Types Of Copolymers Research Articles

The first application of isoindigo-based polymers in non-fullerene organic solar cells

Although isoindigo (IID)-based polymers can realize high charge mobility, these materials are currently confined to fullerene-based organic solar cells (OSCs). Herein, we designed a pair of alternative D-π-A type copolymers, PE71 and PE72, to expand the application in non-fullerene OSCs, where benzo[1,2-b:4,5-b′]thiophene (BDT), thieno[3,2-b]thiophene (TT) and IID units were used as D, A and π-bridge, respectively. The aim of optimizing the length of alkyl chains on TT bridge is to ensure polymer solubility, crystallinity as well as miscibility with acceptor molecules. We find that PE71 and PE72 exhibit similar optical and electronic properties, but PE71 with shorter hexyl chain tends to aggregate into fiber-like structure. In the end, Y6 is selected as the electron acceptor because of suitable energy levels and complementary absorption spectrum. Finally, PE71:Y6 device realizes a power conversion efficiency (PCE) of 12.03%, which is obviously higher than that of PE72:Y6 device (9.74%) and is also the highest value for IID-based photovoltaic polymers. The charge transport, molecular aggregation, film morphology and energy loss analysis were systematically investigated. The improved photovoltaic performance of PE71:Y6 mainly originates from the better interpenetrating network structure toward facilitating exciton seperation and free charge carrier transportation. Our results indicate that IID-based D-π-A polymers can also be utilized in non-fullerene OSCs and the alkyl chains on the thieno [3,2-b]thiophene π-bridge have a vital effect on the photovoltaic performance.

Synthesis and properties of a betaine type copolymer filtrate reducer

With the exploitation of ultra-high temperature deep wells, the fluid loss reducer as the core treatment agent of drilling fluid, in addition to ensuring the fluid loss performance, it needs to have both high temperature and high salt resistance and certain inhibition. Thus, N-(3-dimethylallyl)methacrylamide and 1,3-propane sultone were used to synthesize a betaine-type zwitterionic functional monomer named DMAPMAS. A zwitterionic copolymer PADAN as a fluid loss reducer for drilling fluids was prepared by attaching 2-acrylamide-2-methylpropanesulfonic acid, N-vinylpyrrolidone and synthetic DMAPMAS to the main chain of acrylamide via aqueous solution free radical polymerization. It not only has great thermal but has good fluid loss and inhibition performance. In addition, the addition of PADAN can effectively improve the particle size distribution of the drilling fluid system. The combination of PADAN and sulfonated polymer SMC, SMP-II and SPNH has the effect of reducing the fluid loss of drilling fluid. Moreover, it has good adaptability to a variety of drilling fluid systems. Applied to the sulfonation drilling fluid system and the polysulfide KCl drilling fluid system, it has the significant effect in fluid loss reduction and less impact on the rheological properties to adapt to various drilling fluid systems.

Synthesis of isoprene-based triblock copolymers by nitroxide-mediated polymerization

The nitroxide-mediated polymerization (NMP) of isoprene (I) initiated by the poly(ethylene-stat-butylene)-(SG1)2 dialkoxyamine (PEB-(SG1)2) at 115 °C in 50 vol% pyridine led to cis-1,4-rich poly(isoprene)s (PIs), exhibiting Mn,GPC = 52–59 K (PI equivalents) and Ð = 1.46–1.59. S-I-S triblock copolymers (S = styrene, Mn,GPC = 95–109 K, Ð = 2.11–2.29, FS = 0.30–0.49) were synthesized via subsequent S chain-extensions in bulk at 115 °C from these PI-(SG1)2 macro-initiators. A micro-phase separation, exhibiting possibly a cylindrical or lamellar morphology, was observed by atomic force microscopy for an S-I-S having FS = 0.30. Tensile strength at break σB = 2.8–4.1 MPa and elongation at break εB ~ 375–450% were measured for S-I-S samples with FS = 0.30–0.38. The substitution of the PS outer segments by more rigid segments rich in isobornyl methacrylate (IBOMA) units allowed to improve the stress–strain properties, with σB = 11.4 ± 0.6 MPa and εB = 1356 ± 214%. This IBOMA-I-IBOMA type copolymer also displayed an upper service temperature greater than 150 °C.

Block copolymer directed self-assembly defect modes induced by localized errors in chemoepitaxial guiding underlayers: A molecular simulation study

Block copolymer (BCP) directed self-assembly (DSA) has been presented as a potential economically attractive enhancement to extend the capabilities of optical lithography for semiconductor manufacturing. One concern in DSA is the level of defectivity that can be achieved in such a process. Although entropic effects will always lead to some degree of defectivity, highly ordered structures with a low theoretical equilibrium defect density can be produced by guiding the ordering and placement of the BCP domains using a patterned underlayer. Recent experimental studies have shown that while DSA processes can significantly reduce the observed defect density, defectivity levels are generally still higher than allowable for high-volume manufacturing and higher than what would be anticipated from free energy estimates of the observed defect modes. In particular, bridge defects are one of the most commonly observed defect modes in experimental DSA studies. A number of hypotheses have been proposed to explain the origins of these defects. One hypothesis is that so-called affinity defects present in the underlayer can spawn bridge defects in the overlying BCP film. The goal of the work reported here was to investigate the extent to which bridge defects can be generated or further reinforced in lamellae-forming block copolymer films due to affinity defects in the underlayer pattern. Coarse-grained molecular dynamics simulations were used to simulate the chemoepitaxial DSA of monodisperse block copolymer films atop underlayers with varying affinity defect sizes. Affinity defects were simulated by creating circular regions of a single polymer block type (which is the opposite block type of that used to pattern the underlayer guiding stripes) in the nominally neutral background region of the underlayer. These affinity defects were positioned in regions of the underlayer where they were the incorrect type to match the overlying block copolymer pattern. It was observed that the presence of an affinity defect in the neutral region of the underlayer caused the energetically preferential polymer block to wet the affinity defect, thus creating the nucleus of what could potentially become a bridge defect—even when the affinity defects were very small. As the radius of the underlayer affinity defect (RoD) increased, the amount of block copolymer of incorrect type (with respect to a perfectly assembled copolymer pattern) that assembled above the affinity defect increased; but, in general, the thickness of the wetting layer in contact with the affinity defect was only roughly one polymer chain thick. These data suggest that an affinity defect in the underlayer alone is unlikely to be noticeably enhanced by significant bridge defect formation in a monodisperse block copolymer film.

Highly Efficient Microscopic Charge Transport within Crystalline Domains in a Furan‐Flanked Diketopyrrolopyrrole‐Based Conjugated Copolymer

AbstractElucidating the interrelation between the molecular structure and charge transport properties in conjugated polymer thin films is an essential issue in developing the design principle of high‐performance polymer materials for application in organic electronics. In particular, the backbone planarity is suggested to be a key element that governs the transport performance, especially in recently developed donor–acceptor (D–A)‐type copolymers exhibiting high mobility, whereas the direct evaluation of the intrinsic transport performance, usually realized only within the small crystalline domains, is difficult by using conventional macroscopic measurements. Here, it is demonstrated that a D–A type copolymer, PDPPF‐DTT, which consists of furan‐flanked diketopyrrolopyrrole (DPP) and dithienothiophene (DTT) units in the conjugated backbone, exhibits a highly efficient charge transport performance within the crystalline domains with a remarkably low activation energy of less than 8 meV, based on microscopic measurements using field‐induced electron spin resonance spectroscopy. This high transport performance is primarily caused by the high backbone planarity realized by introducing furan‐flanked DPP and fused dithienothiophene units, which is demonstrated from the density functional theory calculations. This result provides a microscopic indication of the effectiveness of the present molecular design to produce a planar backbone and realize highly efficient charge transport performance.

A Global View on Block Copolymers.

In this systematic review, a total of 45,143 publications on block copolymers, issued between 1952 and 2019, are analyzed in terms of number, source, language, institution, country, keywords, and block copolymer type, to find out their evolution and predict research trends. The number of publications devoted to block copolymers has been growing for over six decades, maintaining a consistent level throughout the last few years. In their majority, documents came out of the United States, although more recently, Chinese institutions are those displaying the largest production. Keywords analysis indicated that one-third of the publications concerned synthesis, around 20% explored self-assembly and morphological aspects, and another 20% referred to block copolymer applications in solution. In particular, 2019 confirmed the expansion of studies related to drug delivery, and in minor extent, to a deeper view of self-assembling. Styrene–butadiene–styrene block copolymer was the most popular in studies covering both basic and industrially oriented aspects. Other highly investigated copolymers are PEO-b–PPO-b–PEO (Pluronic©) and amphiphilic block copolymers based on polycaprolactone or poly(lactic acid), which owed their success to their potential as delivery vehicles. Future trending topics will concern nanomedicine challenges and technology-related applications, with a special attention toward the orientation and ordering of mesophase-separated morphologies.

Effects of aggregate type and SBS copolymer on the interfacial heat transport ability of asphalt mixture using molecular dynamics simulation

The interface between the asphalt and the aggregate contributes significantly to the thermal performance of asphalt mixture. This paper employs non-equilibrium molecular dynamics simulations utilizing the Langevin method, and reveals the interfacial heat transport of asphalt mixture. Kapitza thermal resistance is applied as the assessment index of interfacial thermal properties. The effects of styrene–butadienestyrene (SBS) copolymers and chemical components of aggregates on the interfacial heat transport ability are investigated respectively. The Kapitza resistance of silica-virgin asphalt system decreases with the increase of temperature, while the values of calcium carbonate-virgin asphalt system have a slightly fluctuation with temperatures, which shows a better thermal stability of asphalt mixture with calcium carbonate aggregates. In addition, the interfacial heat transport ability is improved significantly with the addition of SBS molecules, and the linear structure of SBS molecules has a better effects than radial structure. Furthermore, compared with 7.9 wt% SBS, higher content of SBS (20 wt%) hardly further reduces the Kapitza resistance value. The research findings can provide insights to better understand the interfacial heat transport ability of asphalt mixture.

The Effect of Nano Materials on Lost Circulation Control of Azkand Formation in Khabaz Oil Field

Experimental tests were carried to control lost circulation in the Khabaz oil field using different types of LCMs including Nano-materials. A closed-loop circulation system was built to simulate the process of lost circulation into formations. Two dolomite plugs were used from different depths of the formation of Azkand in Khabaz oil field. The experimentations were carried out to study the effect of different types of LCMs, cross-linked copolymer (FLOSORB CE 300 S), SiO2 NP, and Fe2O3 NP, on mud volume losses as a function of time.
 The rheological measurements of the nanoparticles-reference mud system showed that both of the SiO2 NP and Fe2O3 NP worked best at 1.2 g/l. and the closed-loop circulation system showed that SiO2 NP cured losses by 48.3% and 37.5% for core plugs 5C1 and 1C2 respectively which is better than Fe2O3 NP loss curing which was 37.9% and 31.3% for core plugs 5C1 and 1C2 respectively.
 On the other hand, FLOSORB CE 300 S- Fe2O3 NP-reference mud systems cured losses up to 69% with 0.25g/l FLOSORB CE 300 S and 79.3% with 0.5 g/l FLOSORB CE 300 S which is better than the FLOSORB CE 300 S- SiO2 NP-reference mud systems results.

Structure formation of a temporarily plasticized matrix of polymer composite materials with adjustable deformability for transformable structures

It is established that with the selected type and composition of the amino-epoxy copolymer, which is equilibrium swollen in the anhydride-epoxy temporary plasticizer, the decisive role in ensuring the initial elasticity and final deformation heat resistance of such systems plays the formation of the initial polymer network of the primary polymer, which, when combined with a temporary modifier, provides of a minimum low T g . The additional formation of the network structure of the primary polymer and the network interpenetrating with it, which is formed during the curing of the temporary plasticizer, provides the required T g of the cured composition as a whole, proportional to the mass fraction of components and the density of the networks. The processes of macrophase separation during curing of a temporary plasticizer and, accordingly, the regulation of the phase morphology of the cured compositions are limited by the formed network of the initial polymer.

Function Synergy of Cross-Linked Cationic PVA Polymer to AMPS-Type Fluid Loss Additive Used for Cement-Based Material

In this research, a kind of 2-acrylamido-2-methylpropanesulfonic acid sodium salt- (AMPS-Na-) type copolymer additive, the fluid loss additive (FLA), named as FLA A additive, was used for research. The performance of FLA A was tested and found to fail in the effective control of free water and to hinder the hydration process for delaying the breaking of the early hydration shell. The reason for it was the absorbed behavior and chelating effect of the AMPS-Na unit to Ca2+ hydrating cement particles. Thus, a cationic polyvinyl alcohol (PVA) polymer, modified by glyoxal and boric acid, was discovered due to its excellence in associating with the FLA A additive for controlling the free cement-based material water amount and preventing the chelating effect of FLA A chains on the surface of the cement-based material. Glyoxal/boric acid-modified polyvinyl alcohol, abbreviated as PVAGB or PVA-G-B, was with special molecular properties, i.e., positive ZETA (ζ) potential characteristics and cross-linked molecular structure. Due to competitive absorbed behavior of glyoxal-modified hydroxyl groups and free Ca2+ released by the hydration product, the chelating effect of AMPS-Na units to Ca2+ was weakened and the possibility of FLA A chains being absorbed to the surface of the cement-based material was decreased. Then, the formation of a complete fluid loss system was obtained; i.e., the fluid loss volume decreased to less than 50 mL at 30°C and 108 mL at 80°C with 0.2 percentage by weight of cement (%BWOC) of PVAGB and 0.50%BWOC (percentage by weight of cement) of FLA A. Besides, the hydration process of cement-based material was accelerated due to formation of more C-S-H gels in the early hydration period. As a result, the cement-based material not only showed no worse compressive-strength retrogression but also showed a stable 28-day compressive strength of 28 MPa.

Synthesis, characterization and applications of copolymer of β – cyclodextrin: a review

Herein, this review the synthesis of different types of copolymer of β-cyclodextrin (β-CD) by different functional monomers and cross-linkers is discussed. β-CD shows good inclusion property, surface area, porous structure and unique host-guest properties. CDs, the macrocyclic compounds are renowned for their inclusion ability. Several chemical and polymerized derivatives of parent CDs are synthesized to improve the physicochemical/biopharmaceutical properties of drug and inclusion capacity of CD. The future panorama of polymerized CDs is quite bright as they can serve as useful multifunctional tools for pharmaceutical scientists to develop and optimize drug delivery through various routes and in fabrication of biosensors. For drug delivery, the efficacy of monomer is made suitable and the well-known inclusion ability of β-CD is retrospected. The synthesized copolymer of β-CD is characterized via several microscopic and spectroscopic techniques such as synchrotron radiation based PXRD, TGA (thermogravimetric analysis), DSC and FTIR. The aim of this review paper is to study different methods of synthesis of copolymers of β-CD by different functional monomers and cross-linkers. The review suggests methods and conditions used for the optimized synthesis of copolymers of β-CD. Further, the application of β-CD in the field of tissue engineering, packing material, drug delivery, cosmetics, personal care and toiletry, waste management, catalysis adhesive and coating industry have also been discussed here.

Enhancement the photovoltaic performance of conjugated polymer based on simple head-to-head alkylthio side chains engineered bithiophene

In this article, three novel and simple molecular structure with donor-acceptor (D-A) type copolymers via only head-to-head alkoxy (OR) and/or alkylthio (SR) side chains onto the bithiophene (BT) as donor units and fluorinated benzotriazole (FBTA) as acceptor unit, namely, PBTOR-FBTA, PBTOSR-FBTA and PBTSR-FBTA, were successfully designed and synthesized. The impacts of sulfur-oxygen (S⋯O) or sulfur-sulfur (S⋯S) noncovalent interactions on their physicochemical properties, molecular stacking, carrier mobility, morphologies of blend films, as well as their photovoltaic performance were deeply and systematically studied. The introduction of SR side-chains suddenly lowered the highest occupied molecular orbital (HOMO) energy levels, blue-shifted absorption, enhanced π-π stacking, as well as improved morphology of the photoactive layer blends in comparison with the reference polymer without SR side-chain. Polymer solar cells (PSCs) were fabricated to estimate their photovoltaic performance of the polymers. Under an optimized blend ratio of PBTSR-FBTA:PC71BM (1:0.8, w/w), the PBTSR-FBTA-based device exhibits a higher power conversion efficiency (PCE) of 6.25%, which is about 3.34 and 1.87 folds than that of the PBTOR-FBTA and PBTOSR-FBTA-based devices, respectively. Our research results demonstrate that the modification of the simple and low-cost SR side chains is an effective strategy to improve the photovoltaic performance of the polymers.

Enhanced Heat Resistance and Adhesive Strength of Styrene-Acrylic Triblock Copolymer Elastomers by Incorporating Acrylic Acid.

Herein, we present an industrially applicable strategy to enhance the heat resistance and adhesive properties of ABA triblock copolymer-based elastomers composed of styrene (St) and n-butyl acrylate (nBA) by incorporating acrylic acid (AA) at different segments. Three types of triblock copolymers, namely, poly(St-r-AA)-b-poly(nBA)-b-poly(St-r-AA), poly(St)-b-poly(nBA-r-AA)-b-poly(St), and poly(St)-b-poly(nBA)-b-poly(St), were synthesized by reversible addition–fragmentation chain-transfer (RAFT) polymerization. Large-scale RAFT polymerization afforded industrially applicable AA-containing triblock copolymers with moderate molecular weights and predetermined comonomer compositions (St/nBA/AA = 15/83/2–24/73/3, number-average molecular weight (Mn) = 30,000–110,000, and resulting product > 200 g). The heat resistance and pressure-sensitive adhesive properties of the triblock copolymers were evaluated. Among them, poly(St-r-AA)-b-poly(nBA)-b-poly(St-r-AA), having poly(nBA) as the middle soft segment and poly(St-r-AA) as hard segments at both ends, exhibited excellent heat creep resistance and increased adhesiveness to stainless steel. The feasibility to manipulate the heat resistance and adhesive properties by incorporating AA units into hard and soft segments, in addition to the ease of operation, high block efficiency, and metal-free nature owing to the RAFT process, is highly beneficial for practical applications of these copolymers.

The impact of [1,2,5]chalcogenazolo[3,4‐f]‐benzo[1,2,3]triazole structure on the optoelectronic properties of conjugated polymers

AbstractTwo novel conjugated near‐infrared (NIR) absorbing donor–acceptor type copolymers comprising benzodithiophene as the donor and [1,2,5]chalcogenazolo[3,4‐f]‐benzo[1,2,3]triazole derivatives as the acceptors, spaced with thiophene as the π‐bridge, were designed and synthesized via Stille polycondensation reaction. The effect of acceptor strength on optoelectronic properties was targeted and investigated. Branched alkyl chains (the extended 2‐octyl‐1‐dodecyl alkyl chain; C8C12) were introduced to 5H‐[1,2,3]triazolo[4′,5′:4,5]benzo[1,2‐c][1,2,5]thiadiazole and 5H‐[1,2,3]triazolo[4′,5′:4,5]benzo[1,2‐c][1,2,5]selenadiazole for enhanced solubility of polymers which ease the processability hence device constructions. The strongly electron‐withdrawing units lead to a substantial change in the absorption properties via promotion of the intramolecular charge transfer band alongside the π–π* transition. The resultant soluble polymers were characterized via cyclic voltammetry to determine highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels as −5.00 and −3.92 eV for PSBT and −4.86 and −4.04 eV for PSeBT, respectively. Electronic band gaps of the copolymers were calculated as 1.08 eV for PSBT and 0.82 eV for PSeBT, respectively. NIR absorbing copolymers were used to construct electrochromic devices.

Precise synthesis of poly(IBVE-co-HBVE) with tunable thermo-response via fast flow polymerization

A new type of thermosensitive copolymers composed of isobutyl vinyl ether (IBVE) units and 4-hydroxybutyl vinyl ether (HBVE) units were synthesized within 4.34 s in a microflow platform. The synthesis started from the living cationic copolymerization of IBVE and 4-(tert-butyldimethylsilyloxy) butyl vinyl ether (BMS-Bu) using cationogen/SnCl4 initiation system in the presence of an added base, resulting in a copolymer with a narrow dispersity. This new platform enabled very low concentrations of added base (0.1 M) and offered highly controllability on fast living cationic copolymerization, making it possible to determine the reactivity ratio of IBVE and BMS-Bu at low-conversion within 0.15 s. Subsequently, after desilylation, poly(IBVE-co-HBVE) with narrow dispersity (Mw/Mn ≈ 1.10) was obtained, presenting strictly controllable LCST behavior. Particularly, the phase transition experienced sharp and almost reversible process, and Tps can be tuned from 22.5 to 38.5 °C by changing the ratio of two monomers in feeding.

Mechanical performance of adhesive joints using high-performance nanocomposite adhesive material with carbon nanotube and triblock copolymer hybrids

This research investigates the mechanical performance of adhesive joints using high-performance epoxy (EP) based nanocomposite adhesive materials modified by ozone functionalized carbon nanotubes (OZ-CNTs) and two types of triblock copolymers (BCPs) including Methylmethacrylate-Butylacrylate-Methylmethacrylate (MAM) and Styrene-Butadiene-Methylmethacrylate (SBM). Different mechanical tests such as double-lap shear, tensile-butt, and Mode I long-crack extension tests were conducted to evaluate the effect of the BCP and OZ-CNT modification on the mechanical performance of the epoxy adhesive material. From the double-lap shear test, the strength of the 0.5 wt% OZ-CNT + SBM hybrid epoxy adhesive joint achieved a 112% increase compared to that of the unmodified epoxy. The ultimate plastic shear strain of the modified adhesives was significantly increased by 100% for the 0.5 wt% OZ-CNT + SBM/EP, representing a significant improvement in strain energy density and superior resistance to failure for any joints that would be applied in practice. However, the tensile-butt joint strength of the BCP/EP and OZ-CNT + BCP/EP joints was slightly lower than that of the unmodified epoxy, which was due to the presence of the lower strength and stiffness nanophase BCPs. The long-crack extension studies revealed a very large increase of Mode I fracture toughness of 1190% for the nano-modified hybrid joints with 0.5 wt% OZ-CNT + SBM/EP, showing that the OZ-CNT addition greatly enhances the fracture toughening processes provided by the SBM. It was also found that the addition of OZ-CNTs increased the electrical conductivity by 4 orders of magnitude compared with the unmodified and BCP modified epoxy. Rheological studies were also carried out to study the change in viscosity of the epoxy with the addition of BCPs and OZ-CNTs. The viscosity of the epoxy was increased with the addition of BCP or OZ-CNTs and the viscoplastic behaviour was observed for the hybrid OZ-CNT and BCP/EP adhesives, which was analysed using Casson's model.

Conversion of an Injectable MMP-Degradable Hydrogel into Core-Cross-Linked Micelles.

In this study, a new type of injectable hydrogel called “HyMic” that can convert into core cross-linked (CCL) micelles upon exposure to matrix metalloproteinases (MMP’s), was designed and developed for drug delivery applications. HyMic is composed of CCL micelles connected via an enzyme cleavable linker. To this end, two complementary ABA block copolymers with polyethylene glycol (PEG) as B block were synthesized using atom transfer radical polymerization (ATRP). The A blocks were composed of a random copolymer of N-isopropylacrylamide (NIPAM) and either N-(2-hydroxypropyl)methacrylamide-cysteine (HPMA-Cys) or N-(2-hydroxypropyl) methacrylamide-ethylthioglycolate succinic acid (HPMA-ETSA). Mixing the aqueous solutions of the obtained polymers and rising the temperature above the cloud point of the PNIPAM block resulted in the self-assembly of these polymers into flower-like micelles composed of a hydrophilic PEG shell and hydrophobic core. The micellar core was cross-linked by native chemical ligation between the cysteine (in HPMA-Cys) and thioester (in HPMA-ETSA) functionalities. A slight excess of thioester to cysteine groups (molar ratio 3:2) was used to allow further chemical reactions exploiting the unreacted thioester groups. The obtained micelles displayed a Z-average diameter of 80 ± 1 nm (PDI 0.1), and ζ-potential of −4.2 ± 0.4 mV and were linked using two types of pentablock copolymers of P(NIPAM-co-HPMA-Cys)-PEG-peptide-PEG-P(NIPAM-co-HPMA-Cys) (Pep-NC) to yield hydrogels. The pentablock copolymers were synthesized using a PEG-peptide-PEG ATRP macroinitiator and the peptide midblock (lysine-glycine-proline-glutamine-isoleucine-phenylalanine-glycine-glutamine-lysine (Lys-Gly-Pro-Gln-Gly-Ile-Phe-Gly-Gln-Lys)) consisted of either l- or d-amino acids (l-Pep-NC or d-Pep-NC), of which the l-amino acid sequence is a substrate for matrix metalloproteases 2 and 9 (MMPs 2 and 9). Upon mixing of the CCL micelles and the linker (l/d-Pep-NC), the cysteine functionalities of the l/d-Pep-NC reacted with remaining thioester moieties in the micellar core via native chemical ligation yielding a hydrogel within 160 min as demonstrated by rheological measurements. As anticipated, the gel cross-linked with l-Pep-NC was degraded in 7–45 days upon exposure to metalloproteases in a concentration-dependent manner, while the gel cross-linked with the d-Pep-NC remained intact even after 2 months. Dynamic light scattering analysis of the release medium revealed the presence of nanoparticles with a Z-average diameter of ∼120 nm (PDI < 0.3) and ζ-potential of ∼−3 mV, indicating release of core cross-linked micelles upon HyMic exposure to metalloproteases. An in vitro study demonstrated that the released CCL micelles were taken up by HeLa cells. Therefore, HyMic as an injectable and enzyme degradable hydrogel displaying controlled and on-demand release of CCL micelles has potential for intracellular drug delivery in tissues with upregulation of MMPs, for example, in cancer tissues.

Translating the fabrication of protein-loaded poly(lactic-co-glycolic acid) nanoparticles from bench to scale-independent production using microfluidics

In the formulation of nanoparticles, poly(lactic-co-glycolic acid) (PLGA) is commonly employed due to its Food and Drug Administration and European Medicines Agency approval for human use, its ability to encapsulate a variety of moieties, its biocompatibility and biodegradability and its ability to offer a range of controlled release profiles. Common methods for the production of PLGA particles often adopt harsh solvents, surfactants/stabilisers and in general are multi-step and time-consuming processes. This limits the translation of these drug delivery systems from bench to bedside. To address this, we have applied microfluidic processes to develop a scale-independent platform for the manufacture, purification and monitoring of nanoparticles. Thereby, the influence of various microfluidic parameters on the physicochemical characteristics of the empty and the protein-loaded PLGA particles was evaluated in combination with the copolymer employed (PLGA 85:15, 75:25 or 50:50) and the type of protein loaded. Using this rapid production process, emulsifying/stabilising agents (such as polyvinyl alcohol) are not required. We also incorporate in-line purification systems and at-line particle size monitoring. Our results demonstrate the microfluidic control parameters that can be adopted to control particle size and the impact of PLGA copolymer type on the characteristics of the produced particles. With these nanoparticles, protein encapsulation efficiency varies from 8 to 50% and is controlled by the copolymer of choice and the production parameters employed; higher flow rates, combined with medium flow rate ratios (3:1), should be adopted to promote higher protein loading (% wt/wt). In conclusion, herein, we outline the process controls for the fabrication of PLGA polymeric nanoparticles incorporating proteins in a rapid and scalable manufacturing process.Scale-independent production of polymer nanoparticles

Effect of triblock copolymers on crystal growth and the photocatalytic activity of anatase TiO2 single crystals.

In order to evaluate the effect of a triblock copolymer on the growth of TiO2 crystals, anatase TiO2 crystals with different morphologies and structures were synthesized by controlling the content and type of triblock copolymer in the solvothermal route. The resulting samples were characterized by XRD, XPS, SEM, TEM and EDX. The characterization results show that hydrofluoric acid can promote the formation of highly active (001) facets by the formation of a Ti–F bond. The triblock copolymers (P123 and F127) refine the surface structure of polycrystalline spherical TiO2 and make the crystal surface homogeneous and smooth. Moreover, P123 causes the agglomeration effect and hinders the recrystallization process of anatase TiO2 single crystals, and this will lead to corrosion of the crystal facets. Meanwhile, F127 destroys crystal formation and hinders crystal growth due to its special micelle structure. In addition, research on the photocatalytic activity proposed that the integrity of the (001) and (101) facets was a critical factor in the photocatalytic reaction. The resultant anatase TiO2 single crystals could produce more hydroxyl radicals (˙OH) in the photocatalytic system, which exhibited remarkable photocatalytic performance for the degradation of three types of dye.

Improvement of mechanical properties of in situ-prepared HTPE binder in propellants.

A new type of hydroxyl-terminal block copolymer (HTPE) binder with excellent mechanical properties was prepared using an in situ preparation method. Compared with traditional HTPE binder preparation, this method involves relatively simple operations, which not only reduces costs, but also does not require a complicated synthesis process to prepare the HTPE prepolymer intermediate. Thus, it is expected to replace the binder for HTPE propellants. The mechanical properties, crosslinking density, hydrogen bonding, and thermal performances of the prepared HTPE binders were investigated through tensile testing, low-field nuclear magnetic resonance (LF-NMR), Fourier-transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC) analysis. The ultimate tensile strength (σm) of the in situ-prepared HTPE binder was 1.83 MPa, the fracture elongation (εb) was 371.61%, and the strength increased by 80% compared to the HTPE binders. The crosslink density (Ve) decreased with an increasing content of PEG and/or TDI. The proportion of H-bonds formed by the imino groups increased with the content of PEG and TDI and reached 81.49% at PEG and TDI contents of 50% and 80%, respectively, indicating a positive correlation between the H-bonds and σm. Based on the statistical theory of elasticity, the integrity of the curing networks showed that the contents of PEG and TDI affected the integrity of the curing networks. The DSC data of the in situ-prepared HTPE binder showed a lower glass transition temperature. Finally, compared to HTPE propellant, the strength and elongation of the in situ-prepared HTPE propellant increased by 206% and 135%, respectively. This exciting result greatly enhances the feasibility of the in situ HTPE preparation method.