Article pubs.acs.org/Macromolecules
Polymer Assemblies with Nanostructure-Correlated AggregationInduced Emission Meng Huo,†,‡ Qiquan Ye,† Hailong Che,† Xiaosong Wang,*,§ Yen Wei,*,‡ and Jinying Yuan*,† †
Key Lab of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Department of Chemistry, and ‡Key Lab of Bioorganic Phosphorus Chemistry & Chemical Biology of Ministry of Education, Department of Chemistry, Tsinghua University, 100084 Beijing, China § Department of Chemistry and Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue, N2L 3G1 Waterloo, Canada S Supporting Information *
ABSTRACT: The correlation of aggregation-induced emission (AIE) to the nanostructure of polymer assemblies was investigated. A series of AIE-active PDMA-b-P(BzMA-TPE) [PDMA: poly(N,Ndimethylaminoethyl methacrylate); P(BzMA-TPE): poly[benzyl methacrylate-co-1-ethenyl-4-(1,2,2-triphenylethenyl)benzene]] assemblies with controlled nanostructures were prepared via polymerization-induced self-assembly of BzMA and TPE, an AIEgen, in the presence of PDMA macro-chain-transfer agents. We found that the fluorescence intensity and fluorescent quantum yield increase in the order of vesicles > wormlike micelles > spherical micelles. For spherical micelles and vesicles, the AIE effect strengthens with increase in micellar size and wall thickness, respectively. As the AIE effect indicates the packing compactness of the AIEgens, the discovered structure-correlated emission can be attributed to the stress variation of polymer chains in the aggregates. AIE is therefore potentially useful as a probe for the investigation and understanding of nanostructure and evolution process of polymer self-assemblies.
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INTRODUCTION The nanostructure of assemblies is a critical factor that affects their biodistribution, circulation time in vivo, and the bioavailability of functional groups on their surface.1−6 Hence, it is of great interest to rationally design assemblies capable of functional regulation through well-controlled nanostructures. In particular, fluorescent assemblies with nanostructure-correlated photophysics have been under active investigation for their applications, including bioimaging, theranostic agents, sensors, and miniaturized optoelectronic devices.7−13 To date, a variety of fluorescent assemblies based on π-conjugated organic luminophores have been designed, whose photoluminescence properties could be facilely tuned by the supramolecular arrangement of fluorophores within the assemblies as well as their localized electronic environment.14−18 For example, Yao et al. synthesized an amphiphilic perylene diimide derivative with two pyridyl groups, which self-assembled into a platelike structure and subsequently transformed into vesicles upon protonation of the pyridyl groups.17 Accompanied by the morphological evolution, the supramolecular arrangement of perylene diimide changed; therefore, both the fluorescence intensity and quantum yield of the assemblies increased substantially. However, aggregation of π-conjugated organic luminophores in the assemblies may lead to severe quenching effect, which would restrict the brightness of the assemblies.19 Opposite to the aggregation-caused quenching effect, aggregation-induced emission (AIE) is a unique photophysical © 2017 American Chemical Society
phenomenon of a category of luminogenic molecules that emit weakly or are nonemissive in good solvents but are highly luminescent in the aggregated state.20−23 In the aggregated state, the restriction of intramolecular motion blocks the nonemissive pathway for the AIEgens to dissipate the exciton energy, leading to conspicuous enhancement of both the fluorescent intensity and quantum yield.24−29 Such photophysical mechanism makes AIE-active dyes superior probes for observing materials in their aggregated state. The assembly process could be imaged by the AIE mechanism, such as interfacial dynamic self-assembly, fibrillation of insulin and gelation process of chitosan, which may be problematic for the ordinary π-conjugated dyes to monitor.30−34 Specifically, the photoluminescence properties of AIEgens were reported to be related to the nanostructure of the assemblies.35 Tetraphenylethene was modified with two 2,6-pyridinedicarboxylate groups to form a bis-ligand, which slowly self-assembled into cocoonlike flat sheets by complexation with Ni2+ and subsequently transformed into nanoladders by adding the positively charged block polyelectrolyte. The morphology evolution of the assemblies could be indicated by the difference in AIE fluorescence of tetraphenylethene groups, which were sensitive to the changes in the surrounding microenvironment. Despite Received: November 17, 2016 Revised: January 3, 2017 Published: January 25, 2017 1126
DOI: 10.1021/acs.macromol.6b02499 Macromolecules 2017, 50, 1126−1133
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°C with THF (containing 2% triethylamine) as eluent at a flow rate of 1 mL min−1. The SEC system is composed of a Waters 1515 isocratic HPLC pump, three Styragel columns, and a 2414 refractive index detector. Monodispersed polystyrene standards were used for calibration. Dynamic Laser Scattering (DLS). A Marven Z90 Zetasizer equipped with a 633 nm He−Ne laser and an avalanche photodiode detector was used to characterize the hydrodynamic size of the selfassemblies. The scattering light at 90° angle was detected and used to analyze the size and distribution. Transmission Electron Microscopy (TEM). TEM images were recorded by a JEM-2010 microscope at 120 kV. To prepare TEM samples, 10 μL of sample was dropped onto a carbon-coated copper grid. After removing the excess solution by blotting paper, the samples were dried at ambient conditions. Fluorescence Spectroscopy. The fluorescent spectra were acquired using a PerkinElmer LS55 fluorescence spectrometer, with 2.5 nm slit width and 600 nm min−1 scan rate. The excitation wavelength was set as 360 nm for all the samples, and spectra shown were averaged from five scans. Fluorescent Quantum Yield (QY). The absolute fluorescent quantum yield of the self-assemblies was measured using a Hamamatsu C9920-11 system equipped with a 3.3 in. integrating sphere to eliminate the effect of scattering. The excitation wavelength was set as 360 nm, and QY measurement was repeated for three times for each sample. Confocal Laser Scanning Microscopy (CLSM). The morphology of the fluorescent assemblies was characterized in situ by an UltraView Vox 3D live cell imaging system equipped with a Yokogawa CSU-X1 spinning disk confocal scanner and an Olympus IX83 invert fluorescence microscope. A 405 nm laser diode was used as the excitation illuminant. Synthesis of PDMA Macro-CTAs. PDMA macro-CTAs with two different molecular weights were prepared by RAFT polymerization. For PDMA macro-CTA with a target degree of polymerization (DP) of 30, AIBN (0.25 mmol, 41 mg), CPADB (1.25 mmol, 349 mg), and DMAEMA (75 mmol, 11.8 g) were dissolved into 15 mL of 1,4dioxane and sealed in a Schlenk tube. After N2 purging for 15 min, the tube was placed into a 70 °C oil bath and polymerized for 3 h. 1H NMR analysis indicated that the conversion of the polymerization was 53%. After quenching in liquid nitrogen, the solution was poured into n-hexane to purify the polymer. The obtained PDMA macro-CTA with a DP of 39 as characterized by 1H NMR was denoted as PDMA39. SEC analysis showed the Mn for PDMA39 was 4500 g mol−1 and PDI was 1.18. In the case of PDMA macro-CTA with target DP of 75, AIBN (0.20 mmol, 33 mg), CPADB (1.0 mmol, 279 mg), and DMAEMA (150 mmol, 23.6 g) were dissolved into 12 mL of 1,4dioxane, and the monomer conversion reached to 64% after 3 h of polymerization. The DP for the resulting polymer was calculated to be 67 (denoted as PDMA67), and Mn was 10 700 g mol−1 (PDI = 1.19) as measured by SEC. RAFT Dispersion Copolymerization of BzMA and TPE. Fluorescent assemblies were prepared by RAFT dispersion copolymerization of BzMA and TPE mediated by PDMA macro-CTA with different molecular weights. Typically, AIBN (3.0 μmol, 0.5 mg), PDMA39 (15 μmol, 96 mg), BzMA (1.8 mmol, 317 mg), and TPE (0.3 mmol, 108 mg) were dissolved into 3.9 mL of ethanol and sealed in a Schlenk tube. After N2 purging for 15 min, the reaction mixture was polymerized at 70 °C for 24 h. After 24 h, a small aliquot was taken for monomer conversion measurement. The resulting dispersion of PDMA39-P(BzMA-TPE) assemblies was dialyzed against ethanol and H2O, respectively. With the same procedure, fluorescent micelles with different sizes were prepared using PDMA67 as the macro-CTA. During our experiments, the feed molar ratio of BzMA/PDMA was systematically varied while the molar ratio of TPE/PDMA was kept constant as 20. All the experiments were performed at 14.5% solids content.
these achievements, there is a lack of systematic study on the photoluminescence behaviors of these AIE-active assemblies in relation to their nanostructures. Polymerization-induced self-assembly (PISA) is an emerging technique to prepare polymer self-assemblies of different nanostructures with high concentration.36−40 It enables the preparation of polymeric self-assemblies in situ during the course of block copolymer polymerization in selected solvent. Polymeric self-assemblies of different nanostructures, such as spherical micelles, wormlike micelles, and vesicles, could be easily achieved by PISA.41−45 PISA could simplify the factors for size and morphology control and largely increase the concentration of self-assemblies, thus serving as a reliable and powerful platform for preparing polymer assemblies.46−53 We therefore envision that the developed PISA technique can be harnessed to reveal the correlation of nanostructures to the photoluminescence behaviors of AIE-active polymer assemblies by incorporating AIE-active fluorophores into the PISA system. Herein, AIE-active polymer assemblies with controllable size and morphology are prepared by reversible addition− fragmentation chain transfer (RAFT) polymerization of benzyl methacrylate (BzMA) and 1-ethenyl-4-(1,2,2-triphenylethenyl)benzene (TPE) mediated by poly(N,N-dimethylaminoethyl methacrylate) (PDMA) macro-chain-transfer agent (macroCTA) (Scheme 1). TPE contains a tetraphenylethene group, Scheme 1. Schematic Representation for the Preparation of AIE-Active Assemblies by PISA
which is an effective AIEgen. The photoluminescence resulted from the AIE of TPE groups varies as the nanostructure of the assemblies evolves, which is correlated to the packing density of the core-forming blocks. The combination of AIE and PISA is therefore a valuable technique to study the nanostructurecorrelated photophysical behavior.
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EXPERIMENTAL SECTION
Materials and Instrumentation. 1-Bromo-1,2,2-triphenylethylene, 4-vinylphenylboronic acid, tetrakis(triphenylphosphine)palladium, 2-(dimethylamino)ethyl methacrylate (DMAEMA), and benzyl methacrylate (BzMA) were purchased from Tokyo Chemical Industry (TCI). 2,2′-Azobis(2-methylpropionitrile) (AIBN) was purchased from J&K Scientific Ltd. and was refined by recrystallization. DMAEMA and BzMA were passed through a short alkaline alumina column before use to remove the inhibitor. 4-Cyanopentanoic acid dithiobenzoate (CPADB) was prepared as described previously.54 2-(4-Vinylphenyl)ethene-1,1,2-triyl)tribenzene (TPE) was prepared according to the literature.55 All other reagents were used as received. 1 H NMR Spectroscopy. All 1H NMR spectra were recorded on a 400 MHz JEOL JNM-ECA400 spectrometer at room temperature. Size-Exclusion Chromatography (SEC). The molecular weights and polydispersity index (PDI) of PDMA macro-CTAs and their copolymers were characterized by a Waters 1515 SEC system at 35 1127
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Figure 1. Size and morphology characterization of the PDMA39-P(BzMA-TPE)-x assemblies (x was the feed ratio of BzMA/PDMA) prepared by dispersion polymerization of BzMA and TPE. DLS intensity profiles of PDMA39-P(BzMA-TPE)-x assemblies (x = 120, 240, 360) in (a) EtOH and (b) H2O. (c−h) TEM images for PDMA39-P(BzMA-TPE)-x assemblies in EtOH and H2O: (c) PDMA39-P(BzMA-TPE)-120 in EtOH, (d) PDMA39-P(BzMA-TPE)-240 in EtOH, (e) PDMA39-P(BzMA-TPE)-360 in EtOH, (f) PDMA39-P(BzMA-TPE)-120 in H2O, (g) PDMA39-P(BzMATPE)-240 in H2O, (h) PDMA39-P(BzMA-TPE)-360 in H2O. CLSM images of (i) PDMA39-P(BzMA-TPE)-120, (j) PDMA39-P(BzMA-TPE)-240, and (k) PDMA39-P(BzMA-TPE)-360 in H2O.
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RESULTS AND DISCUSSION Dispersion Copolymerization of BzMA and TPE Mediated by PDMA Macro-CTA. RAFT dispersion copolymerization of BzMA and TPE (the AIE-active monomer) was performed in ethanol in the presence of PDMA39 or PDMA67 macro-CTA (Scheme S1). After the polymerization, the resultant colloids were transferred to water phase via dialysis. Both colloids in ethanol and water were examined using DLS and TEM. A fraction of the samples were purified for 1H NMR and SEC analysis. PISA for the Colloids with Varied Morphologies. The adding ratio of BzMA/PDMA was 120, 240, and 360, while the ratio of TPE/PDMA was 20 for all the polymerizations. The resultant colloids were named as PDMA39-P(BzMA-TPE)-x (x = 120, 240, 360). Table S1 illustrates the characterization of the molecular structures for the samples, where the TPE loading content is close to the adding amount of the monomers for all these samples. The colloidal samples were examined using DLS, TEM, and CLSM. The results are displayed in Figure 1. As shown in Figure 1a, DLS of these assemblies in ethanol shows
that the intensity-averaged hydrodynamic diameter (Dh) increases with the adding ratio of BzMA/PDMA. When the solvent for the assemblies was replaced by water, the intensityaveraged size in water were smaller than that in ethanol, as water is a poorer solvent than ethanol for P(BzMA-TPE) block (Figure 1b).56 The TEM images for the colloids in ethanol and water are displayed in Figures 1c−e and 1f−h, respectively. By comparing these two sets of images, the replacement of the solvent did not alter the morphology of the assemblies, which was in accordance with the reported literature.57 As expected, PISA polymerizations resulted in varied morphologies depending on the amount of adding monomers. For PDMA39P(BzMA-TPE)-120 with targeting DP of 120, spherical micelles with Dh of 41.3 ± 4.2 nm were obtained, while worm-like micelles of several micrometers in length and 51.7 ± 6.0 nm in diameter were observed for PDMA39-P(BzMA-TPE)-240. Further increasing the adding ratio of BzMA/PDMA to 360, vesicles of 186.2 ± 26.0 nm in diameter were prepared. As these assemblies were expected to be fluorescent, CLSM equipped with a spin disc scanner was used for the observation of these 1128
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Figure 2. AIE effect of PDMA39-P(BzMA-TPE)-x assemblies (x = 120, 240, 360). (a) FL spectra of PDMA39-P(BzMA-TPE)-120 in THF and in water. Concentration of TPE group was 5 μg mL−1 for both samples. Inset is the optical and fluorescent photographs of the PDMA39-P(BzMATPE)-120 assemblies. FL spectra of PDMA39-P(BzMA-TPE)-120, -240, and -360 assemblies in (b) H2O and (c) EtOH. Concentration of TPE group was 2.5 μg mL−1 for all the samples. (d) QY of PDMA39-P(BzMA-TPE)-x assemblies (micelles, worm-like micelles, and vesicles for x = 120, 240, and 360, respectively) in EtOH and H2O.
assemblies in situ (Figure 1i−k). PDMA39-P(BzMA-TPE)-120 micelles are too small to be imaged, so only dim fluorescent spot can be distinguished from the background (Figure 1i). PDMA39-P(BzMA-TPE)-240 assemblies become large enough and bright worm-like micelles could be easily imaged (Figure 1j). As for PDMA39-P(BzMA-TPE)-360, the CLSM image reveals larger and brighter spheres. We therefore conclude that photoluminescent PDMA39-P(BzMA-TPE) micelles, worm-like micelles, and vesicles have been prepared via PISA. PISA for Vesicles with Varied Wall Thicknesses. To prepare the vesicles of tunable wall thickness, PDMA39P(BzMA-TPE)-x (x = 450, 600, 800, 1200) with higher feed ratios of BzMA/PDMA were targeted. The resultant polymers were characterized by 1H NMR and SEC (Table S2). All these samples in EtOH and water appeared to be vesicles (Figures S1 and S2), which were similar to the morphology of PDMA39P(BzMA-TPE)-360. DLS analysis indicates that all the vesicles have similar size (Figure S3). However, as shown in the TEM images, wall thickness of these vesicles increases as a function of x. For PDMA39-P(BzMA-TPE)-800 and -1200, it becomes hard to distinguish the inner lumen of the vesicles. Wall thickness statistics of these vesicles obtained from their TEM images was plotted against the feed ratio of BzMA/PDMA, which clearly shows that wall thickness of vesicles increases with the target DP of PBzMA (Figure S4). PISA for the Spherical Micelles with Varied Sizes. PDMA macro-CTA with longer chain length was used to prepare spherical micelles with varied sizes. PISA copolymerization of BzMA and TPE was performed in the presence of PDMA67 macro-CTA. The feed ratio of BzMA/PDMA was varied from 100, 200, 300, 500, 700, 900 to 1200. The resultant copolymers were denoted as PDMA67-P(BzMAx-TPE)-x (x =
100, 200, 300, 500, 700, 900, 1200). The polymer structures and molecular weights were characterized by 1H NMR and SEC (Table S3). For all the samples, the number of repeat units for TPE is ca. 20. DLS characterization of the micelles manifest that the Dh of PDMA67-P(BzMAx-TPE)-x assemblies in ethanol are 38.5, 64.8, 80.6, 108.5, 124, 134.5, and 176.5 nm, following the x increase from 100 to 1200 (Figure S5a). Their morphologies as confirmed by TEM are spherical (Figure S5b− h). Following the same trend, Dh of PDMA67-P(BzMAx-TPE)x assemblies in H2O increases from 36.4 to 150.3 nm with x increasing from 100 to 1200, which is also confirmed by TEM characterization (Figures S6 and S7). Nanostructure Correlated AIE for PDMA-P(BzMA-TPE) Colloids. Morphology-Correlated AIE. The AIE effect was examined by comparing the fluorescence spectra of THF solution of PDMA39-P(BzMA-TPE)-120 block copolymer with its aqueous dispersion. As shown in Figure 2a, THF solution of PDMA39-P(BzMA-TPE)-120 block copolymer shows no fluorescence emission at 480 nm, while the aqueous dispersion of PDMA39-P(BzMA-TPE)-120 micelles has a strong fluorescence emission peak at 480 nm. Such marked spectral difference in fluorescence emission could be interpreted as an AIE effect due to the restriction of the intramolecular rotation of TPE moieties caused by aggregation. To quantitively compare the FL intensity, PDMA39-P(BzMA-TPE)-x (x = 120, 240, 360) assemblies were diluted, and the concentration of the TPE moieties was ensured to be the same for each solution. As shown in Figures 2b and 2c, it is obvious that the intensity of the emission for the assemblies in either water or EtOH varies as a function of the morphology of the assemblies. The intensity at 480 nm increases in the following order: PDMA39-P(BzMA-TPE)-120 (micelles) < 1129
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Figure 3. AIE properties of PDMA67-P(BzMA-TPE)-x micelles (x is the feed ratio of BzMA/PDMA, x = 100, 200, 300, 500, 700, 900, 1200) in H2O. (a) FL spectra (excited at 360 nm) of PDMA67-P(BzMA-TPE)-x micelles in H2O (2.0 μg mL−1). (b) FL emission maximum of PDMA67P(BzMA-TPE)-x micelles in H2O (2.0 μg mL−1) as a function of Dh of the micelles. (c) QY evolution of PDMA67-P(BzMA-TPE)-x micelles in H2O as a function of Dh of the micelles.
Figure 4. AIE properties of PDMA39-P(BzMA-TPE)-x vesicles (x is the feed ratio of BzMA/PDMA, x = 450, 600, 800, 1200) in H2O. (a) FL spectra (excited at 360 nm) of PDMA67-P(BzMA-TPE)-x micelles in H2O (2.0 μg mL−1). (b) FL emission maximum of PDMA39-P(BzMA-TPE)-x vesicles in H2O (2.0 μg mL−1) as a function of wall thickness of vesicles. (c) QY evolution of PDMA39-P(BzMA-TPE)-x vesicles in H2O as a function of wall thickness of vesicles.
size.58 As a result, the incident light absorbed by tetraphenylethene groups within the micelles decreases accordingly. We therefore measured the absolute QY that excludes the scattering effect. As shown in Figure 3c, the QY increases with the Dh of these assemblies and reaches 51.0% for PDMA67-P(BzMATPE)-1200 micelles. Such correlation reflects that the packing density of the core-forming blocks increases with the growth of the micelles during PISA. This micellar size-correlated AIE is also confirmed by PDMA67-P(BzMA-TPE) micelles in ethanol, whose fluorescence emission spectra and QY show similar trends with those in water (Figure S8). When the micelles assembled from PDMA67-P(BzMA-TPE)-x (x = 100, 200, 300, 500, 700, 900, 1200) are compared, QY in ethanol is lower than that in H2O. So the micelles are more compact in H2O. Wall Thickness Correlated AIE for the Vesicles. Fluorescence spectra for PDMA39-P(BzMA-TPE)-x (x = 450, 600, 800, 1200) vesicles under the same TPE concentration are similar, whereas the absolute QY for these vesicles is proportional to the wall thickness of the vesicles (Figure 4). The dispersion solvents have little effect on this correlation (Figure S9). It is therefore clear that the AIE effect strengthens with the increment of the thickness of the vesicular wall, suggesting that the increasing membrane stress within vesicles is enhanced during PISA. Interestingly, herein the correlation of the chain packing density within the membrane to the thickness of vesicles is actually opposite to the report of Hammer, who compared the membrane stress of two poly(ethylene oxide)-bpoly(butadiene) (PEO-b-PBD) vesicles of different wall thickness using porphyrin-based molecular rotors as the
PDMA39-P(BzMA-TPE)-240 (worm-like micelles) < PDMA39P(BzMA-TPE)-360 (vesicles). For the same polymers, the assemblies in water have stronger fluorescence emission than those in EtOH. To understand the effect of morphology and solvent on the AIE effect, the absolute QY of the assemblies in either EtOH or H2O was measured, and the results are illustrated in Figure 2d. QY is a pivotal parameter for AIE chromophores and reflects how tightly AIEgens aggregate. In the context of this work, the absolute QY could be considered as an indicator for the packing density of the polymer blocks within the assemblies. As shown in Figure 2d, QY of the assemblies in H2O is larger than that in EtOH because the core-forming blocks associate tightly in water. This result is in line with the lower solvation degree of P(BzMA-TPE) block in water as compared to the block in EtOH. In both dispersing solvents, QY increases following the morphology evolution from spherical, worm-like micelles to vesicles. This result suggests that the process of the nanostructure evolution tightens the chain packing and enhances the confinement of the AIEgens. Size-Correlated AIE for the Micelles. Figure 3a illustrates the fluorescence spectra for the aqueous dispersions of PDMA67P(BzMA-TPE) micelles with different sizes. Fluorescence emission intensity at 480 nm was plotted against the size of the micelles (Figure 3b). The emission intensity increases as the diameter of the micelles increases from 36.4 to 86.6 nm, while slightly decreases as the diameter increases from 86.6 to 150.3 nm, probably due to the scattering effect. It is well-known that the scattering of incident light increases with the micellar 1130
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Macromolecules sensor.12 As the twisting motion of molecular rotors is sensitive to the local membrane stress, PEO-b-PBD vesicles with thicker wall thickness provide more available volume for the internal rotation of these molecular rotors; thus, the membrane stress sensed by the molecular rotors is smaller. In contrast to the conventional self-assembly process, our study indicates that as the growth of vesicular wall during PISA, stacking of coreforming chains becomes more compact; hence, the volume available for TPE moiety turns constrained. Such difference exhibits the unique growth mechanism of self-assemblies during PISA.
assistance of using the UltraView Vox 3D live cell imaging system.
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CONCLUSION In summary, AIE-active PDMA-P(BzMA-TPE) assemblies with varied sizes and morphologies were readily prepared by RAFT dispersion copolymerization, and the correlation of AIE effect to the nanostructures of these assemblies was thus demonstrated. The fluorescence intensity and QY increase in the order of vesicles > worm-like micelles > spherical micelles. For spherical micelles, the AIE effect strengthens with the increment of micellar size. Such structure-correlated optical property is related to the stress variation of core-forming chains in the aggregates. While the aggregates evolve from small sphere to larger sphere, wormlike rods, and vesicles, the stress of the core-forming chains enhances, resulting in increased AIE emission. Besides, QY of the vesicles increases proportionally to the thickness of the vesicular walls, suggesting that membrane stress increases as the growth of vesicles during PISA, which is contrast to the vesicles obtained by traditional methods. Our study demonstrates the possibility of AIE as an effective probe for the investigation and understanding of polymer assemblies.
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ASSOCIATED CONTENT
* Supporting Information S
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.macromol.6b02499. Molecular characterization of PDMA39-P(BzMA-TPE) and PDMA67-P(BzMA-TPE) copolymers, DLS, TEM, and photoluminescence characterization of PDMA67P(BzMA-TPE) micelles and PDMA39-P(BzMA-TPE)-x (x = 450, 600, 800, 1200) vesicles (PDF)
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REFERENCES
AUTHOR INFORMATION
Corresponding Authors
*E-mail
[email protected] (X.W.). *E-mail
[email protected] (Y.W.). *E-mail
[email protected] (J.Y.). ORCID
Jinying Yuan: 0000-0002-1667-9252 Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS The National Natural Science Foundation of China (21374053, 51573086) and the Opening Project of State Key Laboratory of Polymer Materials Engineering (Sichuan University) (Grant No. sklpme2014-4-26) are acknowledged for financial support. Y. Liu and Z. Liu are acknowledged for their help on the fluorescent quantum yield measurement. Y. Zhang in the Technology Center, Tsinghua University, is acknowledged for 1131
DOI: 10.1021/acs.macromol.6b02499 Macromolecules 2017, 50, 1126−1133
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DOI: 10.1021/acs.macromol.6b02499 Macromolecules 2017, 50, 1126−1133
