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This study introduces bis(1‐cyanocyclohex‐1‐yl)trithiocarbonate (TTC‐bCCH) as a novel trithiocarbonate chain transfer agent and compares its reactivity with the previously described bis(2‐cyanopropan‐2‐yl)trithiocarbonate (TTC‐bCP) for the reversible addition‐fragmentation chain transfer (RAFT) polymerization of styrene (St), n‐butyl acrylate (nBA), and methyl methacrylate (MMA). Significant findings include the effective control of Mn and low dispersities from the onset of polymerization of St and nBA showing swift addition‐fragmentation kinetics, leading to similar behaviors between the two RAFT agents. In contrast, a fourfold decrease of the chain transfer constant to MMA is established for TTC‐bCCH over TTC‐bCP. This trend is confirmed through density functional theory (DFT) calculations. Finally, the study compares thermoplastic elastomer properties of all‐(meth)acrylic ABA block copolymers produced with both RAFT agents. The impact of dispersity of PMMA blocks on thermomechanical properties evaluated via rheological analysis reveals a more pronounced temperature dependence of the storage modulus (G′) for the triblock copolymer synthesized with TTC‐bCCH, indicating potential alteration of the phase separation. [ABSTRACT FROM AUTHOR]

Supramolecular polymer networks (SPNs) have attracted much research attention due to their good performance in the preparation of adaptive materials. Controlling the distribution of supramolecular interactions in the networks is a good strategy to tune the properties of SPNs, but corresponding study is still rare. Herein, we construct two triblock copolymers in ABA and BAB forms to control the supramolecular interaction concentrated in A block, leading to two SPNs with divergent mechanical performances. In specific, the SPN-1 formed by ABA triblock copolymer displays a slightly and densely distributed hard domain and a compact network, resulting in a decent toughness. While the SPN-2 composed of BAB triblock copolymer is rigid and less elastic, whose microphase-separated structures are more obvious, making the network difficult to withstand larger strains. These findings are conducive to deepening the understanding of SPNs and would promote the development of supramolecular block copolymers with emergent functions and applications. [ABSTRACT FROM AUTHOR]

The development of composite materials with thermo-optical properties based on smart polymeric systems and nanostructures have been extensively studied. Due to the fact of its ability to self-assemble into a structure that generates a significant change in the refractive index, one of most attractive thermo-responsive polymers is poly(N-isopropylacrylamide) (PNIPAM), as well as its derivatives such as multiblock copolymers. In this work, symmetric triblock copolymers of polyacrylamide (PAM) and PNIPAM (PAMx-b-PNIPAMy-b-PAMx) with different block lengths were prepared by reversible addition−fragmentation chain-transfer polymerization (RAFT). The ABA sequence of these triblock copolymers was obtained in only two steps using a symmetrical trithiocarbonate as a transfer agent. The copolymers were combined with gold nanoparticles (AuNPs) to prepare nanocomposite materials with tunable optical properties. The results show that copolymers behave differently in solution due to the fact of variations in their composition. Therefore, they have a different impact on the nanoparticle formation process. Likewise, as expected, an increase in the length of the PNIPAM block promotes a better thermo-optical response. [ABSTRACT FROM AUTHOR]

Biodegradable poly(ε -caprolactone-co-lactide)- b -poly(ethylene glycol)- b -poly(ε -caprolactone- co -lactide) (PCLA-PEG-PCLA) triblock copolymer was developed to prepare thermosensitive inks for digital fiber printing applications. The thermosensitive inks can be printed on any textile or fiber that does not need to go through the pretreatment and soaping procedure like traditional inks. This copolymer aqueous solution has a reversible sol–gel transition property, which can be used to prepare thermosensitive sol–gel inks. PCLA-PEG-PCLA had little effect on the physical properties of the inks, including the average particle size, conductivity, and surface tension at room temperature. However, the viscosity of the thermosensitive inks can increase dramatically under high temperature. This was due to the inks undergoing a sol–gel transition with an increase of temperature. The inks were in the sol state in the printer cartridge at room temperature and when the ink drops fell on the heated fiber or textile, a sol–gel transition occurred and turned them into a gel immediately. The high viscosity prevented the ink from spreading around on the fabrics, thus giving a sharp edge. The study indicated that the line width printed by thermosensitive inks was reduced to 266.35 μm from 464.08 μm in the weft direction (reduced by 43%), and the line width in the warp direction was reduced to 264.35 μm from 385.76 μm (reduced by 32%). The polyester fabric printed by thermosensitive ink has a higher color strength (K / S) at 47–50°C with excellent colorfastness. Thermosensitive ink is a type of innovative ink, in line with the concept of green ecological textile manufacturing. [ABSTRACT FROM AUTHOR]

New biodegradable aliphatic PLLA-PBA-PLLA copolymers with soft poly(butylene adipate) (PBA) and hard poly(l-lactide) (PLLA) building blocks were synthesized via ring-opening polymerization (ROP). Proton nuclear magnetic resonance (1HNMR) was utilized to confirm the volume fraction of PBA (fPBA) within PLLA-PBA-PLLA. It was found that a PBA midblock (PBA-mid) within PLLA-PBA-PLLA-s (PLLA-PBA-PLLA triblock copolymer with a short PLLA block length) might display lamellar domain structure. However, PBA-mid within PLLA-PBA-PLLA-l (PLLA-PBA-PLLA triblock copolymer with a long PLLA block length) might locate itself as a nanoscale cylindrical domain surrounded by a PLLA continuous phase. Polymorphic crystals of PBA-mid within the PLLA-PBA-PLLA copolymers were formed after melt crystallization at the given temperatures, which were studied by differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) analysis. According to the WAXD and DSC analyses, it was interesting to find that the α-type crystal of PBA-mid was favorable to develop in the lower temperature region regardless of the state (crystallization or amorphous) of the PLLA component. Additionally, when the PLLA component was held in its amorphous state, it was easier for PBA-mid within the PLLA-PBA-PLLA copolymers to transform from the metastable β-form crystal to the stable α-form crystal. Furthermore, polarized optical microscopy (POM) photos provided direct evidence of the polymorphic crystals of PBA-mid within PLLA-PBA-PLLAs. [ABSTRACT FROM AUTHOR]

Inspired by the striated structure of skeletal muscle fibers, a polymeric actuator by assembling two symmetric triblock copolymers, namely, polystyrene‐b‐poly(acrylic acid)‐b‐polystyrene (SAS) and polystyrene‐b‐poly(ethylene oxide)‐b‐polystyrene (SES) is developed. Owing to the microphase separation of the triblock copolymers and hydrogen‐bonding complexation of their middle segments, the SAS/SES assembly forms a lamellar structure with alternating vitrified S and hydrogen‐bonded A/E association layers. The SAS/SES strip can be actuated and operate in response to environmental pH. The contraction ratio and working density of the SAS/SES actuator are approximately 50% and 90 kJ m−3, respectively; these values are higher than those of skeletal muscle fibers. In addition, the SAS/SES actuator shows a "catch‐state", that is, it can maintain force without energy consumption, which is a feature of mollusc muscle but not skeletal muscle. This study provides a biomimetic approach for the development of artificial polymeric actuators with outstanding performance. [ABSTRACT FROM AUTHOR]

The interactions of egg yolk phosphatidylcholine liposomes with F108 and F127 triblock copolymers, in the monomer state, were analyzed by isothermal titration calorimetry (ITC) at 37 °C. According to the results, the critical micelle concentration was determined to be 0.4 and 0.04 wt.% for F108 and F127, respectively, by surface tension at 37 °C. According to the results, liposomes/poloxamers were not favoured energetically, since endothermic interactions were observed. However, positive changes in entropy promoted a spontaneous process. F127 had a greater partition coefficient (51.97 ± 1.77 × 104), stronger affinity, than F108 (8.19 ± 0.37 × 104) towards the vesicle lipid bilayer due to its larger hydrophobic block. After the ITC experiments, an increased vesicle size (within about 1–3 nm average) by dynamic light scattering and the formation of bilayer discs by electron microscopy (EM) was observed at low copolymer concentrations (0.57 mol% of F108 and 1.01 mol% of F127). The EM and ITC results confirmed the intimate association of the copolymers with the membrane instead of being simply absorbed onto the bilayer surface. Our results indicate that the temperature of the system (37 °C), the copolymer concentration and hydrophobic chain length are important factors for the interaction of poloxamers with lipid bilayers and the stability of liposomes. [ABSTRACT FROM AUTHOR]

Associations of amphiphiles assume their various morphologies according to the so‐called packing parameter under thermodynamic control. However, one may raise the question of whether polymers can always relax fast enough to obey thermodynamic control, and how this may be checked. Here, a case of polyion complex (PIC) assemblies where the morphology appears to be subject to kinetic control is discussed. Poly (ethylene oxide)‐b‐(styrene sulfonate) block copolymers are combined with cationic PAMAM dendrimers of various generations (2–7). The PEO‐PSS diblocks, and the corresponding PSS‐PEO‐PSS triblocks should have nearly identical packing parameters, but surprisingly creat different assemblies, namely core‐shell micelles and vesicles, respectively. Moreover, the micelles are very stable against added salt, whereas the vesicles are not only much more sensitive to added salt, but also appear to exchange matter on relevant time scales. The small and largely quenched early‐stage precursor complexes are responsible for the morphological and dynamic differences, implying that kinetic control may also be a way to obtain particles with well‐defined and useful properties. The exciting new finding that triblocks produce more "active" vesicles will hopefully trigger the exploration of more pathways, and so learn how to tune PICsomes toward specific applications. [ABSTRACT FROM AUTHOR]

Surface‐initiated polymerization of various monomers (methacrylic acid, methacrylate, acrylate, acrylamide, and zwitterionic monomer) is conducted to form triblock copolymer brushes using oxygen‐initiated reversible addition−fragmentation chain‐transfer polymerization in the presence of air. An ellipsometry analysis, water contact angle analysis, X‐ray photoelectron spectroscopy, and atomic force microscopy confirm the successful formation of polymer brushes with complex architectures on a silicon substrate. [ABSTRACT FROM AUTHOR]

In human body, alveoli are the primary sites for gas exchange which are formed by the dilation and protrusion of bronchioles at the end of the lung, and the rapid gas‐exchanging process in the alveoli ensures normal life activities. Based on the unique structures and functions of alveoli, it is necessary to study the regulation mechanism of its formation, respiration, and apoptosis. Herein, a class of reversible addition−fragmentation chain transfer (RAFT)‐derived amphiphilic triblock copolymers, PEO‐b‐P(DEAEMA‐co‐FMA)‐b‐PS is designed and synthesized. Due to the amphiphilic and gas‐responsive segments, these triblock copolymers can self‐assemble in aqueous solution and undergo the morphological transition from nanotubes to vesicles under gas stimulation; meanwhile, in the cycles of CO2/O2 stimulation, these vesicles can further realize the volume expansion and contraction, eventually rupture. The gas‐driven morphological transformations of these aggregates successfully imitate the formation, respiration, and apoptosis of alveoli, and provide an essential basis for revealing the life phenomena. [ABSTRACT FROM AUTHOR]

Despite the outstanding role of mesoscopic structures on the efficiency and stability of perovskite solar cells (PSCs) in the regular (n–i–p) architecture, mesoscopic PSCs in inverted (p–i–n) architecture have rarely been reported. Herein, an efficient and stable mesoscopic NiOx (mp‐NiOx) scaffold formed via a simple and low‐cost triblock copolymer template‐assisted strategy is employed, and this mp‐NiOx film is utilized as a hole transport layer (HTL) in PSCs, for the first time. Promisingly, this approach allows the fabrication of homogenous, crack‐free, and robust 150 nm thick mp‐NiOx HTLs through a facile chemical approach. Such a high‐quality templated mp‐NiOx structure promotes the growth of the perovskite film yielding better surface coverage and enlarged grains. These desired structural and morphological features effectively translate into improved charge extraction, accelerated charge transportation, and suppressed trap‐assisted recombination. Ultimately, a considerable efficiency of 20.2% is achieved with negligible hysteresis which is among the highest efficiencies for mp‐NiOx based inverted PSCs so far. Moreover, mesoscopic devices indicate higher long‐term stability under ambient conditions compared to planar devices. Overall, these results may set new benchmarks in terms of performance for mesoscopic inverted PSCs employing templated mp‐NiOx films as highly efficient, stable, and easy fabricated HTLs. [ABSTRACT FROM AUTHOR]

A triblock copolymer with hydrophobic end blocks and a polyampholytic middle block is investigated in a mixture of water and acetone with a focus on the dependence of the rheological properties and of the micellar structure and correlation on the content of acetone. The polymer under study is PMMA86-b-P(DEA190-co-MAA96)-b-PMMA86, where PMMA stands for poly(methyl methacrylate) and P(DEA-co-MAA) for poly(2-(diethylamino) ethyl methacrylate-co-methacrylic acid). The pH is chosen at 3. Rheological measurements reveal a transition from a viscoelastic solid over a viscoelastic liquid to a freely flowing liquid upon addition of 5 or 10 wt% of acetone to a 3 wt% aqueous polymer solution, respectively. Using small-angle neutron scattering on 0.5 wt% polymer solutions in water/acetone with the content of the latter ranging between 0 and 30 wt%, significant structural changes are observed as well, such as a decrease of the distance between the PMMA cross-links and of the size of the network clusters upon increasing acetone constant. These changes are attributed to the reduction of the dielectric constant by the addition of the cosolvent acetone, enhancing the flexibility of the middle blocks and their tendency to backfolding, as well as to the decrease of the solvent selectivity, inducing significant exchange rate enhancement of the core-forming PMMA blocks. [ABSTRACT FROM AUTHOR]

We perform a comprehensive Monte Carlo study of the ABA triblock self-assembly by the Cooperative Motion Algorithm. Our attention is focused on three series of triblocks which are grown from parent AB diblocks of varying asymmetry. Unlike the previous studies in which the total length of the chain varies upon growing the terminal A-block, here we keep the fixed chain length for a given series. Moreover, we determine the order-disorder transition temperature as the parameter (being the ratio of the grown A-block to the length of the parent diblock) increases. In this case we find that the order-disorder transition temperature monotonically decreases for two asymmetric series which is different from the non-monotonic depression of TODT reported previously. We also construct a phase diagram which shows a variety of nanostructures as is increased. [ABSTRACT FROM AUTHOR]

ABA and BAB triblock amphiphilic copolymers based on sucrose methacrylate and methyl methacrylate are synthesized by sequential reversible addition–fragmentation chain transfer polymerization using S,S′‐bis(R,R′‐dimethyl‐R′′‐acetic acid)‐trithiocarbonate as a chain transfer agent. The copolymers present narrow molar mass dispersity, controlled molar mass and architecture as determined by gel permeation chromatography and 1H and 13C nuclear magnetic resonance. The copolymers with molar and mass fractions of poly(sucrose methacrylate) block ranging from 1 to 22 mol% and 3 to 52 wt%, respectively, and different molar masses present characteristics of a surfactant such as self‐assembly. The self‐assembly of the triblock copolymers in water, N,N‐dimethylformamide (DMF), dichloromethane, tetrahydrofuran, or benzene results mostly in vesicles as confirmed by scanning electron microscopy images and small‐angle X‐ray of the dispersions. Moreover, the copolymers present the capability to stabilize aromatic molecules (Nile Red dye) and nonpolar solvents in an aqueous phase and polar ionic molecules (methylene blue) and water in a nonpolar medium, suggesting the potential for application in drug encapsulation, environmental remediation systems, and molecular extraction in liquid–liquid immiscible systems, for example. Films prepared by casting from copolymer solutions in DMF present a lamellar structure with the lamellar thickness varying according to the copolymer molar mass. [ABSTRACT FROM AUTHOR]

The poly(l -lactide-b-ethylene glycol-b- l -lactide) (PLLA-PEG-PLLA) triblock copolymers with different chain segment length are fabricated by ring-opening polymerization. The structure, molecular weight, and crystallization behaviors of the triblock copolymers are characterized by Fourier transform infrared, nuclear magnetic resonance spectroscopy, gel permeation in chromatography, X-ray diffraction, differential scanning calorimetry, and polarizing optical microscopy (POM). The results show that the increase of block length is beneficial to improve its crystallization. In addition, the triblock copolymer exhibits a double crystallization phenomenon. The POM results indicate that PEG and PLLA chains of the copolymer crystallize in their respective crystallization temperature regions. The growth rate of the PLLA spherocrystal decreases and the dendritic spherocrystals appear with increasing the PEG chain length when the PLLA chain of the copolymer is isothermal crystallized at 80°C and PLLA chain length is constant. The growth rate of the PEG spherocrystal decreases and the spherocrystal morphology changes little with increasing PLLA chain length when the PEG chain is isothermal crystallized at 25°C and the length of PEG chain remained unchanged. [ABSTRACT FROM AUTHOR]

Mechanical properties including the failure behavior of physically assembled gels or physical gels are governed by their network structure. To investigate such behavior, we consider a physical gel system consisting of poly(styrene)‐poly(isoprene)‐poly(styrene)[PS‐PI‐PS] in mineral oil. In these gels, the endblock (PS) molecular weights are not significantly different, whereas, the midblock (PI) molecular weight has been varied such that we can access gels with and without midblock entanglement. Small angle X‐ray scattering data reveals that the gels are composed of collapsed PS aggregates connected by PI chains. The gelation temperature has been found to be a function of the endblock concentration. Tensile tests display stretch‐rate dependent modulus at high strain for the gels with midblock entanglement. Creep failure behavior has also been found to be influenced by the entanglement. Fracture experiments with predefined cracks show that the energy release rate scales linearly with the crack‐tip velocity for all gels considered here. In addition, increase of midblock chain length resulted in higher viscous dissipation leading to a higher energy release rate. The results provide an insight into how midblock entanglement can possibly affect the mechanical properties of physically assembled triblock copolymer gels in a midblock selective solvent. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 1014–1026 [ABSTRACT FROM AUTHOR]

To develop carbon dioxide-reducible polymeric materials, triblock copolymers (PLA-polyester-PLA) of enantiomeric lactides and biopolyester diol, were synthesized by the ring-opening polymerization of lactide in the presence of diol using stannous octoate. The results showed that the incorporation of the biopolyester decreases the crystallinity and melting temperature of PLA. However, the blend of enantiomeric PLA copolymers revealed more thermal stability than homo- and copolymers. It was due to the formation of stereocomplexes between enantiomeric PLAs. The topographic images of degradation showed that the degradation rate of a copolymer was faster than of PLA while that of stereocomplex became much slower. [ABSTRACT FROM AUTHOR]

Recent years have seen an increased interest in the use of ABC triblock terpolymers to bottom‐up assemble multicompartment patchy nanoparticles. Despite these experimental and theoretical efforts, the applications of polymer‐based patchy nanoparticles remain rather limited. One of the major challenges that eclipses their potential is the lack of knowledge to selectively encapsulate cargoes within different compartments that are separated in the nanometer length scale. Here, strategies are reported to segregate two chemically distinct molecules in either the patches or core compartment of patchy nanoparticles that bear a (bioactive) sugar corona. The potential use of these bioactive patchy nanoparticles containing compartmentalized cargoes for simultaneous drug delivery with real‐time release monitoring capabilities is further demonstrated. [ABSTRACT FROM AUTHOR]

In order to create a new drug delivery system, the ibuprofen-loaded triblock copolymer PCL/PEO/PCL (PCEC) microspheres with a low PEO content (<2 wt%) were prepared by oil in water (o/w) solvent evaporation technique. The influence of PEO content, molecular weight of a polymer matrix and drug loading on the ibuprofen release profiles were evaluated. The interactions between polymer matrix and ibuprofen were detected by FTIR analysis. The presence of hydrophilic PEO segment in PCL chains caused the decrease in particle size, which further had a great impact on the drug release kinetics, i.e., initially faster release and significantly higher quantity of released drug compared to neat PCL. Ibuprofen release behavior from polymer matrix was governed by a diffusion process. In vitro cytotoxicity tests revealed that empty PCL and PCEC microspheres were not toxic at low concentrations, while ibuprofen-loaded microspheres exhibited cytotoxicity correlated with amounts of incorporated drug. [ABSTRACT FROM AUTHOR]

Three different ABA‐type triblock copolymers each containing biodegradable aliphatic polycarbonate as the middle block and poly(l‐lactide) as the outer blocks were synthesized and the influence of the methylene chain length of the aliphatic polycarbonate middle block on various properties of the triblock copolymers was evaluated. Differential scanning calorimetry and wide‐angle X‐ray diffraction studies revealed that the incorporation of the outer blocks reduced the crystallinity of the middle aliphatic polycarbonate block. Variation of methylene chain length of the middle block led to a change in morphology from spherical to cylindrical as evidenced from atomic force microscopy studies. In addition, the mechanical properties of the block copolymers showed semi‐ductile to quasi‐brittle behaviour depending upon the composition of the middle block which was also confirmed using scanning electron microscopy. Dynamic mechanical analysis of the triblock copolymers indicated that storage modulus increased with a decrease in methylene chain length. © 2018 Society of Chemical Industry This study demonstrates that by changing the aliphatic polycarbonate middle block of a triblock copolymer, the morphology and mechanical properties of the triblock copolymer can be tailored. [ABSTRACT FROM AUTHOR]

The effect of different polyoxyethylene–polyoxypropylene triblock copolymers, their concentration, and mode of action on the loading of poly-(lactic-co-glycolic acid) copolymer-based microparticles containing such medicinal agents as radachlorin (chlorin e6) or ethidium bromide in mesenchymal stem cells was studied. It has been shown that medicinal agents encapsulated inside microparticles affect the loading of these particles in the cytoplasm of mesenchymal stem cells. The number of cells that absorbed the particles with chlorin e6 is approximately two times lower than that in the experiments with ethidium bromide. It has been shown that pretreatment of microparticles with triblock copolymers is more efficient for loading them in cells compared with simultaneous introduction of triblock copolymers and particles into the culture medium. Treatment of ethidium bromide-containing microparticles with triblock copolymers is not efficient for their loading in mesenchymal stem cells compared to the control. The exception is Pluronic 123; when particles are treated with it at concentrations of 1 and 2%, the loading of particles in cells increases compared to the control by factors of approximately 11 and 5, respectively. For particles with chlorin e6, their pretreatment with triblock copolymers at a concentration of 4% is most efficient; the loading of the pretreated particles in cells is increased by factors of approximately 3 to 11. [ABSTRACT FROM AUTHOR]

A series of tertiary amine containing PHMEMA-PEG-PHMEMA ABA triblock copolymers were synthesized by atom transfer radical polymerization (ATRP) using bromine-capped poly(ethylene glycol) (Br-PEG-Br) and 2-(hexamethyleneimino)ethyl methacrylate (HMEMA) as macro-initiator and monomers, respectively. The chemical structures and molecular weights of triblock copolymers were characterized by 1H NMR and gel permeation chromatography (GPC). The self-assembly behaviors of copolymers in different pH conditions were studied by dynamic light scattering (DLS) and transmission electron microscopy (TEM). Triblock copolymers self-assembled into micelles in water (pH 7.4) and the micelles disassembled at acidic pH (pH 5.0). Anticancer drug doxorubicin (DOX) was used as a drug model and physically encapsulated into polymeric micelles. The drug release of DOX-loaded polymeric micelles was pH-responsive; the drug-loaded micelles that had higher contents of tertiary amine in polymer pendant groups showed faster release speed. In addition, the drug-loaded micelles showed excellent inhibition efficacy against HeLa cells in vitro. [ABSTRACT FROM AUTHOR]

Hydrolytic, enzymatic degradation and composting under controlled conditions of series of triblock PCL/PEO copolymers, PCEC, with central short PEO block (Mn 400 g/mol) are presented and compared with homopolymer (PCL). The PCEC copolymers, synthesized via ring-opening polymerization of ε-caprolactone, were characterized by 1H NMR, quantitative 13C NMR, GPC, DSC and WAXS. The introduction of the PEO central segment (< 2 wt%) in PCL chains significantly affected thermal degradation and crystallization behavior, while the hydrophobicity was slightly reduced as confirmed by water absorption and moisture uptake experiments. Hydrolytic degradation studies in phosphate buffer after 8 weeks indicated a small weight loss, while FTIR analysis detected changes in crystallinity indexes and GPC measurements revealed bulk degradation. Enzymatic degradation tested by cell-free extracts containing Pseudomonas aeruginosa PAO1 confirmed high enzyme activity throughout the surface causing morphological changes detected by optical microscopy and AFM analysis. The changes in roughness of polymer films revealed surface erosion mechanism of enzymatic degradation. Copolymer with the highest content of PEO segment and the lowest molecular weight showed better degradation ability compared to PCL and other copolymers. Furthermore, composting of polymer films in a model compost system at 37 °C resulted in significant degradation of the all synthesized block copolymers. [ABSTRACT FROM AUTHOR]

Poly(ϵ-caprolactone)-b-poly(ethylene glycol)-b-poly(ϵ-caprolactone) (PCL-b-PEG-b-PCL) triblock copolymer were synthesized by mean anionic activation of the hydroxyl end groups of poly(ethylene glycol) in presence of diphenylmethylsodium. Copolymers were characterized by SEC, FT-IR and 1H-NMR spectroscopy, TGA and DSC. Size exclusion chromatographic analysis of obtained copolymers indicated incorporation of CL monomer into PEG without formation of PCL homopolymer. Characterization by FT-IR and 1H NMR spectroscopy of the resulting polymeric products, with respect to their structure, end-groups and composition, showed that they are best described as ester-ether-ester triblock copolymers, whose compositions can be adjusted changing the feeding molar ratio of PEG to CL. The thermal stability of triblock copolymers was less that PEG precursor, but higher that PCL homopolymer. Analysis by mean DSC showed that all copolymers were semi-crystalline and their thermal behavior depending on their composition. [ABSTRACT FROM AUTHOR]

Abstract: High‐performance n‐type thermoelectric polymers are vital in the development of polymer thermoelectric generators (PTEGs). However, the progress is very slow due to their low stability and low thermoelectric properties. Here, aniline oligomer‐block‐polyethylene glycol‐block‐aniline oligomer (ANI)n‐b‐PEO‐b‐(ANI)n) (n = 4, 8, 16) are prepared and studied. The results indicate that the (ANI)n‐b‐PEO‐b‐(ANI)n show unique temperature sensitivity and switch from p‐type to n‐type when the temperature is above 300 K. Differential scanning calorimetry curves show that the Tg of the (ANI)n‐b‐PEO‐b‐(ANI)n is lower than 300 K, indicating that PEO segments of the (ANI)n‐b‐PEO‐b‐(ANI)n easily move above 300 K and have high flexibility. Temperature‐dependent Raman spectra confirm that there are strong interactions between PEO segments and aniline oligomers during the raising temperature, and PEO chains might provide plenty of negative charge at high temperature, which can convert the (ANI)n‐b‐PEO‐b‐(ANI)n into n‐type thermoelectric materials. To adjust the number of aniline unit, (ANI)8‐b‐PEO‐b‐(ANI)8 shows excellent n‐type characteristics with Seebeck coefficient as large as −1171 µV K−1 at 381 K. The strong interaction between PEO and aniline oligomers plays a dominant role in the n‐type thermoelectric performance of the triblock copolymers, which have potential application in the field of PTEGs and temperature sensors. [ABSTRACT FROM AUTHOR]

Nonionic surfactants, triblock copolymers (TBCs), were used to obtain and stabilize perfluorocarbon emulsions in a water solution (drop size, 200-300 nm). These TBCs differ in their molecular weight, length of polyethylene glycol (PEG) or polypropylene glycol (PPG) chains, and the ΣPEG/ΣPPG parameter value. Direct dependence is found between the amount of plasma proteins adsorbed on drops and the PEG/PPG value. The amount of the adsorbed proteins and their total mass per unit surface of the drop decreases as this ratio is reduced. Meanwhile, protein adsorption is almost independent of the molecular weight of TBCs and the length of PEG and PPG blocks. Adsorption of non-protein substance, chlorine e6, on emulsion drops increases with the rising ΣPEG/ΣPPG value and does not depend on other characteristics of TBC used as a stabilizer. [ABSTRACT FROM AUTHOR]

Abstract: Well‐defined β‐cyclodextrin (β‐CD)‐terminated double hydrophilic diblock copolymers (DHBCs), β‐CD‐ poly(di(ethylene glycol) methyl ether methacrylate) (PMEO2MA)‐b‐poly(2‐(diethylamino)ethyl methacrylate) (PDEA) (BP1) and β‐CD‐PDEA‐b‐PMEO2MA (BP2), are synthesized via sequential atom transfer radical polymerizations of di(ethylene glycol) methyl ether methacrylate and 2‐(diethylamino)ethyl methacrylate using alkynyl‐functionalized initiator, followed by click reactions with an excess of mono‐azido‐substituted β‐cyclodextrin (β‐CD‐N3). The micellization behavior of these as‐prepared DHBCs in aqueous solutions suffers from insufficient colloidal stabilities at basic pH and high temperatures (e.g., pH 9 and 45 °C), resulting in the formation of macroscopic precipitations. However, the stabilities of colloidal nanoparticles can be remarkably enhanced as a result of the convenient formation of three‐layered micelles by taking advantage of host–guest interactions of BP1/BP2 and Ad‐terminated poly(ethylene glycol). The pH‐ and thermoresponsive three‐layered micelles with enhanced stability may augur promising applications in targeted drug delivery and controlled intelligent release. [ABSTRACT FROM AUTHOR]

Template-free fabrication of non-spherical polymeric nanoparticles is desirable for various applications, but has had limited success owing to thermodynamic favorability of sphere formation. Herein we present a simple way to prepare cubic nanoparticles of block copolymers by self-assembly from aqueous solutions at room temperature. Nanocubes with edges of 40-200 nm are formed spontaneously on different surfaces upon water evaporation from micellar solutions of triblock copolymers containing a central poly(ethylene oxide) block and terminal trimethylene carbonate/dithiolane blocks. These polymers self-assemble into 28±5 nm micelles in water. Upon drying, micelle aggregation and a kinetically controlled crystallization of central blocks evidently induce solid cubic particle formation. An approach for preserving the structures of these cubes in water by thiol- or photo-induced crosslinking was developed. The ability to solubilize a model hydrophobic drug, curcumin, was also explored. [ABSTRACT FROM AUTHOR]

The content of styrene units in nonhydrogenated and hydrogenated styrene-butadiene-styrene and styrene-isoprene-styrene triblock copolymers significantly influences product performance. A size exclusion chromatography method was developed to determine the average styrene content of triblock copolymers blended with tackifier in adhesives. A complete separation of the triblock copolymer from the other additives was realized with size exclusion chromatography. The peak area ratio of the UV and refraction index signals of the copolymers at the same effective elution volume was correlated to the average styrene unit content using nuclear magnetic resonance spectroscopy with commercial copolymers as standards. The obtained calibration curves showed good linearity for both the hydrogenated and nonhydrogenated styrene-butadiene-styrene and styrene-isoprene-styrene triblock copolymers ( r = 0.974 for styrene contents of 19.3-46.3% for nonhydrogenated ones and r = 0.970 for the styrene contents of 23-58.2% for hydrogenated ones). For copolymer blends, the developed method provided more accurate average styrene unit contents than nuclear magnetic resonance spectroscopy provided. These results were validated using two known copolymer blends consisting of either styrene-isoprene-styrene or hydrogenated styrene-butadiene-styrene and a hydrocarbon tackifying resin as well as an unknown adhesive with styrene-butadiene-styrene and an aromatic tackifying resin. The methodology can be readily applied to styrene-containing polymers in blends such as poly(acrylonitrile-butadiene styrene). [ABSTRACT FROM AUTHOR]

ABSTRACT The micellization of three tailor-made triblock copolymers, such as PB100-P2VP100-PEO104, PB185-P2VP108-PEO154, and PB37-P2VP115-PEO241, having similar total molecular weights and constant poly(2-vinylpyridine) (P2VP) sequence lengths, was investigated as a function of pH and sodium dodecyl sulfate (SDS) concentration. At pH 7 the formation of intermicellar aggregates was observed, especially for copolymers of low poly(ethylene oxide) (PEO) content. A pH decrease from 7 to 3 leads to a particle size increase due to the electrostatic repulsion of the protonated P2VP chains. The influence of the PEO sequence length was also observed for zeta potential values. At pH 3, in the absence of SDS, core-shell-corona micelles are formed whereas in the presence of small amount of SDS (degree of neutralization DN = 0%-50%), a complex is formed between SDS and the protonated P2VP which leads to the shrinkage of the shell and thus to a decrease of the micellar sizes. For higher DN values, the micellar sizes increase due to the formation of large agglomerates and a transition occurs from a monomodal to a bimodal size distribution. Furthermore, it turned out that secondary aggregation, such as intermicellar aggregation, can completely be avoided if the degree of polymerization (DPn) of the water-soluble block is significantly higher than the DPn of the water-insoluble sequence. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45313. [ABSTRACT FROM AUTHOR]

The present research concerns with the preparation and characterization of isobutylene isoprene/butadiene-styrene rubber (IIR/SBR) blends with different blend ratios, in the presence and absence of styrene-isoprene-styrene (SIS) and styrene-isobutylene-styrene (SiBS) triblock copolymers to be tested as compatibilizers. Effect of the triblock copolymers on the blend homogeneity was investigated with the aid of scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) measurements. Characterization of the rubber blends was conducted by measuring the physico-mechanical properties after and before thermal aging, in presence and absence of the triblock copolymers. In addition, weight swell % in toluene, motor oil and brake fluid of the rubber blend vulcanizates was assessed. The incorporation of SIS and SiBS triblock copolymers improved the homogeneity of IIR/SBR blends as well as increased both tensile strength and elongation at break of the rubber blend vulcanizates. Of the entire blend ratios examined, IIR/SBR (25/75) blend containing SIS compatibilizer possessed the best physico-mechanical properties (12.6 MPa tensile strength and 425 % elongation at break) and (14 MPa tensile strength and 555 % elongation at break) after and before thermal aging, respectively. Utilization of SIS and SiBS triblock copolymers enhanced the thermal stability of IIR/SBR blend vulcanizates. Moreover, IIR/SBR blends of different blend ratios showed superior swelling resistance in the brake fluid. IIR/SBR (25/75) blend containing SIS compatibilizer and cured with CBS/ZDEC/S vulcanizing system possessed the best physico-mechanical properties (14.4 MPa tensile strength and 440 % elongation at break) and (16.5 MPa tensile strength and 610 % elongation at break) after and before thermal aging, respectively. [ABSTRACT FROM AUTHOR]

A series of well-defined thermoresponsive ABA-type triblock copolymers poly( N-isopropylacrylamide)- b-poly( n-octadecylacrylate)- b-poly( N-isopropylacrylamide) (PNIPAAm- b-PODA- b-PNIPAAm) consisting of two blocks of PNIPAAm and one block of PODA in different ratio are prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization. The structures of the copolymers are characterized by HNMR. All block copolymers show lower critical micelle concentration (CMC) (<10 mg/L) in water, indicating the strong tendency of the triblock copolymers to self-assemble into highly stable micelles. It is interesting that the resulting micelles demonstrate double lower critical solution temperature (LCST) behavior. Dynamic light-scattering (DLS) experiments show that the micelles are well dispersed at nanoscale and have a narrow size distribution. Moreover, the drug-loading behavior of micelles is further investigated. The high drug encapsulation efficiency indicates the potential of micelles formed from PNIPAAm- b-PODA- b-PNIPAAm as drug carriers. [ABSTRACT FROM AUTHOR]

The preparation of physically crosslinked hydrogels from quasi ABA-triblock copolymers with a water-soluble middle block and hydrophobic end groups is reported. The hydrophilic monomer N-acryloylmorpholine is copolymerized with hydrophobic isobornyl acrylate via a one-pot sequential monomer addition through reversible addition fragmentation chain-transfer (RAFT) polymerization in an automated parallel synthesizer, allowing systematic variation of polymer chain length and hydrophobic-hydrophilic ratio. Hydrophobic interactions between the outer blocks cause them to phase-separate into larger hydrophobic domains in water, forming physical crosslinks between the polymers. The resulting hydrogels are studied using rheology and their self-healing ability after large strain damage is shown. [ABSTRACT FROM AUTHOR]

ABSTRACT Aqueous solution properties of amphiphilic P(AA- co- tBA)- b-PPO- b- P(AA- co- tBA) copolymers having various tBA contents are presented in this article. These copolymers show pH-sensitive behavior depending on tBA/AA ratio. Hydrophobic interactions between tBA units leading to pH-dependent macroscopic aggregates were evidenced by turbidimetry. The aggregation behavior of the PPO middle block was concealed in presence of tBA units. The formation of water-soluble aggregated objects was characterized by Asymmetrical Flow Field Flow Fractionation (AsF4). By increasing tBA/AA ratio, we observed an increase of aggregates size as well as a reduction of the critical concentration aggregation. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 1944-1949 [ABSTRACT FROM AUTHOR]

The self-assembly behavior of sphere-forming RCR triblock copolymers within a planar slit is studied by performing dissipative particle dynamics simulations. A sequence of novel structures which are not observed in bulk are formed within slits, including wetting layers, island-like structure, parallel cylinders, perpendicular cylinders and cross-cylindrical structures. Perpendicular cylinders are always formed before the increase in the layers of parallel cylinders. A phase diagram of the assembled structures with respective to the slit property and height is thus presented. The rod length is found to have a significant impact on the rod alignment, and a disordered-ordered transition of rod orientation occurs with an increase in the length of rod blocks. Some special structures, such as parallel half-cylinders and arrowhead-shaped morphology, are observed when the rod length increases to a certain extent. Our results show that the property and height of the slit and rod length all influence the self-assembly of rod-coil-rod triblock copolymers. [ABSTRACT FROM AUTHOR]

This study was conducted to synthesize poly(L-lactide)–poly(ethylene glycol)–poly(L-lactide) triblock copolymer (PEGLA) with different poly(L-lactide) block length, and explore its applicability in a blend with linear poly(L-lactide) (3051D NatureWorks) with the intention of improving heat seal and adhesion properties at extrusion coating on paperboard. Poly(L-lactide)–poly(ethylene glycol)–poly(L-lactide) was obtained by ring opening polymerization ofL-lactide using poly(ethylene glycol) (molecular weight 6000 g mol−1) as an initiator and stannous octoate as catalyst. The structures of the PEGLAs were characterized by proton nuclear magnetic resonance spectroscopy. The melt flow and thermal properties of all PEGLAs and their blends were evaluated using dynamic rheology and differential scanning calorimeter. All blends containing 10 wt% of PEGLAs displayed similar zero shear viscosities to neat poly(L-lactide), while blends containing 30 wt% of PEGLAs showed slightly higher zero shear viscosity. However, all blends displayed higher shear thinning and increased melt elasticity (based on tan δ). No major changes in thermal properties were distinguished from differential scanning calorimetric studies. High molecular weight PEGLAs could be used in extrusion coating with 3051D without problems. [ABSTRACT FROM PUBLISHER]

Ethylene-propylene-methyl methacrylate (MMA) and ethylene-hexene-MMA A-B-C block copolymers with high molecular weight (>100 000) are synthesized using fluorenylamide-ligated titanium complex activated by modified methylaluminoxane and 2,6- di- tert-butyl-4-methylphenol for the first time. After diblock copolymerization of olefin is conducted completely, MMA is added and activated by aluminum Lewis acid to promote anionic polymerization. The length of polyolefin and poly (methyl methacrylate) (PMMA) is controllable precisely by the change of the additive amount of olefin and polymerization time, respectively. A soft amorphous polypropylene or polyhexene segment is located between two hard segments of semicrystalline polyethylene and glassy PMMA blocks. [ABSTRACT FROM AUTHOR]

ABSTRACT Polymers consisting of poly(acrylic acid) (PAA) and statistical poly[(acrylic acid)- co-( tert-butylacrylate)] (P(AA- co- tBA)), attached to both extremities of Jeffamine® (D series based on a poly(propylene oxide) (PPO) with one amine function at each end) using atom transfer radical polymerization (ATRP) are presented in this article. An original bifunctional amide-based macroinitiator was first elaborated from Jeffamine®. tBA polymerization was subsequently initiated from this macroinitiator. This polymerization occurs in a well-controlled manner leading to narrow molecular weights distribution. Amphiphilic copolymers were finally obtained after complete or partial hydrolysis of the P tBA blocks into PAA. The control of the partial hydrolysis of tBA units, conducted in a concentrated HCl/tetrahydrofuran mixture, is demonstrated. The properties of the triblock copolymers were preliminary investigated in aqueous solution by absorbance, DLS measurements and SEC/MALS/DV/DRI analysis as a function of temperature and pH modifications, providing evidences of thermo- and pH-sensitive self-assembly of the copolymers. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 2606-2616 [ABSTRACT FROM AUTHOR]

Three dimensional self-consistent field theoretic simulations have been performed to determine the equilibrium morphologies formed by linear ABC triblock polymer melts confined between two parallel plates that favor the middle block. Our primary goal is to elucidate the conditions under which the perpendicular lamella is stabilized, since this morphology plays a central role in many nanotechnology applications. Key factors, namely, the chain architecture, surface energy and the mismatch between the film thickness d and the bulk lamella period, LO, determine the final morphologies, e.g., perpendicular and parallel lamella, perforated lamella and wet substrate with parallel cylinders in the core, have been identified. Overall, our findings are fully consistent with the results of limited experimental studies focused on morphology development in thin films of triblock polymer melts. Finally, we have clearly demonstrated that ABC triblocks hold technological advantages over diblocks for nano-lithographic fabrications. [ABSTRACT FROM AUTHOR]

Star-like amphiphilic triblock copolymers were rationally designed and synthesized by combining two sequential atom-transfer radical polymerization reactions with a click reaction. Subsequently, a family of uniform magnetic/plasmonic core/shell nanoparticles was crafted by capitalizing on these triblock copolymers as nanoreactors. The diameter of the magnetic core and the thickness of the plasmonic shell could be independently and accurately controlled by varying the molecular weights (i.e., the chain lengths) of the inner and intermediate blocks of the star-like triblock copolymers, respectively. The surface plasmonic absorption of core/shell nanoparticles with different core diameters and shell thicknesses was systematically studied and theoretically modeled. This robust strategy provides easy access to a large variety of multifunctional nanoparticles with large lattice mismatches for use in optics, optoelectronics, catalysis, or bioimaging. [ABSTRACT FROM AUTHOR]

A series of methyl acrylate-acrylic acid amphiphilic triblock copolymers (PMA-PAA-PMA) were prepared by solution polymerization using S, S′-bis (α,α-dimethy1acetic acid) trithiocarbonate (BDAT) as a reversible addition fragmentation chain transfer (RAFT) agent and methyl acrylate (MA) as the first monomer. The triblock copolymers and their common MA homopolymer precursors were characterized in terms of their compositions, molecular weights and behavior at the air-water interface using H-NMR spectroscopy, thermogravimetric analysis, gel permeation chromatography, surface tension, transmission electron microscopy (TEM) and dynamic light scattering respectively. The results indicated that PMA-PAA-PMA was successfully synthesized through RAFT polymerization. The polydispersity index (PDI) decreased when the molar ratio [ n(MA)/ n(AA)] increased, the lowest PDI was obtained at 5.23 wt% RAFT and the molecular weights were consistent with the theoretical value as the RAFT agent percentage varied. The polymer neutralized by sodium hydroxide solution shows a low critical micelle concentration (CMC), which was <10 mol L in water. The A values increased and showed a maximum with decreased AA chain length. TEM showed that the neutralized polymer formed a special vesicle structure with large pore structure which led to a low CMC and surface tension of water. [ABSTRACT FROM AUTHOR]

ABSTRACT Synthesis of the ABA triblock copolymer nanoparticles of poly( N, N-dimethylacrylamide)- block-polystyrene- block-poly( N, N-dimethylacrylamide) (PDMA- b-PS- b-PDMA) by seeded RAFT polymerization is performed, and the effect of the introduced third poly( N, N-dimethylacrylamide) (PDMA) block on the size and morphology of the PDMA- b-PS- b-PDMA triblock copolymer nanoparticles is investigated. This seeded RAFT polymerization affords the in situ synthesis of the PDMA- b-PS- b-PDMA core-corona nanoparticles, in which the middle solvophobic PS block forms the compacted core, and the first solvophilic PDMA block and the introduced third PDMA block form the solvated complex corona. During the seeded RAFT polymerization, the introduced third PDMA block extends, and the molecular weight of the PDMA- b-PS- b-PDMA triblock copolymer linearly increases with the monomer conversion. It is found that, the size of the PS core in the PDMA- b-PS- b-PDMA triblock copolymer core-corona nanoparticles is almost equal to that in the precursor of the poly( N, N-dimethylacrylamide)- block-polystyrene diblock copolymer core-corona nanoparticles and it keeps constant during the seeded RAFT polymerization, and whereas the introduction of the third PDMA block leads to a crowded complex corona on the PS core. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 1777-1784 [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the effects of size and type of incorporated model molecules on the polymer degradation and release profile from thermosensitive triblock copolymer based controlled delivery systems. In vitro release of the incorporated molecules demonstrated slow release for risperidone (molecular weight (Mw) = 410.48 Da; partition coefficient (Ko/w) = 3.49), while bovine serum albumin (BSA) (Mw = ~66,400 Da; Ko/w = 0.007) and insulin (Mw = 5808 Da; Ko/w = 0.02) showed initial burst release followed by controlled release. The proton NMR, Gel Permeation Chromatography, and Cryo-SEM studies suggest that the size and partition coefficient of incorporated molecules influence the pore size, polymer degradation, and their release. In spite of using a similar polymer delivery system the polymer degradation rate and drug release notably differ for these model molecules. Therefore, size and oil-water partition coefficient are important factors for designing the controlled release formulation of therapeutics from triblock copolymer based delivery systems. [ABSTRACT FROM AUTHOR]

Gastric cancer, a high-risk malignancy, is a genetic disease developing from a cooperation of multiple gene mutations and a multistep process. Gene therapy is a novel treatment method for treating gastric cancer. Here, we developed a novel Arg-Gly-Asp (RGD) peptides conjugated copolymers nanoparticles-based gene delivery system in order to actively targeting inhibit the growth of gastric cancer cells. These transcription factor (AP-2α) expression plasmids were also encapsulated into pluronic triblock copolymers nanoparticles which was constituted of poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (PEO-block-PPO-block-PEO, P123). The size, morphology and composition of prepared nanocomposites were further characterized by nuclear magnetic resonance (NMR), transmission electron microscopy (TEM) and dynamic light scattering (DLS). In MTT (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyltetrazolium bromide) analysis, these nanocomposites have minor effects on the proliferation of GES-1 cells but significantly decreased the viability of MGC-803, suggesting they own low cytotoxicity but good antitumor activity. The following in vivo evaluation experiments confirmed that these nanocomposites could prevent the growth of gastric cancer cells in the tumor xenograft mice model. In conclusion, these unique RGD peptides conjugated P123 encapsulated AP-2α nanocomposites could selectively and continually kill gastric cancer cells by over-expression of AP-2α in vitro and in vivo; this exhibits huge promising applications in clinical gastric cancer therapy. [ABSTRACT FROM AUTHOR]

ABSTRACT A poly(methyl methacrylate)- block-poly(4-vinylpyridine)- block-polystyrene (PMMA- b-P4VP- b-PS) triblock terpolymer is synthesized by ATRP to study its self-assembly with PAA in organic solvents. The self-assembly behavior of this system is compared with the one of a mixture of two diblocks, namely polystyrene- block-poly(4-vinylpyridine) (PS -b-P4VP) and poly(methyl methacrylate)- block-poly(methacrylic acid) (PMMA -b-PMAA). For both systems, formation of hydrogen-bonded complexes between the P4VP and PMAA or PAA blocks occurs. These complexes become insoluble in the solvent used and micelles with a P4VP/P(M)AA complexes core surrounded by PS and PMMA coronal chains are obtained in both cases. These micelles are analyzed by DLS and TEM. Spherical micelles are formed for both systems but the hydrodynamic radii obtained for the two types of micelles are different. Indeed, the micelles formed by the PMMA- b-P4VP- b-PS + PAA system are smaller than those observed for the PS -b-P4VP + PMMA -b-PMAA system. Finally, the effect of the molar ratio of the P4VP/PMAA complexing blocks is investigated. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 459-467 [ABSTRACT FROM AUTHOR]

The synthesis of triblock copolymers based on polysarcosine, poly- N-ε- t-butyloxycarbonyl- l-lysine, and poly- N-ε- t-trifluoroacetyl- l-lysine by ring-opening polymerization of the corresponding α-amino acid N-carboxyanhydrides (NCAs) is described. For the synthesis of N-ε- t-butyloxycarbonyl- l-lysine (lysine(Boc)) NCAs, an acid-free method using trimethylsilylchloride/triethylamine as hydrochloric acid (HCl) scavengers is presented. This approach enables the synthesis of lysine(Boc) NCA of high purity (melting point 138.3 °C) in high yields. For triblock copolypept(o)ides, the degree of polymerization (Xn) of the polysarcosine block is varied between 200 and 600; poly- N-ε- t-butyloxycarbonyl- l-lysine and poly- N-ε- t-trifluoroacetyl- l-lysine blocks are designed to have a Xn in the range of 10-50. The polypeptide-polypeptoid hybrids (polypept(o)ides) can be synthesized with precise control of molecular weight, high end group integrity, and dispersities indices between 1.1 and 1.2. But more important, the use of tert-butyloxycarbonyl- and trifluoroacetyl-protecting groups allows the selective, orthogonal deprotection of both blocks, which enables further postpolymerization modification reactions in a block-selective manner. Therefore, the presented synthetic approach provides a versatile pathway to triblock copolypept(o)ides, in which functionalities can be separated in specific blocks. [ABSTRACT FROM AUTHOR]

ABSTRACT Nitrile oxide 1,3 dipolar cycloaddition is a simple and powerful coupling methodology. However, the self-dimerization of nitrile oxides has prevented the widespread use of this strategy for macromolecular coupling. By combining an in situ nitrile oxide generation with a highly reactive activated dipolarophile, we have overcome these obstacles and present a metal-free macromolecular coupling strategy for the modular synthesis of several ABA triblock copolymers. Nitrile oxides were generated in situ from chloroxime terminated poly(dimethylsiloxane) B-blocks and coupled with several distinct hydrophilic (poly(2-methyloxazoline) and poly(ethylene glycol)), and poly( N-isopropylacrylamide) or hydrophobic (poly( l-lactide) A-blocks terminated in activated dipolarophiles in a rapid fashion with high yield. This methodology overcomes many drawbacks of previously reported metal-free methods due to its rapid kinetics, versatility, scalability, and ease of introduction of necessary functionality. Nitrile oxide cycloaddition should find use as an attractive macromolecular coupling strategy for the synthesis of biocompatible polymeric nanostructures. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 3134-3141 [ABSTRACT FROM AUTHOR]

ABSTRACT The morphology transition of binary mixtures of polystyrene-block-poly(butadiene)-block-poly(2-vinylpyridine)(SBV) triblock and polystyrene (PS) homopolymer thin films was investigated as a function of the volume fraction of added homopolymer and the annealing time in benzene vapor. It was found that the weight ratio of PS in the blends influenced the transition process. When PS content was >5%, the order-order transition (OOT) of core-shell cylinders (C) →sphere in 'diblock Gyroid' (sdG) → sphere in lamella (sL) → sphere (S) was observed, which was similar to ABC triblock copolymer except for the increased surface area of the PS phase. When PS content reached to 10-30%, the OOT in the sequence of C → sL → S was observed. The disappearance of the Gyroid phase is due to the change of the effective volume fraction. Further increasing the PS content, C phase also disappeared and sL → S was expected to take place. © 2014 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2014, 52, 1030-1036 [ABSTRACT FROM AUTHOR]