Preparation of light-stable micelles with azo dyes from a nonamphiphilic random block copolymer

Light-stable micelles with azo dyes were prepared by micelle formation of a nonamphiphilic diblock copolymer containing azobenzene and UV absorbent at ca. 1 mol% as the unit ratios. The nonamphiphilic block copolymer consists of two different kinds of random copolymer blocks: poly[4-(phenylazophenoxymethyl)styrene-co-vinylphenol] (P(AS-co-VPh)) and poly[4-(2-hydroxybenzophenoxymethyl)styrene-co-styrene] (P(HBS-co-St)). This random block copolymer, P(AS-co-VPh)-b-P(HBS-co-St) formed the micelles in the presence of 1,4-butanediamine (BDA) through hydrogen bond cross-linking between the VPh units via BDA. The micelles had the azobenzene moieties at the cores and the UV absorbents at the coronas. The micelles showed a small color difference in color fading experiments, in comparison with the unimers and with micelles having no UV absorbent at the coronas. It is significant that the diblock copolymer forms the micelles and has the UV absorbents at the coronas to suppress the color fading. Furthermore, the chain length of ,-diamines had no effect on the hydrodynamic radius of the micelles, but affected the aggregation number and the cmc.     

Synthesis and micelle formation of triblock copolymers of poly(methyl methacrylate)-b-poly(ethylene oxide)-b-poly(methyl methacrylate) in aqueous solution

Amphiphilic triblock copolymers of poly(methyl methacrylate)-b-poly(ethylene oxide)-b-poly(methyl methacrylate) (PMMA-b-PEO-b-PMMA) with well-defined structure were synthesized via atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) initiated by the PEO macroinitiator. The macroinitiator and triblock copolymer with different PMMA and/or PEO block lengths were characterized with ¹H and ¹³C NMR and gel permeation chromatography (GPC). The micelle formed by these triblock copolymers in aqueous solutions was detected by fluorescence excitation and emission spectra of pyrene probe. The critical micelle concentration (CMC) ranged from 0.0019 to 0.016 mg/mL and increased with increasing PMMA block length, while the PEO block length had less effect on the CMC. The partition constant K_v for pyrene in the micelle and in aqueous solution was about 10⁵. The triblock copolymer appeared to form the micelles with hydrophobic PMMA core and hydrophilic PEO loop chain corona. The hydrodynamic radius R_h,app of the micelle measured with dynamic light scattering (DLS) ranged from 17.3 to 24.0 nm and increased with increasing PEO block length to form thicker corona. The spherical shape of the micelle of the triblock copolymers was observed with an atomic force microscope (AFM). Increasing hydrophobic PMMA block length effectively promoted the micelle formation in aqueous solutions, but the micelles were stable even only with short PMMA blocks.     

Low temperature ATRP of POSS-MA and its amphiphilic pentablock copolymers

A low temperature ATRP of methacryloisobutyl POSS (POSS-MA) is carried out, using poly(propylene glycol) (PPG)-based macroinitiator, in toluene with CuCl/PMDETA as the catalyst system, generating well-defined P(POSS-MA)-b-PPG-b-P(POSS-MA) triblock copolymer with Р~ 1.1. The semilogarithmic kinetic plot reveals first-order kinetics and the dispersity is observed to decrease as the reaction progresses—an indication of the controlled behavior of the polymerization. To assess the chain-end fidelity of the produced block copolymer, chain extension is carried out with oligo(ethylene glycol methacrylate) (OEGMA) that afforded water-soluble P(OEGMA)-b-P(POSSMA)-b-PPG-b-P(POSSMA)-b-P(OEGMA) pentablock copolymers. The SEC profiles suggest a quantitative initiation by the macroinitiator. By varying the monomer to initiator molar ratio, block copolymers with various P(OEGMA) chain lengths, ranging from 19 to 58 units on each side have been achieved with relative lower dispersity (Р< 1.4). Kinetic analysis of the ATRP of OEGMA, with P(POSSMA)-b-PPG-b-P(POSSMA) as the macroinitiator, suggests first-order kinetics and controlled nature of the polymerization. The PPG and P(OEGMA) segments impart a thermosensitive character to the obtained water-soluble amphiphilic hybrid block copolymers; hence they display temperature-dependent self-assembly behavior in aqueous medium.     

Preparation of micelles with azo dye and UV absorbent at their cores or coronas using non-amphiphilic block copolymers

Micelles with azo dye and UV absorbent at their cores or coronas were prepared from non-amphiphilic random diblock copolymers by α,ω-diamine. Poly[4-(phenylazophenoxymethyl)styrene-ran-4-(2-hydroxybenzophenoxymethyl)styrene-ran-vinylphenol]-block-polystyrene (P(AS-r-HBS-r-VPh)-b-PSt) and poly(vinylphenol)-block-poly[4-(phenylazophenoxymethyl)styrene-ran-4-(2-hydroxybenzophenoxymethyl)styrene-ran-styrene] (PVPh-b-P(AS-r-HBS-r-St)) diblock copolymers were prepared by living radical polymerization mediated by 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl. The former copolymer had a molecular weight of Mn[P(AS-r-HBS-r-VPh)-b-PSt] = 10,000-b-250,000 by ¹H NMR and a molar ratio of AS:HBS:VPh = 0.01:0.01:0.98, while the latter had a molecular weight of Mn[PVPh-b-P(AS-r-HBS-r-St)] = 10,000-b-111,000 and a molar ratio of AS:HBS:St = 0.02:0.03:0.95. The copolymers showed no self-assembly in 1,4-dioxane because this solvent was non-selective to the copolymers. Dynamic light scattering demonstrated that the copolymers formed micelles in the solvent in the presence of α,ω-diamine. The hydrodynamic radii of the micelles slightly increased with the copolymer concentration decrease, while the aggregation numbers were almost independent of the copolymer concentration. It was found that P(AS-r-HBS-r-VPh)-b-PSt formed smaller micelles with a lower aggregation number than PVPh-b-P(AS-r-HBS-r-St) because of the steric hindrance of the AS and HBS units present at the micellar coronas.     

RAFT polymerization of linear ABC triblock copolymer P<Emphasis Type="Italic">t</Emphasis>BA-<Emphasis Type="Italic">b</Emphasis>-PS-<Emphasis Type="Italic">b</Emphasis>-P2VP and regulation of its hierarchical self-assembly structure in solution

Linear ABC triblock copolymer PtBA₁₅₄-b-PS₃₀₀-b-P2VP₂₄₀ was successfully synthesized by RAFT polymerization. Block copolymer micelles were prepared by the two-step hierarchical self-assembly process. Size exclusion chromatography and ¹H NMR were used to characterize the structure of samples. Morphologies and size of micelles were determined by transmission electron microscope. The results showed that the densely dispersed spherical micelles of PtBA₁₅₄-b-PS₃₀₀-b-P2VP₂₄₀ were obtained in the first step of the hierarchical self-assembly process. In the second step, core-compartmentalized micelle strings with different lengths and distribution densities were obtained when the primary self-assembled solution was dialyzed in distilled water with pH ≈ 3. When distilled water with pH ≈ 3 was added drop-wise to this solution, uniformly dispersed spherical core-compartmentalized micelles of PtBA₁₅₄-b-PS₃₀₀-b-P2VP₂₄₀ were prepared. Thus, hierarchical self-assembly structure of linear ABC triblock copolymer was obtained successfully and the preparation of uniformly dispersed spherical micelles of triblock copolymers was realized simply by changing the secondary self-assembly methods.     

Hybrid micelle formation from poly(ethylene oxide-b-sodium 2-acrylamido-1-propanesulfonate-b-styrene) and Fe3+ ion in aqueous solution

Organic–inorganic nanohybrid particles are prepared in aqueous solution from poly(ethylene oxide-b-sodium 2-acrylamido-1-propanesulfonate-b-styrene) (PEO-b-PAMPS-b-PS) triblock copolymer and ferric ions. The hybrid micelles were characterized by dynamic light scattering, scanning electron microscopy, transmission electron microscopy, and zeta-potential measurements. The hydrodynamic diameter of the hybrid micelles ranges from 68 to 118 nm depending on the concentration of the polymer and the amount of ferric ions loaded on the polymer. Zeta-potential measurements revealed that the micelles are assembled mainly by electrostatic interaction between the ferric ions and the negatively charged PAMPS block in the PEO-b-PAMPS-b-PS.     

Synthesis and pH-sensitive micellization of doubly hydrophilic poly(acrylic acid)-b-poly(ethylene oxide)-b-poly(acrylic acid) triblock copolymer in aqueous solutions

A doubly hydrophilic triblock copolymer poly(acrylic acid)-b-poly(ethylene glycol)-b-poly(acrylic acid) (PAA-b-PEO-b-PAA) with M _w/M _n = 1.15 was synthesized by atom transfer radical polymerization of t-butyl acrylate (tBA), followed by acidolysis of the PtBA blocks. The pH-sensitive micellization of PAA-b-PEO-b-PAA in acidic solution was investigated by potentiometric titration, fluorescence spectrum, dynamic light scattering and zeta potential. The pK _a was 6.6 and 6.0 in deionized water and in 0.1 mol/L NaCl solution, respectively. The copolymer formed micelles composed of a weakly hydrophobic core of complexed PAA and PEO and a hydrophilic PEO shell in 1 mg/mL solution at pH < 5.5 due to hydrogen bonding. The critical micelle concentration was 0.168 mg/mL at pH 2.0. At pH < 4.5, steady and narrow distributed micelles were formed. Increasing pH to 5.0, unsteady and broad distributed micelles were observed. At pH > 5.5, the micelle was destroyed owing to the ionization of the PAA blocks.     

Microphase separation in thin films of supramolecular assemblies composed of a triblock copolymer and low-molecular-weight additive

The phase behavior of supramolecular assemblies (SMAs) formed by poly(4-vinylpyridine)-block-polystyrene-block-poly(4-vinylpyridine) (P4VP-b-PS-b-P4VP) triblock copolymer with 2-(4′-hydroxybenzeneazo)benzoic acid (HABA) was investigated with respect to the molar ratio (X) between HABA and 4VP monomer unit in bulk as well as in thin films. The results were compared with SMAs formed by a PS-b-P4VP diblock copolymer of similar composition as the triblock but half the molecular weight to ascertain the effect of molecular architecture on microphase separation. In bulk, both the di- and triblock SMAs showed composition-dependent morphological transitions, which could be tuned by HABA/4VP molar ratio. The domain spacing of the SMA was not significantly affected by the molecular architecture of the constituting block copolymers. In thin films also, both the di- and triblock SMAs showed more or less similar morphological transitions depending on X. Interestingly, the domain orientation of the cylindrical or lamellar microdomains in the SMAs was influenced by the molecular architecture of the block copolymer. After chloroform annealing, although the diblock SMAs showed in-plane orientation of the domains, triblock SMAs showed perpendicular domain orientation. The perpendicular orientation of the microdomains in triblock was favored because it allowed the mid-PS blocks to acquire normal distribution of loop and bridged conformations. Furthermore, the orientation of the lamellar and cylindrical microdomains of the diblock SMAs was found to switch to perpendicular orientation after annealing in 1,4-dioxane vapors. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1594–1605, 2010     

Synthesis and characterization of Fe(II)-coordinated PS-b-P[NIPAM-co-(VBC-Fe-DMAP)] block copolymers

In this work,a new type of block polymers,polystyrene-b-poly[(N-isopropyl acrylamide)-co-(vinyl benzyl chloride)](PS-b-P(NIPAM-co-VBC)),was prepared via reversible addition fragmentation transfer polymerization,then pentacyano(4-(dimethylamino pyridine))ferrate(Fe-DMAP) was attached to VBC units through a quaternization process.The Fe(Ⅱ)-coordinated PS-b-P[NIPAM-co-(VBC-Fe-DMAP)]block copolymers were characterized by ~1H-NMR,FT-IR and TGA.The self-assembly behavior of the block copolymers was also investigated and the micelle morphology was characterized by TEM.It was found that the PS-b-P(NIPAM-co-VBC) block polymer and Fe-coordinated block copolymer could both form spherical micelles in DMF/MeOH mixed solvent.     

三嵌段共聚物PAN-b-PEG-b-PAN的合成及其自组装行为的研究

利用原子转移自由基聚合(ATRP)制得了分子量可控、分子量分布窄的聚丙烯腈-b-聚乙二醇-b-聚丙烯腈P(AN-b-PEG-b-PAN)嵌段共聚物. 通过¹H NMR, FTIR, 凝胶渗透色谱(GPC)对所得产物的结构和分子量进行了表征并通过TG和DTA考察了该嵌段共聚物的热稳定性; 运用透射电子显微镜(TEM)、荧光探针技术和动态光散射(DLS)研究了P(AN)₂₇-b-P(EG)₄₅-b-P(AN)₂₇在溶剂水中胶束的形成、结构、形貌和胶束粒径. 结果表明, 三嵌段共聚物P(AN)₂₇-b-P(EG)₄₅-b-P(AN)₂₇的热稳定性较纯聚乙二醇P(EG)好, 且柔性链PEG的引入对嵌段共聚物的放热峰位置没有显著的影响. 当改变此嵌段共聚物溶液浓度时, 该嵌段共聚物会自组装成不同形状的胶束, DLS测量的胶束粒径大于TEM观察的结果, 其临界胶束浓度(cmc)约为4.46×10^－4 g•L^－1.     

Preparation of intermediary layer crosslinked micelles from a photocrosslinkable amphiphilic ABC triblock copolymer

To prepare intermediary layer crosslinked micelles, a photocrosslinkable amphiphilic ABC triblock copolymer, poly(ethylene glycol)-b-poly(2-cinnamoyloxyethyl methacrylate)-b-poly(methyl methacrylate) (PEG-PCEMA-PMMA), was synthesized and its micellar characteristics were investigated. The triblock copolymer of PEG-b-poly(2-hydroxyethyl methacrylate)-b-PMMA (PEG-PHEMA-PMMA) (M_n = 9800 g/mol, M_w/M_n = 1.33) was first polymerized by activators generated by electron transfer (AGET) atom transfer radical polymerization (ATRP) using a PEG macroinitiator in a mixed solvent of anisole/2-isopropanol (3/1 v/v). The middle block of the copolymer was then functionalized with cinnamoyl chloride. The degrees of polymerization of the PEG, PHEMA, and PMMA blocks were 113, 18 and 21, respectively. The critical micelle concentration (CMC) of the PEG-PCEMA-PMMA was 0.011 mg/mL. The PEG-PCEMA-PMMA micelles were spherically shaped with an average diameter of 43 nm. The intermediary layer of the PEG-PCEMA-PMMA micelles was crosslinked by UV irradiation. Not all of the cinnamate groups underwent photocrosslinking probably due to a lack of other cinnamate groups in their immediate vicinity. However, the degree of photocrosslinking of the intermediary layer of the PEG-PCEMA-PMMA micelles was sufficient to give excellent colloidal stability, even in different external environments.     

Stimuli-responsive behavior of complex micelles based on double hydrophilic block copolymer and fluorescent indicator

The double hydrophilic block copolymer poly(ethylene glycol mono-methyl ether)-block-poly(4-vinylpyridine) (mPEG₄₃-b-P4VP₁₁₅) was synthesized by atom transfer radical polymerization. The structure, molecular weight and molecular weight distribution of mPEG₄₃-b-P4VP₁₁₅ were characterized by ¹H-NMR and gel permeation chromatography combined with laser light scattering technique. The complex micelles based on mPEG₄₃-b-P4VP₁₁₅ and the disodium 2-naphthol-3,6-disulfonate were obtained in acid aqueous solution. The morphologies of the complex micelles were observed by transmission electron microscopy. The revertible temperature and pH-responsive behaviors of complex micelles were studied by dynamic light scattering and fluorescence techniques.     

Thermal and self-nucleation behavior of molecular complexes formed by p-nitrophenol and the poly(ethylene oxide) end block within an ABC triblock copolymer

We have been able to prepare a molecular complex between the poly(ethylene oxide) block of a poly(ethylene)-b-poly(ethylene-alt-propylene)-b-poly(ethylene oxide) triblock copolymer and p-nitrophenol (PNP). The composition of the copolymer employed was: 24% PE, 57% PEP and 19% PEO in weight percent. The pure copolymer exhibited a non-conventional thermal behavior since the PEO block displayed a fractionated crystallization process during cooling. The PEO block/PNP complex did not show any apparent crystallization during cooling, instead cold crystallization during heating was observed and an approximately 30°C increase in melting point as compared to the neat PEO block within the copolymer. This caused an overlap in the melting regions of the PE block and the PEO block/PNP complex. The self-nucleation of the PE-b-PEP-b-PEO/PNP complex is very different from that of the neat triblock copolymer. An increased capacity for self-nucleation of the PEO block was produced by the complexation with PNP and therefore the three self-nucleation domains were clearly encountered for both the PE block and for the PEO block/PNP complex. Self-nucleation was able to show that the two crystallizable blocks can be self-nucleated and annealed in an independent way, thereby ascertaining the presence of separate crystalline regions in the triblock copolymer. Through the use of PNP, both the crystallinity and the melting point of the PE-b-PEP-b-PEO block copolymer employed here can be substantially increased. Similar results were obtained by complexation of the same ABC triblock copolymer with resorcinol.     

Self-assembly control of a pyridine-containing diblock copolymer by perfluorinated counter anions during salt-induced micellization

The micelle formation of poly[(4-pyridinemethoxymethyl)styrene]-block-polystyrene (PPySt-b-PSt) was studied in the nonselective solvent using perfluoroalkyl carboxylic acids. PPySt-b-PSt showed no self-assembly into micelles in THF, because this solvent was nonselective for the copolymer. Dynamic light scattering demonstrated that the diblock copolymer formed the micelles in the solvent in the presence of perfluoroalkyl carboxylic acids in which the number of carbons in the perfluoroalkyl chains was over eight. ¹H NMR revealed that the micellization proceeded through the salt formation of the pyridinium perfluoroalkyl carboxylate and through the aggregation of the perfluoroalkyl chains in the counter anions. The hydrodynamic radius and the aggregation number of the micelles increased with an increase in the length of the perfluoroalkyl chain. The copolymer needed less carboxylic acid with longer perfluoroalkyl chain to form the micelles. The copolymer produced the micelles with lower aggregation number and higher critical micelle concentration at higher temperature, although the micellar size was almost independent of the temperature. The micelles were unstable with respect to the variation in the temperature, and were dissociated into the unimers with the increase in the temperature. The micelles, however, were reconstructed by decreasing the temperature. This dissociation–reconstruction of the micelles was controlled reversibly not only by the temperature but also by the concentration of the perfluoroalkyl carboxylic acid. An increase in the acid concentration suppressed the dissociation into the unimers, while promoting the reconstruction of the micelles.     

Synthesis of anionic amphiphilic carbosilane block copolymer: Poly(1,1‐diethylsilacyclobutane‐block‐methacrylic acid)

An amphiphilic block copolymer of silacyclobutane and methacrylic acid (MAA) was synthesized via a living anionic polymerization of 1,1‐diethylsilacylcobutane (EtSB). Sequential addition of 1,1‐diphenylethylene and t‐butyl methacrylate (tBMA) to living poly(EtSB) in the presence of lithium chloride gave poly(EtSB‐block‐tBMA) with narrow molecular weight distributions. The t‐butyl ester groups in the obtained polymer were readily hydrolyzed via heating in 1,4‐dioxane in the presence of concentrated aqueous hydrochloric acid. The block copolymer with a short MAA segment was soluble in chloroform and insoluble in methanol and basic water, whereas the block copolymer with a long MAA segment was soluble in methanol and basic water and insoluble in chloroform. The block polymer (EtSB/tBMA = 45/60) formed a monolayer film on the water surface; this was confirmed by surface pressure measurement. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 86–92, 2001     

Poly(ϵ‐caprolactone)‐b‐poly(ethylene glycol)‐b‐poly(ϵ‐caprolactone) triblock copolymers: Synthesis and self‐assembly in aqueous solutions

Nontoxic and biodegradable poly(?‐caprolactone)‐b‐poly(ethylene glycol)‐b‐poly(?‐caprolactone) triblock copolymers were synthesized by the solution polymerization of ?‐caprolactone in the presence of poly(ethylene glycol). The chemical structure of the resulting triblock copolymer was characterized with ¹H NMR and gel permeation chromatography. In aqueous solutions of the triblock copolymers, the micellization and sol–gel‐transition behaviors were investigated. The experimental results showed that the unimer‐to‐micelle transition did occur. In a sol–gel‐transition phase diagram obtained by the vial‐tilting method, the boundary curve shifted to the left, and the gel regions expanded with the increasing molecular weight of the poly(?‐caprolactone) block. In addition, the hydrodynamic diameters of the micelles were almost independent of the investigated temperature (25–55 °C). The atomic force microscopy results showed that spherical micelles formed at the copolymer concentration of 2.5 × 10^?4 g/mL, whereas necklace‐like and worm‐like shapes were adopted when the concentration was 0.25 g/mL, which was high enough to form a gel. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 605–613, 2007     

Micelle formation induced by photo-Claisen rearrangement of poly(4-allyloxystyrene)-block-polystyrene

A novel micelle formation induced by the photo-Claisen rearrangement was attained using a poly(4-allyloxystyrene)-block-polystyrene (PASt-b-PSt) diblock copolymer. The photoreaction was performed in cyclohexane at room temperature without a catalyst. The conversion of the 4-allyloxystyrene units reached 90% by irradiation for 24 h. The photo-Claisen rearrangement of PASt-b-PSt into poly(3-allyl-4-hydroxystyrene)-block-PSt quantitatively proceeded up to a 20% conversion; however, the elimination of the allyl groups competitively occurred over the 20% conversion. The degrees of the photorearrangement and elimination showed good agreement in their material balance throughout the course of the reaction. Both of the photorearrangement and elimination finally reached ca. 50% degrees over 60% conversion. The light-scattering studies demonstrated that the PASt-b-PSt copolymer with a 36-nm hydrodynamic diameter as unimers formed micelles with a 98-nm diameter by irradiation.     

Shell-crosslinked nanoparticles through self-assembly of thermoresponsive block copolymers by RAFT polymerization

A reversible addition-fragmentation chain transfer (RAFT) agent, the methyl-2-(n-butyltrithiocarbonyl)propanoate (MBTTCP) has shown to be efficient in controlling the polymerization of N,N-dimethylacrylamide (DMA), N-isopropylacrylamide (NIPAM) and N-acryloyloxysuccinimide (NAS). Two different strategies have been studied to synthesize block copolymers based on one PNIPAN block and the other a random copolymer of DMA and NAS. When a PNIPAM trithiocarbonate-terminated is used as macromolecular chain transfer agent for the polymerization of a mixture of NAS and DMA, well-defined P(NIPAM-b-(NAS-co-DMA)) block copolymers were obtained with a low polydispersity index. These thermoresponsive block copolymers dissolved in aqueous solution at 25 °C and self-assembled into micelles when the temperature was raised above the LCST of the PNIPAM block. The micelle shell containing NAS units was further crosslinked using a primary diamine in order to get shell-crosslinked nanoparticles. Upon cooling below the LCST of PNIPAM this structure may easily reorganize to form nanoparticles with a water filled hydrophilic core.     

Thermosensitive t‐PLA‐b‐PNIPAAm tri‐armed star block copolymer nanoscale micelles for camptothecin drug release

Thermosensitive polylactide‐block‐poly(N‐isopropylacrylamide) (t‐PLA‐b‐PNIPAAm) tri‐armed star block copolymers were synthesized by atom transfer radical polymerization (ATRP) of monomer NIPAAm using t‐PLA‐Cl as macroinitiator. The synthesis of t‐PLA‐Cl was accomplished by esterification of star polylactides (t‐PLA) with 2‐chloropropionyl chloride using trimethylolpropane as a center molecule. FT‐IR, ¹H NMR, and GPC analyses confirmed that the t‐PLA‐b‐PNIPAAm star block copolymers had well‐defined structure and controlled molecular weights. The block copolymers could form core‐shell micelle nanoparticles due to their hydrophilic‐hydrophobic trait in aqueous media, and the critical micelle concentrations (CMC) were from 6.7 to 32.9 mg L^?1, depending on the system composition. The as‐prepared micelle nanoparticles showed reversible phase changes in transmittance with temperature: transparent below low critical solution temperature (LCST) and opaque above the LCST. Transmission electron microscopy (TEM) observations revealed that the micelle nanoparticles were spherical in shape with core‐shell structure. The hydrodynamic diameters of the micelle nanoparticles depended on copolymer compositions, micelle concentrations and media. MTT assays were conducted to evaluate cytotoxicity of the camptothecin‐loaded copolymer micelles. Camptothecin drug release studies showed that the copolymer micelles exhibited thermo‐triggered targeting drug release behavior, and thus had potential application values in drug controlled delivery. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4429–4439     

Synthesis of poly(4-vinyl pyridine-b-methyl methacrylate) by MAMA-SG1 initiated sequential polymerization and formation of metal loaded block copolymer inverse micelles

Well-defined poly(4-vinylpyridine) (P4VP) was synthesised by nitroxide-mediated radical polymerization using the BlocBuilder MAMA-SG1. The controlled character of the polymerization was confirmed by kinetic measurements and linear increase of the molar mass with monomer conversion. Poly(4-vinylpyridine) terminated with SG1 was then used as macroinitiator and chain extended to form poly(4-vinylpyridine-b-methyl methacrylate) and poly(4-vinylpyridine-b-(methyl methacrylate-co-styrene)) block copolymers. These block copolymers spontaneously organized into spherical inverse micelles in THF with critical micelle concentrations of 0.1 mg/mL for poly(4VP₁₉₀-b-MMA₉₁) and 0.01 mg/mL for poly(4VP₁₉₀-b-(MMA₅₇-co-S₁₈)) and sizes of 70 and 130 nm (DLS), respectively. The inverse micelles were loaded with copper(II)acetate leading to a slight increase in micelle size. The uniform structure of the inverse micelles was confirmed by FeSEM images, while the presence of copper in the micelle core was established by energy-dispersive X-ray spectroscopy (EDX) and FTIR spectroscopy.