composition and structural information of the copolymers were studied by GPC and ¹H NMR. The critical micellization concentration (CMC) and thermodynamic parameters for micelle formation were determined at different temperatures. The temperature response of the copolymer solutions were studied and found to be associated with the composition of the copolymers.     

Synthesis and Self-Association of Stimuli-Responsive Diblock Copolymers by Living Cationic Polymerization

The living cationic polymerization of several functional monomers in the presence of an added base is investigated as a possible preparation of a new series of water-soluble or stimuli-responsive copolymers. Under appropriate conditions, the polymerization allows the selective preparation of polymers with various shapes and different sequence distributions of monomer units, including stimuli-responsive block copolymers, gradient copolymers, poly(vinyl alcohol) graft copolymers, and star-shaped polymers. The stimuli-induced self-association of the diblock copolymers is also examined. An aqueous solution of the diblock copolymer with a thermo-sensitive segment undergoes rapid physical gelation upon warming to the critical temperature to give a transparent gel, and returns sensitively to the solution state upon cooling. The sharp transition of stimuli-responsive segments with highly controlled primary structure turns out to play an important role in the self-association. Small-angle neutron scattering, dynamic light scattering, and electron microscopy studies reveal that the physical gelation involves a thermosensitive micellization of diblock copolymers (core size: 18-20 nm) and subsequent micelle macrolattice formation (bcc symmetry). Based on the gelation mechanism, several stimuli-responsive gelation systems are achieved using other stimuli such as the addition of a selective solvent or compound, cooling, pH change, and irradiation with ultraviolet light.