Efficient Access to Inverse Bicontinuous Mesophases via Polymerization-Induced Cooperative Assembly

Abstract

Open AccessCCS ChemistryRESEARCH ARTICLE1 Aug 2021Efficient Access to Inverse Bicontinuous Mesophases via Polymerization-Induced Cooperative Assembly Fei Lv, Zesheng An and Peiyi Wu Fei Lv State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Key Laboratory for Molecular Enzymology and Engineering of Ministry of Education, School of Life Sciences, Jilin University, Changchun 130012 State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, Laboratory of Advanced Materials, Fudan University, Shanghai 200433 , Zesheng An *Corresponding authors: E-mail Address: [email protected] E-mail Address: [email protected] State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Key Laboratory for Molecular Enzymology and Engineering of Ministry of Education, School of Life Sciences, Jilin University, Changchun 130012 and Peiyi Wu *Corresponding authors: E-mail Address: [email protected] E-mail Address: [email protected] State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, Laboratory of Advanced Materials, Fudan University, Shanghai 200433 State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Chemistry, Chemical Engineering and Biotechnology, Center for Advanced Low-Dimension Materials, Donghua University, Shanghai 201620 https://doi.org/10.31635/ccschem.020.202000407 SectionsSupplemental MaterialAboutAbstractPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail Polymerization-induced cooperative assembly (PICA) is reported to efficiently access inverse bicontinuous mesophases within particles consisting of amphiphilic block copolymers (BCPs) and solvophobic copolymers. Reversible addition-fragmentation chain transfer (RAFT) dispersion alternating copolymerization of styrene and pentafluorostyrene is conducted in 2% v/v toluene/ethanol by simultaneously using poly(N,N-dimethylacrylamide) (PDMA29) as a macromolecular chain transfer agent (macro-CTA) and small molecule CTA. The polymerization kinetics of PICA and polymerization-induced self-assembly (PISA) were compared, and the apparent rate constants observed in both systems were essentially the same. Gel permeation chromatography (GPC) indicated that PICA-synthesized amphiphilic BCPs/solvophobic copolymers had low dispersity. PICA syntheses were conducted by systematically varying the degree of polymerization of the core-forming block/solvophobic copolymer at different CTA molar ratios (x) and solid contents. The particle morphology was investigated by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and small-angle X-ray scattering (SAXS). Inverse bicontinuous mesophases could be accessed at different x and solid contents, demonstrating that PICA promoted the formation of inverse bicontinuous mesophases more effectively, compared with PISA. Download figure Download PowerPoint Introduction Particles with ordered inverse mesophases have shown great promise in biomaterials, nanotemplates, and bioreactors due to their bicontinuous channels, high surface area, and high porosity.1,2 Polymer mesophasic particles are typically prepared by solution self-assembly of highly asymmetric block copolymers (BCPs)3,4 for which the particle morphology is determined by the packing parameter p = v/a0lc ( v ,a0, and lc represent the volume of the core-forming block, the interfacial area, and the length of the core-forming block, respectively).5,6 By varying the p values along with other conditions, various morphologies such as sphere, worm, vesicle, and lamellae can be accessed readily at p ≤ 1. In principle, inverse bicontinuous mesophases such as cubosome and hexasome can also be accessed provided that the conditions for p > 1 are met. However, these inverse morphologies have been much less reported, presumably due to their elusive formation mechanism and complex assembly conditions. Eisenberg's group7 observed the formation of hexasomes in 1997 by solution self-assembly of poly(acrylic acid)-b-polystyrene. Since then, great progress has been made in the preparation of particles with inverse bicontinuous mesophases using different types of BCPs.8–16 For instance, Kim's group9,11,12,16 reported a series of inverse bicontinuous mesophases by solution self-assembly of dendritic linear and bottlebrush BCPs. Using linear BCPs, Mai's group14 prepared cubosomes and hexasomes successfully with a simple linear polystyrene‐b‐poly(ethylene oxide) BCP, while Shen's group15 prepared polymer cubosomes and hexasomes via self-assembly of a rod-coil BCP. Although solution self-assembly is a highly versatile and well-established method for preparing polymeric particles of various morphologies, it typically suffers a low efficiency due to multistep synthesis and low-concentration self-assembly procedures. As a complementary method to solution self-assembly, polymerization-induced self-assembly (PISA) has gained much attention recently.6,17–26 PISA combines polymerization and in situ self-assembly of BCPs and can be conducted at high concentrations. As such, PISA has gained widespread use in the preparation of polymer particles of various morphologies by employing controlled/living polymerization techniques.19,27–65 Despite great success, PISA generation of inverse bicontinuous mesophases has rarely been achieved. Pan's group66 reported the first example of an ordered inverse bicontinuous mesophase via PISA of poly(2-dimethylaminoethyl methacrylate)-b-polystyrene. Armes group67 reported the formation of disordered bicontinuous mesophases via PISA of poly(N,N-dimethylacrylamide)-b-poly(styrene-alt-N-phenylmaleimide) in which the core-forming block is an alternating copolymer. We also employed PISA to generate ordered inverse bicontinuous mesophases in reversible addition-fragmentation chain transfer (RAFT) dispersion alternating copolymerization of styrene (St) and pentafluorostyrene (PFS),68 and dispersion polymerization of 4-tert-butoxystyrene.69 A successful access to these inverse bicontinuous mesophases serving as a testament is that PISA is a viable approach for preparing particles with rare morphologies. However, the few examples reported so far also highlight the challenges of using PISA to generate inverse mesophases. Therefore, it is highly desirable to develop novel strategies to promote efficient access to inverse bicontinuous mesophases. To this end, we employed polymerization-induced cooperative assembly (PICA)70 to prepare particles with ordered bicontinuous cubosomes/hexasomes and demonstrated that PICA is more effective than PISA in accessing these rare morphologies. Experimental Methods Materials Styrene analytical reagent (St AR) grade was purchased from Sinopharm Chemical Reagent (Shanghai, China), 2,3,4,5,6-pentafluorostyrene (PFS; 97%) and N,N-dimethylacrylamide (DMA; 99%) from J&K Scientific (Shanghai, China) were passed through an alkaline aluminum oxide column to remove the inhibitor. 2,2′-Azobis(2-methylpropionitrile) (AIBN; 99%) from Sigma-Aldrich (Shanghai, China) was recrystallized from ethanol before use. The 2-ethylsulfanylthiocarbonylsulfanylpropionic acid methyl ester was synthesized according to a previous report.71 Ethanol (AR), N,N-dimethylformamide (DMF; AR), toluene (AR), tetrahydrofuran (THF; AR), and 1,4-dioxane (AR) from Sinopharm Chemical Reagent were used without further purification. Characterization Nuclear magnetic resonance spectroscopy Proton nuclear magnetic resonance (1H NMR) spectroscopy was conducted on a Bruker AV 400 MHz spectrometer (Bruker, Switzerland) using CDCl3 as the solvent. Chemical shifts were obtained using solvent residue as the reference. The monomer conversion was calculated using the cosolvent toluene as an internal standard. Transmission electron microscopy Transmission electron microscopy (TEM) was conducted on a JEM-1400 Plus Microscope (JEOL Ltd., Tokyo, Japan) at 120 kV, and high-resolution TEM was performed on a JEOL JEM2011F Microscope (Tokyo, Japan) at 200 kV. TEM samples were prepared by dropping 10 μL dispersion (0.05% or 0.1%, w/v) on a carbon-coated copper grid and dried at room temperature and then further dried under vacuum at 40 °C for 12 h. Gel permeation chromatography Gel permeation chromatography (GPC) was performed on an Agilent 1260 Infinity with a Waters 2410 refractive index detector (Agilent, America). The calibration curve was determined using monodisperse poly(styrene) (PS) (molecular weight range from 5.8 × 103 to 8.53 × 105 g mol−1) using THF as the mobile phase. The flow rate of THF was 1.0 mL min−1 at 35 °C. Field-emission scanning electron microscopy Field-emission scanning electron microscopy (FESEM) was performed on a Zeiss Ultra 55 (Zeiss, German) at a working voltage of 20 kV. Dispersions were diluted to 0.1% w/v and dropped onto mica sheet attached to steel stubs using carbon adhesive and then dried under vacuum at 40 °C for 5 h. The samples were made conductive by sputtering a thin layer of gold. Small-angle X-ray scattering Small-angle X-ray scattering (SAXS) profiles were recorded on a France/Xenocs XeUSS2.0 (Xenocs, France), with microfocus liquid metal anodes Ga alloy at 70 kV. The experiments were carried out through X-ray radiation with a wavelength of λ = 1.34 Å at room temperature (25 °C). To prepare the SAXS samples, 0.5 mL BCP dispersions were dropped on glass slides and dried at room temperature for 12 h and then further dried under vacuum at 25 °C for 2 h. Synthetic procedures Synthesis of PDMA29-b-P(St-alt-PFS)m BCP particles via PISA Poly(N,N-dimethylacrylamide) (PDMA29)-b-P(St-b-PFS)m BCP particles were synthesized by RAFT dispersion polymerization in toluene/ethanol (2/98, v/v) at 30% solid content and 70 °C. A typical procedure is described as follows: PDMA29 (26.2 mg, 0.0085 mmol), St (200.3 mg, 1.92 mmol), PFS (373.2 mg, 1.92 mmol), and AIBN (32 μL, 0.0131 g mL−1 in 2% v/v toluene/ethanol, 2.56 μmol) were dissolved in 2% v/v toluene/ethanol (2 mL). The solution was then degassed with N2 for 15 min in an ice/water bath and heated to 70 °C for 48 h. More 2% v/v toluene/ethanol (5 mL) was added to the reaction solution (1 mL), followed by centrifugation (8000 rpm, 10 min). The solids were washed three times with 2% v/v toluene/ethanol to give the copolymers for 1H NMR, 19F NMR, and GPC analysis. 1H NMR (400 MHz, CDCl3, δ [ppm]): 6.82–7.21 (br, He, Hf), 6.31–6.79 (br, Hg), 2.78–3.19 (Hh), 2.11–2.78 (br, Ha, Hc, Hi), 1.45–2.11 (Hb, Hd), 0.82–1.41 (Hj). Residual peak: 1.56 ppm was H2O. 19F NMR (376 MHz, CDCl3, δ [ppm]):−142 (Fa), −157 (Fc), −163 (Fb). Synthesis of PDMA29-b-P(St-alt-PFS)m/P(St-alt-PFS)m BCP/solvophobic copolymer blend particles via PICA PDMA29-b-P(St-alt-PFS)m/P(St-alt-PFS)m blend particles were synthesized by RAFT dispersion polymerization in toluene/ethanol (2/98, v/v) at 70 °C. A typical procedure is described as follows: PDMA29 (21.0 mg, 0.0068 mmol), CTA (0.65 mg, 0.0029 mmol), St (201.9 mg, 1.94 mmol), PFS (376.4 mg, 1.94 mmol), and AIBN (28 μL, 0.0172 g mL−1 in 2% v/v toluene/ethanol, 2.91 μmol) were dissolved in 2% v/v toluene/ethanol (2 mL). The solution was degassed with N2 for 15 min in an ice/water bath and heated to 70 °C for 48 h. More 2% v/v toluene/ethanol (5 mL) was added to the reaction solution (1 mL), followed by centrifugation (8000 rpm, 10 min). The solids were washed three times with 2% v/v toluene/ethanol to give the polymers for 1H NMR, 19F NMR, and GPC analysis. 1H NMR (400 MHz, CDCl3, δ [ppm]): 6.78–7.21 (br, He, Hf, He', Hf'), 6.28–6.78 (br, Hg, Hg'), 2.80–3.19 (Hh), 1.98–3.19 (br, Ha, Hc, Hi, Ha', Hc'), 1.37–1.98 (Hb, Hd, Hb', Hd'), 0.74–1.39 (Hj). 19F NMR (376 MHz, CDCl3, δ [ppm]): −139 to 143 (Fa, Fa'), −154 to 160 (Fc, Fc'), −161 to 165 (Fb, Fb'). Results and Discussion As an extension to PISA, PICA can facilitate morphological transitions via simultaneous use of macromolecular chain transfer agents (macro-CTAs) and small molecule CTAs,70,72,73 leading to the generation of amphiphilic BCPs and solvophobic copolymers that cooperatively assemble in the same particles. As depicted in Schemes 1a and 1b, a trithiocarbonate was used as a small molecule CTA, and PDMA29 (Mn = 3.1 kg/mol, Đ = 1.10), synthesized via RAFT polymerization from the same CTA, was used as a solvophilic macro-CTA or stabilizer. Mixtures of the small molecule CTA and PDMA29 macro-CTA were used to mediate RAFT dispersion alternating copolymerization of electron-rich St and electron-deficient PFS at 70 °C. Thus, this PICA approach generated colloidal particles consisting of PDMA-b-P(St-alt-PFS) BCPs and P(St-alt-PFS) copolymers in the same particles. PICA was conducted in 2% v/v toluene/ethanol since this solvent composition has been demonstrated previously to be effective in PISA to obtain ordered inverse mesophases based on dispersion alternating copolymerization of St and PFS.68 PICA was first conducted at a total solid content of 30% w/v using 0.3 equiv. AIBN by controlling the molar ratio of small molecule CTA (x) at x = 0.3. The comparison of polymerization kinetics of PICA versus PISA is shown in Figure 1a. Both PICA and PISA syntheses exhibited pseudo-first-order kinetics, indicating the presence of a constant radical concentration in both cases. Multistaged polymerization kinetics are often observed in some PISA systems because of polymerization locus transitions from solution to particles of different morphologies.29,36 However, multistaged transitions in polymerization kinetics were not observed in PISA or PISA, presumably due to the fast nucleation of the fluorine-containing core-forming block/solvophobic copolymer. The apparent polymerization rate constant for PICA (k = 0.128 h−1) was quite close to that for the PISA synthesis (k = 0.121 h−1), which means that the BCPs and solvophobic copolymers grew at the same rate considering that the AIBN concentration used for PICA (2.56 mmol L−1) and PISA (2.58 mmol L−1) was almost the same. Therefore, it is safe to assume that both PDMA29-b-P(St-alt-PFS)m BCPs and P(St-alt-PFS)m copolymers possessed nearly the same degree of polymerization (DP) during PICA. PICA syntheses (x = 0.3) targeting DPs in the range 100–400 all resulted in stable particles with near-quantitative monomer conversions (≥95%) ( Supporting Information Table S1). Although a mixture of BCPs and solvophobic copolymers was present in the PICA-generated particles, the overall molecular weight distribution was relatively low (Đ ≤ 1.20), as indicated by GPC measurements (Figure 1b). This suggests that PICA proceeds with good RAFT control, and the difference in molecular weight between BCPs and solvophobic copolymers was relatively small due to the low molecular weight of PDMA29. 1H NMR spectroscopy analysis ( Supporting Information Figure S1) indicated that PICA-generated particles had a higher integration ratio of aromatic protons (6.2–7.2 ppm) to N-methyl protons (2.8–3.2 ppm) than the corresponding PISA-generated particles. An apparent increase in the 19F signal was observed in 19F NMR spectra for the PICA sample relative to the PISA sample. These results confirmed that both PDMA29-b-P(St-alt-PFS)m BCPs and P(St-alt-PFS)m copolymers were produced in PICA. Scheme 1 | PICA to access inverse bicontinuous mesophases: (a) RAFT dispersion alternating copolymerization of St and PFS using a mixture of macro-CTA and small molecule CTA and (b) morphological transition sequence with increasing DP (m). PICA, polymerization-induced cooperative assembly; RAFT, reversible addition-fragmentation chain transfer; St, styrene; PFS, pentafluorostyrene; macro-CTA, macromolecular chain transfer agent; DP, degree of polymerization. Download figure Download PowerPoint Having established that RAFT dispersion PICA of PDMA29-b-P(St-alt-PFS)m/P(St-alt-PFS)m could produce colloidally stable particles with well-controlled composition and molecular weight, we next focused our attention on the particle morphologies, which were investigated by TEM and scanning electron microscopy (SEM). For the convenience of comparison, the TEM micrographs for the PISA-generated particles68 are provided in Supporting Information Figure S2. At x = 0.3 and 30% w/v solid content, the morphological transition with increasing DPs of the core-forming block/solvophobic copolymer of PICA-generated particles underwent with a sequence of a sphere–worm–vesicle–sponge–inverse bicontinuous mesophase (Figures 2a–2i), similar to that observed in PISA. Specifically, spheres with a diameter of 36.2 ± 7.5 nm, worms with a diameter of 32.7 ± 5.6 nm, vesicles with diameters of 434.6 ± 121.7 nm, and a wall thickness of 48.6 ± 13.5 nm were observed at DPs of 100, 130, and 180, respectively. Sponge-like particles started to form when DP increased to 250, beyond which the formation of inverse bicontinuous mesophases at DP ≥ 300 was evident. High-resolution TEM confirmed the presence of ordered mesophases with a solvophobic polymer channel diameter of 26.5 ± 4.8 nm and a hollow channel diameter of 33.4 ± 5.2 nm. SEM indicated that the bicontinuous structures were wrapped by a rough surface membrane (∼32 nm). Noticeably, inverse bicontinuous mesophases started to form at a lower DP for PICA (DP 300) than for PISA (DP 450), demonstrating that PICA was more efficient in accessing inverse bicontinuous mesophases than PISA. Figure 1 | (a) Pseudo-first-order polymerization kinetics of PISA and PICA (x = 0.3) targeting DP 450, (b) GPC traces of PICA (x = 0.3) targeting different DPs. Experiments were conducted in 2% v/v toluene/ethanol at 30% w/v solid content and 70 °C. PISA, polymerization-induced self-assembly; PICA, polymerization-induced cooperative assembly; DP, degree of polymerization; GPC, gel permeation chromatography. Download figure Download PowerPoint Unlike PISA, it was possible to adjust the molar ratio of CTA to modulate particle morphology in PICA, which led us to examine varying two more CTA molar ratios (x = 0.1 and 0.6) at the same solid content (30% w/v). The TEM micrographs for PICA conducted at x = 0.1 are shown in Figures 3a–3i. The morphological transition for this series of particles is similar to that for PISA, as might be expected considering the relatively low CTA molar ratio. However, the effect of PICA on promoting morphological transition was still discernable even at this low CTA molar ratio (x = 0.1). For instance, sponge-like particles formed at DP 300 for PICA (x = 0.1), whereas DP 400 was required to create the same PISA morphology. Obviously, a higher CTA molar ratio had a more profound effect on promoting morphological transition, as inverse mesophases were observed at a DP as low as 300 for PICA conducted at x = 0.3, but inverse mesophases were obtained at DPs ≥ 400 for PICA (x = 0.1), as judged from the rim of the micron-sized particles and high-resolution TEM. Figure 2 | TEM (a–h) and SEM (i) micrographs of PICA-synthesized particles at x = 0.3 and 30% w/v solid content. TEM, transmission electron microscopy; SEM, scanning electron microscopy; PICA, polymerization-induced cooperative assembly. Download figure Download PowerPoint The TEM micrographs for PICA conducted at x = 0.6 are shown in Figures 4a–4f. Such a high CTA molar ratio showed a more significant effect on promoting morphological transition than CTA molar ratios of 0.1 and 0.3. Sponge-like morphology occurred at a much lower DP of 180. Inverse mesophases, albeit less ordered, appeared more readily at DP of 250 ( Supporting Information Figure S4). As the DP further increased to 300, the internal mesophase became more ordered than those obtained at lower DPs within this series (x = 0.6, 30% w/v), as revealed by high-resolution TEM (inset of Figure 4e). Figure 3 | (a–i) TEM micrographs of PICA-synthesized particles at x = 0.1 and 30% w/v solid content. TEM, transmission electron microscopy; PICA, polymerization-induced cooperative assembly. Download figure Download PowerPoint We reported previously that high solid contents, at least 30% w/v, were required to obtain inverse bicontinuous mesophases for PISA.68 To further illustrate the capacity of PICA for promoting morphological transition, we decided to conduct PICA syntheses at lower solid contents to see if inverse mesophases could still be achieved. Two series of PICA (x = 0.3) syntheses were conducted at 20% and 10% w/v solid content, respectively, and their TEM micrographs are presented in Figures 5a–5f and 6a–6f. For all PICA (x = 0.3) conducted at 30–10% w/v, the morphological transition sequence followed the same pattern, but increasingly higher DPs were required to obtain the same morphology due to decreasing solid content, and thus, lower probability of inelastic collision between particles. For instance, at DP 130, worms were observed for both 30% and 20% w/v solid contents, but spheres were observed for 10% w/v solid content. A higher DP 180 was required for 10% w/v solid content to reach the worm phase, and the worms were shorter than those for 30% and 20% solid contents. Nevertheless, it is remarkable to see that inverse mesophases could be accessed even when the solid content was lowered. Inverse mesophases occurred at DP 250 and 350 for 20% and 10% w/v solid content, respectively. Note that as the solid content decreased, the mesophases became less ordered, as revealed by high-resolution TEM. We also conducted PICA (x = 0.6) synthesis by lowering the solid content from 30% to 10% w/w. A similar trend was observed, and inverse mesophases were again observed at 10% w/v solid content ( Supporting Information Figure S5). Figure 4 | (a–f) TEM micrographs of PICA-synthesized particles at x = 0.6 and 30% w/v solid content. TEM, transmission electron microscopy; PICA, polymerization-induced cooperative assembly. Download figure Download PowerPoint We elucidated the PICA-generated particles' internal mesophasic structures by performing SAXS and SAXS profiles for some of the representative samples are shown in Figure 7. We reported earlier that the mesophases of PISA-generated particles evolved from Im3m to mixed Im3m and p6 mm structures as the DP of the core-forming block increased.68 In this study, all the PICA-generated particles possessed mixed Im3m and p6 mm symmetries. Noteworthily, only one peak (q1), assigned to the 10 faces of p6 mm, appeared in all these particles. In principle, a specific mesophasic structure could not be explicitly assigned based on only one SAXS peak. This somewhat arbitrary assignment of q1 to p6 mm is based on the mixed Im3m and p6 mm structures observed in the PISA-generated particles and different microdomains in the PICA-generated particles, as revealed by high-resolution TEM. In Figure 7b, in addition to the q1 peak assigned to p6 mm, the SAXS profile also shows two other distinct peaks (q3 and q4) with a defined q2 ratio of 1/2, which could be assigned to Im3m phase. Particles with well-defined Im3m phase typically possesses ordered pores on the surface.9,74,75 However, the surface of these particles did not possess any pores but showed some parallel aligned valleys, indicating that Im3m may be present at a than p6 This was by the that to the at the of the particles, as as parallel to the could be also that SAXS peaks of p6 mm phase were relatively less than those for Im3m phase, even p6 mm structures were observed by Therefore, peaks corresponding to Im3m phase appeared in the SAXS it is that Im3m for a and the be assigned to the p6 mm phase. The SAXS peaks in Figures and were less indicating the mesophases generated at x = 0.1 and 0.6 were less ordered, with the from TEM. Figure | (a–f) TEM micrographs of PICA-synthesized particles at x = 0.3 and 10% w/v solid content. TEM, transmission electron microscopy; PICA, polymerization-induced cooperative assembly. Download figure Download PowerPoint We have investigated PICA of systematically by varying the CTA molar ratio DP of the core-forming block/solvophobic and the solid content ( Supporting Information Table PICA exhibited pseudo-first-order polymerization with an apparent polymerization rate constant close to that of PISA, polymerization of BCPs and solvophobic and thus, a distribution of polymer within the particles. As DP of the core-forming block/solvophobic copolymer morphological transitions followed the sequence of a bicontinuous inverse bicontinuous mesophases, Im3m and p6 mm were observed in all PICA syntheses conducted at different x 0.3, and 0.6) and solid contents and 30% w/v), which the mesophases obtained at x = 0.3 and 30% w/v showed the Therefore, we that PICA could promote morphological transition an effective method for particles with inverse bicontinuous mesophases. be to the and of inverse bicontinuous mesophases, which could be by of the conditions. Figure | SAXS profiles of representative PICA-generated particles with inverse bicontinuous mesophases in is for p6 mm and in the is for small-angle X-ray transmission electron microscopy; PICA, polymerization-induced cooperative assembly. Download figure Download PowerPoint Supporting Information Supporting Information is Figure 5 | (a–f) TEM micrographs of PICA-synthesized particles at x = 0.3 and 20% w/v solid content. TEM, transmission electron microscopy; PICA, polymerization-induced cooperative assembly. Download figure Download PowerPoint of The by the of and and the for the are 1. the of Bicontinuous The of of and of Armes of Polymerization-Induced 7. Structure of by of with Bicontinuous from a Inverse Bicontinuous of with Particles with and An of

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