Polymers

Research

14 pages, 2675 KiB

Open AccessArticle

Preparation of Water-soluble Polyion Complex (PIC) Micelles Covered with Amphoteric Random Copolymer Shells with Pendant Sulfonate and Quaternary Amino Groups

by Rina Nakahata and Shin-ichi Yusa

Polymers 2018, 10(2), 205; https://doi.org/10.3390/polym10020205 - 19 Feb 2018

Cited by 14 | Viewed by 6572

Abstract

An amphoteric random copolymer (P(SA)₉₁) composed of anionic sodium 2-acrylamido-2-methylpropanesulfonate (AMPS, S) and cationic 3-acrylamidopropyl trimethylammonium chloride (APTAC, A) was prepared via reversible addition-fragmentation chain transfer (RAFT) radical polymerization. The subscripts in the abbreviations indicate the degree of polymerization (DP). Furthermore, [...] Read more.

An amphoteric random copolymer (P(SA)₉₁) composed of anionic sodium 2-acrylamido-2-methylpropanesulfonate (AMPS, S) and cationic 3-acrylamidopropyl trimethylammonium chloride (APTAC, A) was prepared via reversible addition-fragmentation chain transfer (RAFT) radical polymerization. The subscripts in the abbreviations indicate the degree of polymerization (DP). Furthermore, AMPS and APTAC were polymerized using a P(SA)₉₁ macro-chain transfer agent to prepare an anionic diblock copolymer (P(SA)₉₁S₆₇) and a cationic diblock copolymer (P(SA)₉₁A₈₈), respectively. The DP was estimated from quantitative 13C NMR measurements. A stoichiometrically charge neutralized mixture of the aqueous P(SA)₉₁S₆₇ and P(SA)₉₁A₈₈ formed water-soluble polyion complex (PIC) micelles comprising PIC cores and amphoteric random copolymer shells. The PIC micelles were in a dynamic equilibrium state between PIC micelles and charge neutralized small aggregates composed of a P(SA)₉₁S₆₇/P(SA)₉₁A₈₈ pair. Interactions between PIC micelles and fetal bovine serum (FBS) in phosphate buffered saline (PBS) were evaluated by changing the hydrodynamic radius (R_h) and light scattering intensity (LSI). Increases in R_h and LSI were not observed for the mixture of PIC micelles and FBS in PBS for one day. This observation suggests that there is no interaction between PIC micelles and proteins, because the PIC micelle surfaces were covered with amphoteric random copolymer shells. However, with increasing time, the diblock copolymer chains that were dissociated from PIC micelles interacted with proteins. Full article

(This article belongs to the Special Issue Polymer Micelles)

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9 pages, 1793 KiB

Open AccessArticle

Elucidation of Spatial Distribution of Hydrophobic Aromatic Compounds Encapsulated in Polymer Micelles by Anomalous Small-Angle X-ray Scattering

by Shota Sasaki, Ginpei Machida, Ryosuke Nakanishi, Masaki Kinoshita and Isamu Akiba

Polymers 2018, 10(2), 180; https://doi.org/10.3390/polym10020180 - 12 Feb 2018

Cited by 6 | Viewed by 4259

Abstract

Spatial distribution of bromobenzene (BrBz) and 4-bromophenol (BrPh) as hydrophobic aromatic compounds incorporated in polymer micelles with vesicular structure consisting of poly(ethylene glycol)-b-poly(tert-butyl methacrylate) (PEG-b-PtBMA) in aqueous solution is investigated by anomalous small-angle X-ray scattering (ASAXS) analyses [...] Read more.

Spatial distribution of bromobenzene (BrBz) and 4-bromophenol (BrPh) as hydrophobic aromatic compounds incorporated in polymer micelles with vesicular structure consisting of poly(ethylene glycol)-b-poly(tert-butyl methacrylate) (PEG-b-PtBMA) in aqueous solution is investigated by anomalous small-angle X-ray scattering (ASAXS) analyses near Br K edge. Small-angle X-ray scattering (SAXS) intensities from PEG-b-PtBMA micelles containing BrBz and BrPh were decreased as the energy of incident X-ray approached to Br K edge corresponding to the energy dependence of anomalous scattering factor of Br. The analysis for the energy dependence of SAXS profiles from the PEG-b-PtBMA micelles containing BrBz revealed that BrBz molecules were located in hydrophobic layer of PEG-b-PtBMA micelles. On the contrary, it was found by ASAXS that BrPh existed not only in the hydrophobic layer but also in the shell layer. Since ASAXS analysis successfully accomplished to visualize the spatial distribution of hydrophobic molecules in polymer micelles, it should be expected to be a powerful tool for characterization of drug delivery vehicles. Full article

(This article belongs to the Special Issue Polymer Micelles)

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17 pages, 4515 KiB

Open AccessArticle

Synergistic Effect of Binary Mixed-Pluronic Systems on Temperature Dependent Self-assembly Process and Drug Solubility

by Chin-Fen Lee, Hsueh-Wen Tseng, Pratap Bahadur and Li-Jen Chen

Polymers 2018, 10(1), 105; https://doi.org/10.3390/polym10010105 - 22 Jan 2018

Cited by 23 | Viewed by 6263

Abstract

Mixed Pluronic micelles from very hydrophobic and very hydrophilic copolymers were selected to scrutinize the synergistic effect on the self-assembly process as well as the solubilization capacity of ibuprofen. The tendency of mixing behavior between parent copolymers was systematically examined from two perspectives: [...] Read more.

Mixed Pluronic micelles from very hydrophobic and very hydrophilic copolymers were selected to scrutinize the synergistic effect on the self-assembly process as well as the solubilization capacity of ibuprofen. The tendency of mixing behavior between parent copolymers was systematically examined from two perspectives: different block chain lengths at same hydrophilicity (L92 + F108, +F98, +F88, and +F68), as well as various hydrophobicities at the same PPO moiety (L92 + F88, +F87, and +P84). Temperature-dependent micellization in these binary systems was clearly inspected by the combined use of high sensitivity differential scanning calorimeter (HSDSC) and dynamic light scattering (DLS). Changes in heat capacity and size of aggregates at different temperatures during the whole micellization process were simultaneously observed and examined. While distinction of block chain length between parent copolymers increases, the monodispersity of the binary Pluronic systems decreases. However, parent copolymers with distinct PPO moieties do not affirmatively lead to non-cooperative binding, such as the L92 + P84 system. The addition of ibuprofen promotes micellization as well as stabilizes aggregates in the solution. The partial replacement of the hydrophilic Pluronic by a more hydrophobic Pluronic L92 would increase the total hydrophobicity of mixed Pluronics used in the system to substantially enhance the solubility of ibuprofen. The solubility of ibuprofen in the 0.5 wt % L92 + 0.368 wt % P84 system is as high as 4.29 mg/mL, which is 1.4 times more than that of the 0.868 wt % P84 system and 147 times more than that in pure water at 37 °C. Full article

(This article belongs to the Special Issue Polymer Micelles)

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11 pages, 1714 KiB

Open AccessFeature PaperArticle

Aggregation of Cationic Amphiphilic Block and Random Copoly(vinyl ether)s with Antimicrobial Activity

by Yukari Oda, Kazuma Yasuhara, Shokyoku Kanaoka, Takahiro Sato, Sadahito Aoshima and Kenichi Kuroda

Polymers 2018, 10(1), 93; https://doi.org/10.3390/polym10010093 - 19 Jan 2018

Cited by 12 | Viewed by 5837

Abstract

In this study, we investigated the aggregation behaviors of amphiphilic poly(vinyl ether)s with antimicrobial activity. We synthesized a di-block poly(vinyl ether), B38₂₆, composed of cationic primary amine and hydrophobic isobutyl (iBu) side chains, which previously showed antimicrobial activity against [...] Read more.

In this study, we investigated the aggregation behaviors of amphiphilic poly(vinyl ether)s with antimicrobial activity. We synthesized a di-block poly(vinyl ether), B38₂₆, composed of cationic primary amine and hydrophobic isobutyl (iBu) side chains, which previously showed antimicrobial activity against Escherichia coli. B38₂₆ showed similar uptake behaviors as those for a hydrophobic fluorescent dye, 1,6-diphenyl-1,3,5-hexatriene, to counterpart polymers including homopolymer H44 and random copolymer R40₂₅, indicating that the iBu block does not form strong hydrophobic domains. The cryo-TEM observations also indicated that the polymer aggregate of B38₂₆ appears to have low-density polymer chains without any defined microscopic structures. We speculate that B38₂₆ formed large aggregates by liquid-liquid separation due to the weak association of polymer chains. The fluorescence microscopy images showed that B38₂₆ bonds to E. coli cell surfaces, and these bacterial cells were stained by propidium iodide, indicating that the cell membranes were significantly damaged. The results suggest that block copolymers may provide a new platform to design and develop antimicrobial materials that can utilize assembled structures and properties. Full article

(This article belongs to the Special Issue Polymer Micelles)

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18 pages, 8877 KiB

Open AccessArticle

A Comparative Study on Micellar and Solubilizing Behavior of Three EO-PO Based Star Block Copolymers Varying in Hydrophobicity and Their Application for the In Vitro Release of Anticancer Drugs

by Bijal Vyas, Sadafara A. Pillai, Anita Bahadur and Pratap Bahadur

Polymers 2018, 10(1), 76; https://doi.org/10.3390/polym10010076 - 15 Jan 2018

Cited by 21 | Viewed by 6443

Abstract

The temperature and pH dependent self-assembly of three star shaped ethylene oxide-propylene oxide (EO-PO) block copolymers (Tetronics^® 304, 904 and 908) with widely different hydrophobicity was examined in aqueous solutions. Physico-chemical methods viz. viscosity, cloud point, solubilization along with thermal, scattering and [...] Read more.

The temperature and pH dependent self-assembly of three star shaped ethylene oxide-propylene oxide (EO-PO) block copolymers (Tetronics^® 304, 904 and 908) with widely different hydrophobicity was examined in aqueous solutions. Physico-chemical methods viz. viscosity, cloud point, solubilization along with thermal, scattering and spectral techniques shows strongly temperature and salt dependent solution behavior. T304 possessing low molecular weight did not form micelles; moderately hydrophilic T904 remained as micelles at ambient temperature and showed micellar growth while very hydrophilic T908 formed micelles at elevated temperatures. The surface activity/micellization/solubilization power was favored in the presence of salt. The copolymers turn more hydrophilic in acidic pH due to protonation of central ethylene diamine moiety that hinders micelle formation. The solubilization of a model insoluble azo dye 1-(o-Tolylazo)-2-naphthol (Orange OT) and hydrophobic drugs (quercetin and curcumin) for copolymer solutions in aqueous and salt solutions are also reported. Among the three copolymers, T904 showed maximum solubility of dye and drugs, hence the in vitro release of drugs from T904 micelles was estimated and the effect on cytotoxicity of loading the drugs in T904 micelles was compared with the cytotoxicity of free drugs on the CHO-K1 cells. The results from the present work provide a better insight in selection of Tetronics^® for their application in different therapeutic applications. Full article

(This article belongs to the Special Issue Polymer Micelles)

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13 pages, 1554 KiB

Open AccessArticle

Theory of the Flower Micelle Formation of Amphiphilic Random and Periodic Copolymers in Solution

by Takahiro Sato

Polymers 2018, 10(1), 73; https://doi.org/10.3390/polym10010073 - 14 Jan 2018

Cited by 8 | Viewed by 6469

Abstract

The mixing Gibbs energy Δg_m for the flower-micelle phase of amphiphilic random and periodic (including alternating) copolymers was formulated on the basis of the lattice model. The formulated Δg_m predicts (1) the inverse proportionality of the aggregation number to [...] Read more.

The mixing Gibbs energy Δg_m for the flower-micelle phase of amphiphilic random and periodic (including alternating) copolymers was formulated on the basis of the lattice model. The formulated Δg_m predicts (1) the inverse proportionality of the aggregation number to the degree of polymerization of the copolymer, (2) the increase of the critical micelle concentration with decreasing the hydrophobe content, and (3) the crossover from the micellization to the liquid–liquid phase separation as the hydrophobe content increases. The transition from the uni-core flower micelle to the multi-core flower necklace as the degree of polymerization increases was also implicitly indicated by the theory. These theoretical results were compared with experimental results for amphiphilic random and alternating copolymers reported so far. Full article

(This article belongs to the Special Issue Polymer Micelles)

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3383 KiB

Open AccessFeature PaperArticle

Micellization Thermodynamics of Pluronic P123 (EO₂₀PO₇₀EO₂₀) Amphiphilic Block Copolymer in Aqueous Ethylammonium Nitrate (EAN) Solutions

by Zhiqi He and Paschalis Alexandridis

Polymers 2018, 10(1), 32; https://doi.org/10.3390/polym10010032 - 28 Dec 2017

Cited by 64 | Viewed by 13067

Abstract

Poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymers (commercially available as Pluronics or Poloxamers) can self-assemble into various nanostructures in water and its mixtures with polar organic solvents. Ethylammonium nitrate (EAN) is a well-known protic ionic liquid that is expected to affect amphiphile self-assembly [...] Read more.

Poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymers (commercially available as Pluronics or Poloxamers) can self-assemble into various nanostructures in water and its mixtures with polar organic solvents. Ethylammonium nitrate (EAN) is a well-known protic ionic liquid that is expected to affect amphiphile self-assembly due to its ionic nature and hydrogen bonding ability. By proper design of isothermal titration calorimetry (ITC) experiments, we determined the enthalpy and other thermodynamic parameters of Pluronic P123 (EO₂₀PO₇₀EO₂₀) micellization in aqueous solution at varied EAN concentration. Addition of EAN promoted micellization in a manner similar to increasing temperature, e.g., the addition of 1.75 M EAN lowered the critical micelle concentration (CMC) to the same extent as a temperature increase from 20 to 24 °C. The presence of EAN disrupts the water solvation around the PEO-PPO-PEO molecules through electrostatic interactions and hydrogen bonding, which dehydrate PEO and promote micellization. At EAN concentrations lower than 1 M, the PEO-PPO-PEO micellization enthalpy and entropy increase with EAN concentration, while both decrease above 1 M EAN. Such a change can be attributed to the formation by EAN of semi-ordered nano-domains with water at higher EAN concentrations. Pyrene fluorescence suggests that the polarity of the mixed solvent decreased linearly with EAN addition, whereas the polarity of the micelle core remained unaltered. This work contributes to assessing intermolecular interactions in ionic liquid + polymer solutions, which are relevant to a number of applications, e.g., drug delivery, membrane separations, polymer electrolytes, biomass processing and nanomaterial synthesis. Full article

(This article belongs to the Special Issue Polymer Micelles)

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5356 KiB

Open AccessArticle

PLMA-b-POEGMA Amphiphilic Block Copolymers as Nanocarriers for the Encapsulation of Magnetic Nanoparticles and Indomethacin

by Athanasios Skandalis, Andreas Sergides, Aristides Bakandritsos and Stergios Pispas

Polymers 2018, 10(1), 14; https://doi.org/10.3390/polym10010014 - 23 Dec 2017

Cited by 11 | Viewed by 5962

Abstract

We report here on the utilization of poly(lauryl methacrylate)-b-poly(oligo ethylene glycol methacrylate) (PLMA-b-POEGMA) amphiphilic block copolymers, which form compound micelles in aqueous solutions, as nanocarriers for the encapsulation of either magnetic iron oxide nanoparticles or iron oxide nanoparticles, and [...] Read more.

We report here on the utilization of poly(lauryl methacrylate)-b-poly(oligo ethylene glycol methacrylate) (PLMA-b-POEGMA) amphiphilic block copolymers, which form compound micelles in aqueous solutions, as nanocarriers for the encapsulation of either magnetic iron oxide nanoparticles or iron oxide nanoparticles, and the model hydrophobic drug indomethacin in the their hydrophobic core. The mixed nanostructures were characterized using dynamic light scattering (DLS) and transmission electron microscopy (TEM) in terms of their structure and solution properties. Magnetophoresis experiments showed that the mixed solutions maintain the magnetic properties of the initial iron oxide nanoparticles. Results indicate that the cumulative hydrophilic/hydrophobic balance of all components determines the colloidal stability of the nanosystems. The effect of salt and bovine serum albumin (BSA) protein concentration on the structure of the mixed nanostructures was also investigated. Disintegration of the mixed nanostructures was observed in both cases, showing the importance of these parameters in the structure formation and stability of such complex mixed nanosystems. Full article

(This article belongs to the Special Issue Polymer Micelles)

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3703 KiB

Open AccessFeature PaperArticle

Photo Irradiation-Induced Core Crosslinked Poly(ethylene glycol)-block-poly(aspartic acid) Micelles: Optimization of Block Copolymer Synthesis and Characterization of Core Crosslinked Micelles

by Kouichi Shiraishi, Shin-ichi Yusa, Masanori Ito, Keita Nakai and Masayuki Yokoyama

Polymers 2017, 9(12), 710; https://doi.org/10.3390/polym9120710 - 14 Dec 2017

Cited by 4 | Viewed by 4879

Abstract

We used photo irradiation to design core crosslinked polymeric micelles whose only significant physico-chemical change was in their physico-chemical stability, which helps elucidate poly(ethylene glycol) (PEG)-related immunogenicity. Synthetic routes and compositions of PEG-b-poly(aspartic acid) block copolymers were optimized with the control [...] Read more.

We used photo irradiation to design core crosslinked polymeric micelles whose only significant physico-chemical change was in their physico-chemical stability, which helps elucidate poly(ethylene glycol) (PEG)-related immunogenicity. Synthetic routes and compositions of PEG-b-poly(aspartic acid) block copolymers were optimized with the control of n-alkyl chain length and photo-sensitive chalcone moieties. The conjugation ratio between n-alkyl chain and the chalcone moieties was controlled, and upon the mild photo irradiation of polymeric micelles, permanent crosslink proceeded in the micelle cores. In the optimized condition, the core crosslinked (CCL) micelles exhibited no dissociation while the non-CCL micelles exhibited dissociation. These results indicate that the photo-crosslinking reactions in the inner core were successful. A gel-permeation chromatography (GPC) measurement revealed a difference between the micellar-formation stability of CCL micelles and that of the non-CCL micelles. GPC experiments revealed that the CCL micelles were more stable than the non-CCL micelles. Our research also revealed that photo-crosslinking reactions did not change the core property for drug encapsulation. In conclusion, the prepared CCL micelles exhibited the same diameter, the same formula, and the same inner-core properties for drug encapsulation as did the non-CCL micelles. Moreover, the CCL micelles exhibited non-dissociable micelle formation, while the non-CCL micelles exhibited dissociation into single block copolymers. Full article

(This article belongs to the Special Issue Polymer Micelles)

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6004 KiB

Open AccessArticle

Acetal-Linked Paclitaxel Polymeric Prodrug Based on Functionalized mPEG-PCL Diblock Polymer for pH-Triggered Drug Delivery

by Yinglei Zhai, Xing Zhou, Lina Jia, Chao Ma, Ronghua Song, Yanhao Deng, Xueyao Hu and Wei Sun

Polymers 2017, 9(12), 698; https://doi.org/10.3390/polym9120698 - 11 Dec 2017

Cited by 29 | Viewed by 7185

Abstract

The differences in micro-environment between cancer cells and the normal ones offer the possibility to develop stimuli-responsive drug-delivery systems for overcoming the drawbacks in the clinical use of anticancer drugs, such as paclitaxel, doxorubicin, and etc. Hence, we developed a novel endosomal pH-sensitive [...] Read more.

The differences in micro-environment between cancer cells and the normal ones offer the possibility to develop stimuli-responsive drug-delivery systems for overcoming the drawbacks in the clinical use of anticancer drugs, such as paclitaxel, doxorubicin, and etc. Hence, we developed a novel endosomal pH-sensitive paclitaxel (PTX) prodrug micelles based on functionalized poly(ethylene glycol)-poly(ε-caprolactone) (mPEG-PCL) diblock polymer with an acid-cleavable acetal (Ace) linkage (mPEG-PCL-Ace-PTX). The mPEG-PCL-Ace-PTX₅ with a high drug content of 23.5 wt % was self-assembled in phosphate buffer (pH 7.4, 10 mM) into nanosized micelles with an average diameter of 68.5 nm. The in vitro release studies demonstrated that mPEG-PCL-Ace-PTX₅ micelles was highly pH-sensitive, in which 16.8%, 32.8%, and 48.2% of parent free PTX was released from mPEG-PCL-Ace-PTX₅ micelles in 48 h at pH 7.4, 6.0, and 5.0, respectively. Thiazolyl Blue Tetrazolium Bromide (MTT) assays suggested that the pH-sensitive PTX prodrug micelles displayed higher therapeutic efficacy against MCF-7 cells compared with free PTX. Therefore, the PTX prodrug micelles with acetal bond may offer a promising strategy for cancer therapy. Full article

(This article belongs to the Special Issue Polymer Micelles)

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3133 KiB

Open AccessArticle

Surface Active to Non-Surface Active Transition and Micellization Behaviour of Zwitterionic Amphiphilic Diblock Copolymers: Hydrophobicity and Salt Dependency

by Sivanantham Murugaboopathy and Hideki Matsuoka

Polymers 2017, 9(9), 412; https://doi.org/10.3390/polym9090412 - 5 Sep 2017

Cited by 6 | Viewed by 7136

Abstract

We have synthesized a range of zwitterionic amphiphilic diblock copolymers with the same hydrophilic block (carboxybetaine) but with different hydrophobic blocks (n-butylmethacrylate (n-BMA) or 2-ethylhexylacrylate (EHA)) by the reversible addition–fragmentation chain transfer (RAFT) polymerization method. Herein, we systematically examined [...] Read more.

We have synthesized a range of zwitterionic amphiphilic diblock copolymers with the same hydrophilic block (carboxybetaine) but with different hydrophobic blocks (n-butylmethacrylate (n-BMA) or 2-ethylhexylacrylate (EHA)) by the reversible addition–fragmentation chain transfer (RAFT) polymerization method. Herein, we systematically examined the role of hydrophobicity and salt concentration dependency of surface activity and micellization behaviour of block copolymer. Transition from surface active to non-surface active occurred with increasing hydrophobicity of the hydrophobic block of block copolymer (i.e., replacing P(n-BMA) by PEHA). Foam formation of block copolymer slightly decreased with the similar variation of the hydrophobic block of block copolymer. Block copolymer with higher hydrophobicity preferred micelle formation rather than adsorption at the air–water interface. Dynamic light scattering studies showed that block copolymer having P(n-BMA) produced near-monodisperse micelles, whereas block copolymer composed of PEHA produced polydisperse micelles. Zimm plot results revealed that the value of the second virial coefficient (A₂) changed from positive to negative when the hydrophobic block of block copolymer was changed from P(n-BMA) to PEHA. This indicates that the solubility of block copolymer having P(n-BMA) in water may be higher than that of block copolymer having PEHA in water. Unlike ionic amphiphilic block copolymer micelles, the micellar shape of zwitterionic amphiphilic block copolymer micelles is not affected by addition of salt, with a value of packing parameters of block copolymer micelles of less than 0.3. Full article

(This article belongs to the Special Issue Polymer Micelles)

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3638 KiB

Open AccessArticle

pH-Induced Association and Dissociation of Intermolecular Complexes Formed by Hydrogen Bonding between Diblock Copolymers

by Masanobu Mizusaki, Tatsuya Endo, Rina Nakahata, Yotaro Morishima and Shin-ichi Yusa

Polymers 2017, 9(8), 367; https://doi.org/10.3390/polym9080367 - 17 Aug 2017

Cited by 8 | Viewed by 5703

Abstract

Poly(sodium styrenesulfonate)–block–poly(acrylic acid) (PNaSS–b–PAA) and poly(sodium styrenesulfonate)–block–poly(N-isopropylacrylamide) (PNaSS–b–PNIPAM) were prepared via reversible addition–fragmentation chain transfer (RAFT) radical polymerization using a PNaSS-based macro-chain transfer agent. The molecular weight distributions (M_w/M [...] Read more.

Poly(sodium styrenesulfonate)–block–poly(acrylic acid) (PNaSS–b–PAA) and poly(sodium styrenesulfonate)–block–poly(N-isopropylacrylamide) (PNaSS–b–PNIPAM) were prepared via reversible addition–fragmentation chain transfer (RAFT) radical polymerization using a PNaSS-based macro-chain transfer agent. The molecular weight distributions (M_w/M_n) of PNaSS–b–PAA and PNaSS–b–PNIPAM were 1.18 and 1.39, respectively, suggesting that these polymers have controlled structures. When aqueous solutions of PNaSS–b–PAA and PNaSS–b–PNIPAM were mixed under acidic conditions, water-soluble PNaSS–b–PAA/PNaSS–b–PNIPAM complexes were formed as a result of hydrogen bonding interactions between the pendant carboxylic acids in the PAA block and the pendant amide groups in the PNIPAM block. The complex was characterized by ¹H NMR, dynamic light scattering, static light scattering, and transmission electron microscope measurements. The light scattering intensity of the complex depended on the mixing ratio of PNaSS–b–PAA and PNaSS–b–PNIPAM. When the molar ratio of the N-isopropylacrylamide (NIPAM) and acrylic acid (AA) units was near unity, the light scattering intensity reached a maximum, indicating stoichiometric complex formation. The complex dissociated at a pH higher than 4.0 because the hydrogen bonding interactions disappeared due to deprotonation of the pendant carboxylic acids in the PAA block. Full article

(This article belongs to the Special Issue Polymer Micelles)

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Review

Jump to: Research, Other

26 pages, 4367 KiB

Open AccessReview

Self-Assembly of Block and Graft Copolymers in Organic Solvents: An Overview of Recent Advances

by Leonard Ionut Atanase and Gerard Riess

Polymers 2018, 10(1), 62; https://doi.org/10.3390/polym10010062 - 11 Jan 2018

Cited by 73 | Viewed by 10564

Abstract

This review is an attempt to update the recent advances in the self-assembly of amphiphilic block and graft copolymers. Their micellization behavior is highlighted for linear AB, ABC triblock terpolymers, and graft structures in non-aqueous selective polar and non-polar solvents, including solvent mixtures [...] Read more.

This review is an attempt to update the recent advances in the self-assembly of amphiphilic block and graft copolymers. Their micellization behavior is highlighted for linear AB, ABC triblock terpolymers, and graft structures in non-aqueous selective polar and non-polar solvents, including solvent mixtures and ionic liquids. The micellar characteristics, such as particle size, aggregation number, and morphology, are examined as a function of the copolymers’ architecture and molecular characteristics. Full article

(This article belongs to the Special Issue Polymer Micelles)

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4086 KiB

Open AccessReview

Micellization of Photo-Responsive Block Copolymers

by Oliver Grimm, Felix Wendler and Felix H. Schacher

Polymers 2017, 9(9), 396; https://doi.org/10.3390/polym9090396 - 26 Aug 2017

Cited by 28 | Viewed by 10879

Abstract

This review focuses on block copolymers featuring different photo-responsive building blocks and self-assembly of such materials in different selective solvents. We have subdivided the specific examples we selected: (1) according to the wavelength at which the irradiation has to be carried out to [...] Read more.

This review focuses on block copolymers featuring different photo-responsive building blocks and self-assembly of such materials in different selective solvents. We have subdivided the specific examples we selected: (1) according to the wavelength at which the irradiation has to be carried out to achieve photo-response; and (2) according to whether irradiation with light of a suitable wavelength leads to reversible or irreversible changes in material properties (e.g., solubility, charge, or polarity). Exemplarily, an irreversible change could be the photo-cleavage of a nitrobenzyl, pyrenyl or coumarinyl ester, whereas the photo-mediated transition between spiropyran and merocyanin form as well as the isomerization of azobenzenes would represent reversible response to light. The examples presented cover applications including drug delivery (controllable release rates), controlled aggregation/disaggregation, sensing, and the preparation of photochromic hybrid materials. Full article

(This article belongs to the Special Issue Polymer Micelles)

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