pH Effect on Particle Aggregation of Vanillin End-Capped Polylactides Bearing a Hydrophilic Group Connected by a Cyclic Acetal Moiety.

To enhance the pH-responsiveness of poly(lactic acid) (PLA) particles, desired vanillin acetal-based initiators were synthesized and functional PLA was initiated at the chain end. PLLA-V6-OEG3 particles were prepared using polymers with various Mn values of 2400-4800 g/mol. PLLA-V6-OEG3 was appropriated to achieve a pH-responsive behavior under physiological conditions within 3 min via the six-membered ring diol-ketone acetal. Moreover, it was found that the polymer chain length (Mn) influenced the aggregation rate. TiO2 was selected as the blending agent to improve the aggregation rate. The PLLA-V6-OEG3 blended with TiO2 was found to accelerate the aggregation rate compared with that without TiO2, and the best ratio of polymer/TiO2 was 1:1. To study the effect of the chain end for stereocomplex polylactide (SC-PLA) particles, PLLA-V6-OEG4 and PDLA-V6-OEG4 were successfully synthesized. The obtained results of SC-PLA particle aggregation implied that the types of chain end and the molecular weight of polymer could influence the aggregation rate. The SC-V6-OEG4 blended with TiO2 could not make our target to aggregate under physiological conditions within 3 min. This study motivated us to control the particle aggregation rate under physiological conditions for applying as a target drug carrier which is significantly influenced by not only the molecular weight but also the hydrophilicity of the chain-end as well as the number of acetal bonds.

Synthesis of a novel carboxybetaine copolymer with different spacer lengths and inhibition of nonspecific protein adsorption on its polymer film.

Herein, we designed and synthesized a thermally stable carboxybetaine copolymer with a one- or three-carbon spacer between ammonium and carboxylate groups (CBMA1 and CBMA3) to create an anti-nonspecific adsorption surface with the ability to immobilize antibodies. A series of controlled poly(N,N-dimethylaminoethyl methacrylate) was successfully prepared using reversible addition-fragmentation chain-transfer (RAFT) polymerization and was derived to carboxybetaine copolymers of poly(CBMA1-co-CBMA3) [P(CBMA1/CBMA3)] with various CBMA1 contents, including the homopolymers of CBMA1 and CBMA3. Thermal stability of the carboxybetaine (co)polymers was higher than that of the carboxybetaine polymer with a two-carbon spacer (PCBMA2). Further, we also evaluated nonspecific protein adsorption in fetal bovine serum and antibody immobilization on the substrate coated with P(CBMA1/CBMA3) copolymers using surface plasmon resonance (SPR) analysis. As the CBMA1 content increased, nonspecific protein adsorption on the P(CBMA1/CBMA3) copolymer surface decreased. Similarly, the immobilization amount of the antibody decreased as the CBMA1 content increased. However, the figure of merit (FOM), defined as the ratio of the amount of antibody immobilization to that of nonspecific protein adsorption, depended on the CBMA3 content; FOM was higher when the CBMA3 content was 20-40% than those of CBMA1 and CBMA3 homopolymers. These findings will help enhance the sensitivity of the analysis using molecular interaction measurement devices, such as SPR and quartz crystal microbalance.

Tailor-Made Poly(vinylamine) via Purple LED-Activated RAFT Polymerization of N-vinylformamide.

Photo-iniferter reversible addition-fragmentation chain transfer (PI-RAFT) polymerization of N-vinylformamide (NVF) is demonstrated by using purple light. PNVFs with predetermined molar masses and narrow molar mass distributions are obtained. High RAFT chain-end fidelity is confirmed by matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) and electrospray-ionization time-of-flight mass spectrometry (ESI-TOF-MS), and chain extension experiment. To demonstrate the potential of this approach, an original poly(N-vinylpyrrolidone)-b-poly(N-vinylformamide) (PVP-b-PNVF) diblock copolymer is synthesized and characterized by aqueous size-exclusion chromatography (SEC), asymmetric flow field-flow fractionation (A4F), and 1 H diffusion-ordered spectroscopy nuclear magnetic resonance (1 H DOSY NMR). Finally, selective hydrolysis of PNVF block to corresponding pH-responsive poly(N-vinylpyrrolidone)-b-poly(N-vinylformamide) (PVP-b-PVAm) is performed.

Validation study for in vitro skin irritation test using reconstructed human skin equivalents constructed by layer-by-layer cell coating technology.

The aim of this study is to validate an in vitro skin irritation test (SIT) using three-dimensional reconstructed human epidermal (RhE) skin equivalents prepared by layer-by-layer (LbL) method (LbL-3D Skin) in a series of interlaboratory studies. The goal of these validation studies is to evaluate the ability of this in vitro test to reliably discriminate skin irritant from nonirritant chemicals, as defined by OECD and UN GHS. This me-too validation study is to assess the within- and between-laboratory reproducibility, as well as the predictive capacity, of the LbL-3D Skin SIT in accordance with performance standards for OECD TG 439. The developed skin model, LbL-3D Skin had a highly differentiated epidermis and dermis, similar to the validated reference methods (VRM) and native human skin. The quality parameters (cell survival in controls, tissue integrity, and barrier function) were similar to VRM and in accordance with OECD TG 439. The LbL-3D Skin SIT validation study was performed by three participating laboratories and consisted of three independent tests using 20 reference chemicals. The results obtained with the LbL-3D Skin demonstrated high within-laboratory and between-laboratory reproducibility, as well as high accuracy for use as a stand-alone assay to distinguish skin irritants from nonirritants. The predictive potency of LbL-3D Skin SIT using total 54 test chemicals were comparable to those in other RhE models in OECD TG 439. The validation study demonstrated that LbL-3D Skin has proven to be a robust and reliable method for predicting skin irritation.

Preparation and Characterization of Thermoresponsive Poly(N-vinylisobutyramide) Microgels.

Microgels are soft, adaptive materials exhibiting various properties not only like hydrogels and microparticles but also like macromolecules, colloids, and surfactants. To widen the range of their biomedical and environmental applications, the exploration of an alternative for poly(N-alkylacrylamide)s without potential safety risks is of great importance. In this article, thermoresponsive poly(N-vinylisobutyramide) (PNVIBA) microgels of uniform size were synthesized with NVIBA as a monomer and N,N'-5-oxanonamethyene-bis-N-vinylacetamide as a cross-linker in the presence of sodium dodecyl sulfate by aqueous free radical precipitation polymerization. The introduction of cationic groups into PNVIBA microgels was also accomplished using N-vinylformamide (NVF) as a comonomer and the subsequent conversion of NVF into vinylamine by hydrolysis.

Efficient Softening and Toughening Strategies of Cellulose Nanofibril Nanocomposites Using Comb Polyurethane.

Cellulose nanofibrils (CNFs) have attracted attention as building blocks for sustainable materials owing to their high performance and the advantages of their abundant natural resources. Bioinspired CNF/polymer nanocomposites, consisting of a soft polymer phase and a high fraction (>50 wt %) of CNF reinforcement, have been focused on excellent mechanical properties, including Young's modulus, mechanical strength, and toughness, mimicking the energy dissipation system in nature. However, efficient softening and toughening with a small amount of the soft phase is still a challenge because a large amount of the polymer phase (nearly 50%) is still required to provide ductility and toughness. Here, we describe a topological strategy in the polymer phase for efficient toughening of bioinspired CNF nanocomposites with a water-soluble comb polyurethane (PU). The comb PU provided higher elongation at break and more efficient flexibility for the nanocomposite than the linear PU, even at a small content. Moreover, CNF nanocomposites with 30 wt % of PU content and tetrabutylammonium as bulky counterions showed enhanced toughness (180% higher) and strain at break (250% higher) when compared to pure CNF due to the promotion of slippage between nanofibrils. Scanning electron microscopy (SEM) images of the fracture surface for CNF/comb PU nanocomposites displayed the pull-out of mesoscale layers and nanofibrils, supporting that the comb topology promotes the slippage between fibrils. Furthermore, the rheological study revealed that the comb PU has an entanglement plateau modulus lower than linear PU by 1 order of magnitude, related to the loosened entanglements. Our study establishes an efficient softening and toughening strategy while using small amounts of polymer phase addition, promoting interfibrillar slippage with the loosely entangled comb PU phase.

Preparation of stereocomplex and pseudo-polyrotaxane with various cyclodextrins as wheel components using triblock copolymer of poly(ethylene glycol) and polylactide.

The ABA-type triblock-copolymers (BCPs) of polylactide (PLA) and poly(ethylene glycol) (PEG) were synthesized as axle components for rotaxane formation. It is known that α-cyclodextrin (CD) exists near the PEG moiety in pseudo-polyrotaxane (PPRX), and the PLA moiety can form a stereocomplex (SC), by mixing with L- and D-isomers. In this study, various CDs, including ß-CD and γ-CD, were used as wheel components, and effects of CD structures on both PPRX and SC formations were studied. The solubility of CDs is influenced to form the PPRX, resulting in differing numbers of CDs in the axle. PPRX structures were investigated by 1H NMR, NOESY, and DOSY, and SC structures were investigated by FT-IR and XRD. Their thermal properties were also evaluated by DSC and TGA, to consider the physical properties of the simultaneous formation of PPRX and SC. This study gave insight into the complicated host-guest and polymer-polymer interactions.

One-Shot Preparation of Thermoresponsive Comb Polyurethane Hydrogel for Both Excellent Toughness and Large Volume Switching.

Thermoresponsive degradable polyurethane (PU) hydrogels are expected as the next-generation biomedical devices, although they have an important trade-off relationship between toughness and thermoresponsive properties. Tough and thermoresponsive comb PU hydrogels are prepared by one-shot poly-addition between hexamethylene diisocyanate, triethylene glycol tartrate ester, poly(ethylene glycol) 300 (PEG300), and glycerol. The swelling ratio change between 4 and 40 °C decreases as the proportion of PEG300 increases and is maintained at 600% switching within 30% PEG300. Moreover, the one-shot preparation of comb PU hydrogel with PEG300 improves toughness up to 100 times compared to the original comb PU hydrogel. Rheological analysis suggests that the bimodal toughening phenomenon for the proportion of PEG300 is due to the network structure and the hydrophobic aggregation domain. This simple toughening method using a heteronetwork based on the kinetic difference of step-growth PU is expected to apply to other chemical structures.

Thermoresponsive Polyurethane Bearing Oligo(Ethylene Glycol) as Side Chain Without Polyol at Polymer Backbone Achieved Excellent Hydrophilic and Hydrophobic Switching.

In order to prepare thermoresponsive polyurethane gels, a novel polyurethane bearing oligo(ethylene glycol) (OEG) as the side chain is successfully synthesized with hexamethylene diisocyanate and OEG tartrate ester. The aqueous solution of the polyurethane shows sharp and clear lower critical solution temperature behavior at 34 °C. Furthermore, a hydrogel based on the same polyurethane is also successfully prepared using glycerol as the crosslinker. This polyurethane hydrogel including 10 mol% of glycerol presents a large swelling ratio change between 4 °C and 37 °C from 250% to 40%.

Thermal Treatment of Poly (N-vinylformamide) Produced Hydrogels Without the Use of Chemical Crosslinkers.

Hydrogel preparations using poly(N-vinylformamide) (PNVF) and poly(N-vinylacetamide) (PNVA), which are composed of non-conjugated vinyl monomers, N-vinylformamide (NVF) and N-vinylacetamide (NVA), were investigated without chemical crosslinkers. Hydrogen bonding interaction between the polymers and poly(ethylene glycol) have been firstly attempted to result in unstable film, which is easily soluble in water. On the other hand, the simple thermal treatment of the PNVF films at 200 °C for several hours produced the hydrogels after water immersion, although PNVA did not produce any hydrogels under the same condition. The swelling ratios of the formed hydrogel ranged from 100 to 250. The analysis of the supernatant reveals the structural change at alpha proton of PNVF. Furthermore, the decrease of molecular weights were observed by SEC analysis when the hydrogels formed. The possible mechanism of the crosslinking reaction is also discussed. The present study provides the novel method to prepare PNVF hydrogels without the use of chemical crosslinkers.

Force Estimation on the Contact of Poly(l,l-lactide) and Poly(d,d-lactide) Surfaces Regarding Stereocomplex Formation.

The stereocomplex formation of poly(l,l-lactide) (PLLA) and poly(d,d-lactide) (PDLA) was selected in order to investigate the interaction of the two surfaces including hydrogen bonding and van der Waals interaction. Adhesion force measurement using surface force apparatus (SFA) equipped with an optical microscope was conducted on the PLLA and PDLA spin-coated films. The adhesion forces, Fad, phenomenologically followed the linear relation with the applied normal load, L. For the force Fad between PLLA and PDLA films with low molecular weights (PLLA, Mn = 2800; PDLA, : Mn = 2100), the slope of linear fitting of Fad vs L was significantly larger for the heterointerface (PLLA/PLDA) compared with that for the homointerface (PLLA/PLLA and PDLA/PDLA). However, when polymers with higher molecular weights (PLLA, Mn = 8500; PDLA, Mn = 8300) were measured, the slopes of linear fitting lines were almost the same for hetero- and homointerfaces. This indicated that the mobility of the lower molecular weight PLLA/PDLA films promoted the selective interaction of PLLA and PDLA under the applied normal loads. The adhesion between the outermost PLLA layer and PDLA layer prepared by layer-by-layer (LbL) assembly was also measured. It is interesting that the adhesion force was very weak in this case. This weak adhesion could be explained by the much less mobility of the polymer chain due to the stereocomplex formation within the LbL layers. This study demonstrated that the adhesion force due to the selective interaction of PLLA and PDLA between PLLA/PDLA films could be directly measured, and depended on the mobility of the outermost polymer chains, which reflected the different structures of polymer chains in the organized complex films.

Hydrogen-Bonded Multilayer Films Based on Poly(N-vinylamide) Derivatives and Tannic Acid.

Layer-by-layer (LbL) assembly based on hydrogen-bonding interactions is generating great interest for biomedical applications because it is composed of neutral polymers, while LbL assembly based on electrostatic interaction requires polycations which may induce toxicity issues. As a neutral polymer, poly(N-vinylamide), which has low toxicity compared to poly(acrylamide), has the potential to fabricate LbL thin films via hydrogen-bonding interactions. Herein we report interpolymer complexes of poly(N-vinylamide)s and natural polyphenol tannic acid to form the multilayered thin film. Poly(N-vinylformamide) and poly(N-vinylacetamide), which are water-soluble and insoluble in acetonitrile, could not form complexes with TA in water. On the other hand, N-alkylated poly(N-vinylamide) such as poly(N-ethyl-N-vinylformamide) and poly(N-methyl-N-vinylacetamide) was soluble in acetonitrile and allowed the LbL assembly to proceed with TA. Furthermore, the QCM frequency shift with films composed of poly(N-ethyl-N-vinylformamide) and TA were stable in water, while those of poly(N-methyl-N-vinylacetamide) and TA were instable in water, possibly because formamide has lower steric hindrance compared to acetamide to allow stronger hydrogen-bonding interactions to take place. Thus, LbL assembly reactions with alkylated poly(N-vinylamide)s and TA were investigated and revealed that poly(N-ethyl-N-formamide) and TA, which are water-soluble, effectively interacted with one another to generate water-stable hydrogen-bonded multilayered films.

Stereocomplex Film Using Triblock Copolymers of Polylactide and Poly(ethylene glycol) Retain Paxlitaxel on Substrates by an Aqueous Inkjet System.

The stereocomplex formation of poly(L,L-lactide) (PLLA) and poly(D,D-lactide) (PDLA) using an inkjet system was expanded to the amphiphilic copolymers, using poly(ethylene glycol) (PEG) as a hydrophilic polymer. The diblock copolymers, which are composed of PEG and PLLA (MPEG-co-PLLA) and PEG and PDLA (MPEG-co-PDLA), were employed for thin-film preparation using an aqueous inkjet system. The solvent and temperature conditions were optimized for the stereocomplex formation between MPEG-co-PLLA and MPEG-co- PDLA. As a result, the stereocomplex was adequately formed in acetonitrile/water (1:1, v/v) at 40 °C. The aqueous conditions improved the stereocomplex film preparation, which have suffered from clogging when using the organic solvents in previous work. The triblock copolymers, PLLA-co-PEG-co-PLLA and PDLA-co-PEG-co-PDLA, were employed for square patterning with the inkjet system, which produced thin films. The amphiphilic polymer film was able to retain hydrophobic compounds inside. The present result contributed to the rapid film preparation by inkjet, retaining drugs with difficult solubility in water, such as paclitaxel within the films.

Sustainable Coating Materials: Exploring the Influence of Adjuvants on Kaolinite Suspension with Insights from Five Local Mining Clays.

Herein, we presented a comprehensive case study on the kaolin suspension derived from mining powder, with a specific emphasis on its mineral constituents within the size range of 2-5 µm and its suitability in spray applications. We have systematically investigated the influence of adjuvants, existing in both organic molecules and polymers, on the sedimentation behavior of clay suspensions. The investigations included the analysis of turbidity, dispersion weight, pH, and surface charge as key parameters. Our findings revealed that the specific presence of PEG-PPG-PEG, PAA, and PSAMA had a notable effect on delaying the suspension of sedimentation by the actual sediment weight as well as enhancing the uniformity of clay coating by the reflection efficiency of coating materials in PPFD units. To enhance sustainability in coating materials, it was essential to elucidate the optimal amounts of adjuvants and the pH levels as they are closely related to the efficacy of tree-coated spraying and soil conditions.

Improved Gas Hydrate Kinetic Inhibition for 5-Methyl-3-vinyl-2-oxazolidinone Copolymers and Synergists.

Kinetic hydrate inhibitors (KHIs) are used to prevent deposits and plugging of oil and gas production flow lines by gas hydrates. The key ingredient in a KHI formulation is a water-soluble amphiphilic polymer. Recently, polymers of a new commercially available 5-ring vinylic monomer 5-methyl-3-vinyl-2-oxazolidinone (VMOX) were investigated as KHIs and shown to perform better than some commercial KHI polymers such as poly(N-vinyl pyrrolidone). This initial study using slow constant cooling (SCC) in rocking cells with a synthetic natural gas has now been expanded to further explore low molecular weight PVMOX homopolymers and VMOX copolymers as well as blends with nonpolymeric synergists. A PVMOX homopolymer with improved KHI performance was found using 3-mercaptoacetic acid as a chain transfer agent in the radical polymerization of VMOX. Among a range of copolymers, VMOX:n-butyl acrylate copolymers in particular gave good KHI performance, better than the PVMOX homopolymer. Among the potential synergists, trialkylamine oxides (alkyl = n-butyl or iso-pentyl) and tetra(n-pentyl)ammonium bromide to 2500 ppm were found to be antagonistic with PVMOX at the test concentrations while some alcohols and glycols were synergetic. The best synergist was 2,4,7,9-tetramethyl-5-decyne-4,7-diol (TMDD). For example, a mixture of 2500 ppm TMDD with 2500 ppm PVMOX (Mw 2400 g/mol) performed significantly better than 5000 ppm PVMOX. Addition of 1250 ppm TMDD to 2500 ppm VMOX:n-butyl acrylate 6:4 copolymer lowered the hydrate onset temperature in SCC tests by a further 3 °C compared to the copolymer alone giving hydrate onset at 4.2 °C.

Chemometrics Approach Based on Wavelet Transforms for the Estimation of Monomer Concentrations from FTIR Spectra.

Fourier-transform infrared (FTIR) spectroscopy can detect the presence of functional groups and molecules directly from a mixed solution of organic molecules. Although it is quite useful to monitor chemical reactions, quantitative analysis of FTIR spectra becomes difficult when various peaks of different widths overlap. To overcome this difficulty, we propose a chemometrics approach to accurately predict the concentration of components in chemical reactions, yet interpretable by humans. The proposed method first decomposes a spectrum into peaks with various widths by the wavelet transform. Subsequently, a sparse linear regression model is built using the wavelet coefficients. Models by the method are interpretable using the regression coefficients shown on Gaussian distributions with various widths. The interpretation is expected to reveal the relation of broad regions in spectra to the model prediction. In this study, we conducted the prediction of monomer concentration in copolymerization reactions of five monomers against methyl methacrylate by various chemometric approaches including conventional methods. A rigorous validation scheme revealed that the proposed method overall showed better predictive ability than various linear and non-linear regression methods. The visualization results were consistent with the interpretation obtained by another chemometric approach and qualitative evaluation. The proposed method is found to be useful for calculating the concentrations of monomers in copolymerization reactions and for the interpretation of spectra.

Layer-by-layer assembly of partially sulfonated isotactic polystyrene with poly(vinylamine).

The stereoregular synthetic polymer isotactic polystyrene bearing partially sulfonated groups (SiPS) was used as a layer-by-layer assembled thin film for the first time. When a low molecular weight compound was employed as the pair for the alternative layer-by-layer (LbL) assembly, the frequency shift was very small using quartz crystal microbalance (QCM) analysis, whereas poly(vinylamine) (PVAm) formed an effective pair for the construction of LbL films with SiPS. When it was neutralized, SiPS was not assembled, probably due to the loss of effective polymer-polymer interactions. The ionic strength conditions revealed a slight difference of the assembly behavior on the isotactic polymer as compared to the atactic one. The assembled LbL film showed the same peaks over the range from 1141 to 1227 cm(-1) and 700 cm(-1) in the FT-IR/ATR spectra as the bulk complex of SiPS/PVAm, and the thickness on one side was calculated at 76 nm by QCM analysis. The surface roughness of the film was also observed by AFM.

Bioactivity of star-shaped polycaprolactone/chitosan composite hydrogels for biomaterials.

Recently, our group reported the synthesis and fabrication of composite hydrogels of chitosan (CS) and star-shaped polycaprolactone (stPCL). The co-crosslink of modified stPCL with carboxyl at the end chain (stPCL-COOH) provided good mechanical properties and stability to the composite hydrogels. This research presents the bioactivities of composite hydrogels showing a potential candidate to develop biomaterials such as wound dressing and bone tissue engineering. The bioactivities were the antibacterial activity, cell viability, skin irritation, decomposability, and ability to attach ions for apatite nucleation. The results showed that all the composite hydrogels were completely decomposed within 2 days. The composite hydrogels had better antibacterial activity and higher efficiency to Gram-negative (Escherichia coli) than to Gram-positive (Staphylococcus epidermidis) bacteria. The composite hydrogels were studied for cell viability based on MTT assay and skin irritation on rabbit skin. The results indicated high cell survival more than 80% and no skin irritation. In addition, the results showed that calcium and phosphorous were preferentially attached to the composite hydrogel surface to grow apatite crystal (Ca/P ratio 1.86) compared to attaching to the chitosan hydrogel (Ca/P ratio 1.48) in 21 days of testing.

Oxyvinylenelactam Polymers-A New Class of Lactam-Based Kinetic Hydrate Inhibitor Polymers.

The deployment of kinetic hydrate inhibitors (KHIs) is a chemical method for the prevention of gas hydrate plugging in gas, condensate, and oil production flow lines. Polymers made using the monomer N-vinylcaprolactam (VCap) are one of the most common KHI classes. Alternative classes of polymers containing caprolactam groups are rare. Here, we present a study on oxyvinylenelactam polymers and copolymers with pendant piperidone or caprolactam groups. Low-molecular-weight homo- and copolymers were obtained. The nonrotating vinylene groups impart rigidity to the polymer backbone. Poly(oxyvinylenecaprolactam) (POVCap) was insoluble in water, but poly(oxyvinylenepiperidone) (POVPip) and OVPip:OVCap copolymers with 60+ mol % OVPip were soluble with low cloud points. KHI screening tests were carried out using the slow constant cooling method in steel rocking cells. POVPip was water soluble with no cloud point up to 95 °C but showed a poor KHI performance. In contrast, OVPip:OVCap copolymers with about 60-70 mol % OVPip were also water soluble and showed a reasonable KHI performance, better than that of poly(N-vinylpyrrolidone) but not as good as that of poly(N-vinylcaprolactam). Surprisingly, several additives known to be good synergists for VCap-based polymers showed negligible synergy or were antagonistic with the 62:38 OVPip:OVCap copolymer with regard to lowering the onset temperature of hydrate formation. However, a blend with hexabutylguanidinium chloride showed a strong effect to delay the onset of rapid hydrate formation.

Fusion of porous isotactic poly(methyl methacrylate) thin films fabricated on silica nanoparticles with stepwise stereocomplex assembly.

Structures of silica nanoparticles coated with stereocomplex thin films composed of isotactic (it) poly(methyl methacrylate) (PMMA) and syndiotactic (st) poly(methacrylic acid) (PMAA) and with porous it-PMMA thin films under gentle stirring or static conditions were analyzed by dynamic light scattering (DLS) and scanning electron microscopy (SEM), respectively. The porous it-PMMA films were fabricated by stepwise stereocomplex assembling of it-PMMA and st-PMAA, and subsequent extraction of the st-PMAA from the films. From DLS results, an evident difference was not observed between the it-PMMA films and the stereocomplex films, whereas the it-PMMA films after 10 h of stirring in acetonitrile/water (4/6, v/v) and drying on a SEM stage fused to form nanostructured networks. The fusion of the it-PMMA films on the silica nanoparticles occurred not by the dissolution of it-PMMA in the mixed solvent, but rather by an interaction of the it-PMMA chains driven by the slight solvation of acetonitrile without dissolution. Thus, leaving the solution at rest would be important for film fusion on the particles, and multiple spherical substrates could promote the crosslinking of the it-PMMA chains on the particles.