Random Copolymer Poly Research Articles

Dual Thermo- and Photo-Responsive Micelles Based on Azobenzene-Containing Random Copolymer.

Amphiphilic random copolymer poly(methacrylamido-azobenzene)-ran-poly(2-hydroxyethylacrylate) (PMAAAB-ran-PHEA) was synthesized via hydrolysis of poly(methacrylamido-azobenzene)-ran-poly[2-((2′-tetrahydropyranyl)oxy)ethylacrylate] (PMAAAB-ran-P(THP-HEA)), which was prepared by conventional radical polymerization. PMAAAB-ran-PHEA micelles were then prepared via dialysis method against water with DMF as solvent. The structure, morphology, size, and low critical solution temperature (LCST) of PMAAAB-ran-PHEA and its micelles were determined by 1H-NMR, GPC, TEM, and DLS. The thermo- and photo-responsive behaviors of the resulting polymer micelles were investigated with Nile red as a fluorescence probe. The results showed that PMAAAB-ran-PHEA micelles were porous or bowl-shaped and its size was 135–150 nm, and its LCST was 55 °C when FMAAAB of the random copolymer was 0.5351; the hydrophobicity of the micellar core was changed reversibly under the irradiation of UV light and visible light without release of Nile red or disruption of micelles; the size and solubilization capacity of the micelles were dependent on temperature, and Nile red would migrate for many times between the water phase and the micelles, and finally increasingly accumulated during the repeated heating and cooling processes.

Poly(lactic acid-co-glycolic acid-co-ε-caprolactone)의 합성, 분석 및 감압 접착 특성

Random copolymers of poly(lactic acid-co-glycolic acid-co-ε-caprolactone) (PLGA-CL) based on lactic acid (LA), glycolic acid (GA), citric acid (CA), and ε-caprolactone (CL) were synthesized and characterized. ¹H NMR spectra showed that the polymerization conversion of various monomers was high under the experimental conditions, and the degree of polymerization of the polycaprolactone (PCL) segment increased with the growth of CL content. The content of CL has a remarkable effect on the decrease of glass transition temperature (T<SUB>g</SUB>) of the copolymers. The adhesive properties of random copolymers as pressure-sensitive adhesive (PSA) were evaluated. With the increase of CL content, 180° peel strength, the shear strength and loop tack decreased. When CL content was 16.7 wt%, 180° peel strength was 4.76 N/25 ㎜, and loop tack was 8.45 N/25 ㎜.

Poly (vinyl alcohol-co-ethylene) (EVOH) modified polymer inclusion membrane in heavy rare earths separation with advanced hydrophilicity and separation property

Efficient separation of adjacent rare earths is an interesting and challenging job for membrane separation scientists. In this article, a novel polymer inclusion membrane (PIM) incorporating the hydrophilic additive random copolymer poly (vinyl alcohol-co-ethylene) (EVOH) was synthesized. Due to the polarity of P = O and P-OH groups in Cyanex272 and hydrophilicity of –OH groups in EVOH, the membranes exhibited much smaller water contact angles than pure PVDF membranes. And FT-IR results indicated that the addition of EVOH made no difference on the coordination between P = O, P-OH in Cyanex272 and Lu3+. SEM and AFM results indicated that the addition of appropriate amount of EVOH could generate more and larger surface pores and internal channels. Optimum membrane compositions and permeation conditions were fixed via static adsorption and dynamics permeation experiments. Separation factor was calculated as high as 3.78, which was much higher than previous studies no matter in solvent extraction or membrane separation. It is worth noting that it’s the first time an obvious carrier’s leakage was observed via characterizations which implied Cyanex272 may be not a perfect carrier in terms of PIM’s stability. All these results proved that this novel PIM with EVOH serving as hydrophilic additive could be further testified in heavy rare earths separation and purification process.

Ionic Transport Properties of Cation-Exchange Membranes Prepared from Poly(vinyl alcohol-b-sodium Styrene Sulfonate).

Membrane resistance and permselectivity for counter-ions have important roles in determining the performance of cation-exchange membranes (CEMs). In this study, PVA-based polyanions—poly(vinyl alcohol-b-sodium styrene sulfonate)—were synthesized, changing the molar percentages CCEG of the cation-exchange groups with respect to the vinyl alcohol groups. From the block copolymer, poly(vinyl alcohol) (PVA)-based CEMs, hereafter called “B-CEMs”, were prepared by crosslinking the PVA chains with glutaraldehyde (GA) solution at various GA concentrations CGA. The ionic transport properties of the B-CEMs were compared with those previously reported for the CEMs prepared using a random copolymer—poly(vinyl alcohol-co-2-acrylamido-2-methylpropane sulfonic acid)—hereafter called ”R-CEMs”. The B-CEMs had lower water content than the R-CEMs at equal molar percentages of the cation-exchange groups. The charge density of the B-CEMs increased as CCEG increased, and reached a maximum value, which increased with increasing CGA. A maximum charge density of 1.47 mol/dm3 was obtained for a B-CEM with CCEG = 2.9 mol% and CGA = 0.10 vol.%, indicating that the B-CEM had almost two-thirds of the permselectivity of a commercial CEM (CMX: ASTOM Corp. Japan). The dynamic transport number and membrane resistance of a B-CEM with CCEG = 8.3 mol% and CGA = 0.10 vol.% were 0.99 and 1.6 Ωcm2, respectively. The B-CEM showed higher dynamic transport numbers than those of the R-CEMs with similar membrane resistances.

Facile technique to encapsulate phase change material in an amphiphilic polymeric matrix for thermal energy storage

A facile fabrication technique of producing novel porous microcapsules encapsulating n-Eicosane as phase change material (PCM) with a random copolymer of poly (methyl methacrylate0.9-co-2-hydroxyethyl methacrylate0.1) (poly(MMA0.9-co-HEMA0.1)) as shell material is being reported. The porous microparticles (particle size: 31.8 ± 9 µm; porosity: ~30 ± 13%) with a hollow core (shell thickness: 1.60 ± 0.2 µm) were obtained by adopting a synthetic pathway of hot water assisted double emulsion (water/oil/water) system. Strikingly, the microcapsule system was found to entrap > 95% n-Eicosane, thus achieving significantly high thermal energy storage capability (~95%). The porous microcapsules with a phase transition enthalpy of ~ 160 J/g exhibited high phase transfer repeatability and long durability. The non-isothermal and isothermal DSC study further revealed the heat charging and discharging conditions for the microcapsules. Moreover, in contrast to neat hydrophobic PCM, the porous particles with partially hydrophilic shell (owing to polyHEMA unit) displayed better water dispersibility along with efficient thermal management characteristic as revealed by Infrared thermography. Thus, the microencapsulated phase change material in porous microcapsules can be a smart combination of good thermal energy storage function with wettability. Potentially such microcapsules may be exploited as thermal energy storage materials for space conditioning in buildings because of the suitable phase transition temperature (37 °C) displayed by the selected PCM (n-Eicosane). Our study comprehensively demonstrated water dispersible porous polymeric particles with significantly high thermal energy storage (>95%) performance that was not reported till date.

Random copolymer of poly(polyethylene glycol methyl ether)methacrylate as tunable transition temperature solid-solid phase change material for thermal energy storage

Polymer based phase change materials (PCM) for thermal energy storage (TES) applications have gained some attention recently due to their high stability and potential solid to solid phase transition. Here, we are the first to utilize a simple copolymerization strategy for static tunability transition temperature (Tt) of polymeric PCM. The copolymerization between short and long side chain polyethylene glycol based methacrylate polymers was designed to tune Tt with minimum impact on their energy density. Polarized optical microscope and x-ray techniques were also used to understand the relationship between crystal structure and Tt of different copolymer composition which was discussed in the context. The solid to solid transition polymeric PCM were successfully developed with tunable Tt ranged from 18 °C to 35 °C which is suitable toward building envelop applications.

The Swelling and Transition Behavior of Thermo-Responsive Poly(2-(2-Methoxyethoxy) Ethoxyethyl Methacrylate-co-Poly(Ethylene Glycol) Methyl Ether Methacrylate) Thin Films

Thermo-responsive random copolymer poly (2-(2-methoxyethoxy) ethoxyethyl methacrylate-co-poly (ethylene glycol) methyl ether methacrylate), abbreviated as P(MEO2MA-co-OEGMA300) was synthesized by 2-(2-methoxyethoxy) ethoxyethyl methacrylate (MEO2MA) and poly (ethylene glycol) methyl ether methacrylate (OEGMA300) with a molar ratio of 1:1 via atom transfer radical polymerization (ATRP). The structure of P(MEO2MA-co-OEGMA300) was confirmed by 1H NMR and GPC. The transition behaviors of P(MEO2MA-co-OEGMA300) in aqueous solution were investigated by UV-Vis and DLS. While the transition behaviors of P(MEO2MA-co-OEGMA300) thin films were probed by white light interferometry. Compared to the P(MEO2MA-co-OEGMA300) in solution, it shows a much broader transition region, which is a promising candidate for the slow release of drug in the field of medicine.

Multiple-stimuli-responsiveness and conformational inversion of smart supramolecular nanoparticles assembled from spin labeled amphiphilic random copolymers

HypothesisOrganic radical polymers with tailored pendant functionalities have emerged as exciting and promising materials for their application versatility. Moreover, eco-friendly polymer-based organic nanomaterials with redox-active pendant side groups can replace the harmful heavy metal-based inorganic materials. On the other hand, self-assembled nanomaterials are of great interest and attracted more attention recently for their promising application in different advanced fields, but it is yet challenging to predict suitable hydrophilic-lipophilic balance (HLB) for stimuli-responsive random copolymers assembly due to structural irregularity. Among several experimental techniques, electron paramagnetic resonance (EPR) spectroscopy plays a unique and promising role in revealing structural and dynamic information of nanostructured radical containing materials. ExperimentsIn this study, a series of spin labeled amphiphilic random copolymers poly(methyl methacrylate-co-acrylic acid) have been synthesized and characterized by FT-IR, UV–Vis spectroscopies, TGA, DSC and water contact angle (CA) techniques. Their electrochemical properties have been determined by cyclic voltammetry (CV) in different organic solvents. EPR spectroscopy has been applied with other analytical techniques to elucidate the smart supramolecular nanoparticles (SNPs) formation, stimuli-responsiveness and structural changes through the dynamics of different molecular interactions. FindingsThe structural and dynamic information of self-assembled nanoparticles have been observed to be dependent on multiple-stimuli-responsiveness in different microenvironments by applying physiological and chemical parameters such as the different concentration of radicals, pH, temperature, nature of the solvent and reducing agent. The obtained results reveal the knowledge to understand insight into the mechanism for the formation of stimuli-responsive colloidal nanoparticles assembled from amphiphilic random copolymers with apt HLB value. The CV results reveal that the charge transfer process of the nanoparticles in solution was diffusion regulated and depended on the accessibility of radicals. The radical (spin labeled) polymers offer a broad way to develop stimuli-responsive materials in various colloidal nanostructures by changing the microenvironment, appreciating their potential advanced applications in electronic devices, catalysis, stimuli-triggered drug/gene delivery and reactive oxygen species (ROS) scavenger.

Study of the partition of sodium diclofenac and norfloxacin in aqueous two-phase systems based on copolymers and dextran

The partitioning behavior of norfloxacin (more hydrophilic) and sodium diclofenac (more hydrophobic) was studied considering the use of aqueous two-phase systems (ATPSs) based in copolymers and dextran. For this research, the phase behavior of systems composed of water, a copolymer (Pluronic PE6400, Pluronic L35, Pluronic PE6800, PEG-ran-PPG monobutyl ether and PEG-ran-PPG) and dextran (Mw=40000 and 6000 g.mol−1) were investigated. The phase diagrams showed that by increasing the molecular weight and the copolymer PPG/PEG ratio, the biphasic region is enlarged. After defining the bionodal curves, a preliminary screening on the partition of two pharmaceutic ingredients (sodium diclofenac and norfloxacin) was carried. After selected the most appropriate ATPS for the partition of both drugs, namely systems based on diblock copolymers (poly(ethylene glycol)-poly(propylene glycol)) – dextran T6 and one random copolymer (poly(ethylene glycol)-ran-poly(propylene glycol)) – dextran T6, the effect of the copolymer concentration and different mixture points was assessed. In the end, the results showed that by increasing the copolymer concentration and tie-line length, the partition coefficient of the pharmaceutical ingredients increased in the block copolymer-based ATPS and decreased in systems containing the random copolymer.

Rheological Behavior of a Quaternary Ammonium Copolymer in the Presence of Inorganic Salts

Quaternary ammonium random copolymers poly(methacryloyloxyethyl trimethyl ammonium chloride-co-acrylamide) P(DMC-AM) with either varied cationicities or intrinsic viscosities were synthesized and their structure was analyzed by FTIR and NMR; the results verified the structure of the P(DMC-AM). The rheological behavior of the P(DMC-AM) resulting from its polymer structure (cationicity and intrinsic viscosity) in NaCl aqueous solutions was studied. The results showed that increasing the polymer cationicity could enhance its salt resistance, especially at low cationicity, and the apparent viscosity was in direct proportion to the intrinsic viscosity of the P(DMC-AM) in salt solutions. Furthermore, salt effects (ionic radius, cationic valence, and anion valence) on the apparent viscosity were characterized. They clearly showed that the apparent viscosity was decreased with the increase of ion radius and ion valence. In particular, a difference in polymer aggregation was found when multivalent cations or anions containing solvents were added; two schematic models describing the rheological behavior of the P(DMC-AM) molecules in multivalent salt solutions are proposed.

Preparation and evaluation of polymer-encapsulated UV filter nanocapsules with miniemulsion polymerization

Ultraviolet (UV) filter nanocapsules were prepared by encapsulating organic UV filter octyl dimethyl para-aminobenzoic acid (OD-PABA) with miniemulsion polymerization using an amphiphilic random copolymer poly(styrene-co-methacrylic acid) (P(St-co-MAA)) as an emulsifier, methyl methacrylate (MMA) as the monomer and ethylene glycol dimethacrylate (EGDMA) as the crosslinker. TEM showed that the nanocapsules had irregularly spherical shape with an average diameter of 320 nm, and OD-PABA crystalline grains were encapsulated. The molar ratio of St to MAA in P(St-co-MAA) and the polymer emulsifier concentration, as well as the molar ratio of MMA to EGDMA in polymer coating significantly influenced the encapsulation efficiency and the leakage rate. At the optimum conditions, the encapsulation efficiency of OD-PABA reached to 33%. OD-PABA leakage in isopropyl myristate (IPM) could be ignored since the leakage rate maintained 1.3% during continuous stirring for 24 h. UV reflectance spectra showed that the UV filter nanocapsules had broad-spectrum UV blocking owing to the absorbance of OD-PABA combined with the scattering and reflection of the nanocapsules at submicron level. The sun protection factor (SPF) of the UV filter nanocapsules sunscreen improved by 300% compared with the free OD-PABA formulations. Moreover, OD-PABA encapsulated in the nanocapsules could reduce the cytotoxicity significantly through the evaluation of the sunscreen safety with MTT method.

Well-defined high molecular weight polyglycolide-b-poly(L-)lactide-b-polyglycolide triblock copolymers: synthesis, characterization and microstructural analysis

Block copolymerization is already a proven technique to manipulate the properties of polymeric materials. Herein, our work presents a facile synthesis of high molecular weight polyglycolide-b-poly(L-)lactide-b-polyglycolide (b-PLLGA) triblock copolymers by ring-opening polymerization (ROP) in bulk at considerably low temperature. A series of ABA-type triblock copolymers was successfully prepared and microstructural properties were thoroughly investigated against random copolymers of poly(L-lactide-co-glycolide) (r-PLLGA). This synthesis method led to the preparation of high molecular weight b-PLLGAs with highly defined chain microstructure and an intrinsic viscosity [η] was obtained as high as 1.62 dl/g when [M]:[I] was [1]:[1000]. The investigations revealed that the prepared copolymers are in block type chain microstructure, having exclusive thermal transitions and sequence/segment properties. DSC analysis revealed that two glass (Tg) transitions and two melt transitions (Tm) exclusively associated to PGA block and PLLA block. Results were further confirmed by homosequenses of –LLLL- and -GGGG- from 13C-NMR spectroscopy. Tensile results revealed that b-PLLGA have higher tensile strength and Young’s modulus as compared to r-PLLGA. Moreover, b-PLLGAs are more thermally stable and have a wider thermal processing window.

Evaluation of Different Compatibilization Strategies to Improve the Performance of Injection-Molded Green Composite Pieces Made of Polylactide Reinforced with Short Flaxseed Fibers.

Green composites made of polylactide (PLA) and short flaxseed fibers (FFs) at 20 wt % were successfully compounded by twin-screw extrusion (TSE) and subsequently shaped into pieces by injection molding. The linen waste derived FFs were subjected to an alkalization pretreatment to remove impurities, improve the fiber surface quality, and make the fibers more hydrophobic. The alkali-pretreated FFs successfully reinforced PLA, leading to green composite pieces with higher mechanical strength. However, the pieces also showed lower ductility and toughness and the lignocellulosic fibers easily detached during fracture due to the absence or low interfacial adhesion with the biopolyester matrix. Therefore, four different compatibilization strategies were carried out to enhance the fiber–matrix interfacial adhesion. These routes consisted on the silanization of the alkalized FFs with a glycidyl silane, namely (3-glycidyloxypropyl) trimethoxysilane (GPTMS), and the reactive extrusion (REX) with three compatibilizers, namely a multi-functional epoxy-based styrene-acrylic oligomer (ESAO), a random copolymer of poly(styrene-co-glycidyl methacrylate) (PS-co-GMA), and maleinized linseed oil (MLO). The results showed that all the here-tested compatibilizers improved mechanical strength, ductility, and toughness as well as the thermal stability and thermomechanical properties of the green composite pieces. The highest interfacial adhesion was observed in the green composite pieces containing the silanized fibers. Interestingly, PS-co-GMA and, more intensely, ESAO yielded the pieces with the highest mechanical performance due to the higher reactivity of these additives with both composite components and their chain-extension action, whereas MLO led to the most ductile pieces due to its secondary role as plasticizer for PLA.

Synthesis and multicolor emission properties of polystyrene with difluoroboron avobenzone complexes at side chains

Random copolymers (poly(ABSt-co-St)) consisting of avobenzone-BF2 complex monomer (ABSt) and styrene (St) were synthesized and used for emission color tuning including white-like emission in the solid state using St units as a spacer. The emission color of ABSt in the resulting copolymers changed from green to blue via bluish-white by changing the content of St. The fluorescence quantum yields of the polymers in the solid state were relatively high (Φf = 0.30–0.51) independent of the composition contents. The polymers have two main emission bands around 440 and 540 nm, which were derived from the emission of single-molecule and amorphous aggregation, respectively. The fluorescence color changed according to a change in the ratio of the fluorescence intensity at 440 and 540 nm (F440/F540). The absorption and fluorescence properties of the polymers in tetrahydrofuran were independent of the composition ratio of ABSt and St, which indicates no intermolecular interaction between avobenzone-BF2 (AB) fluorophores in the intra-polymer chain. The emission color of all polymers in the solution was blue and the fluorescence spectra were the same as that of ABSt in the solution. Thus, emission color changes observed in the solid state were mainly derived from the intermolecular interaction between AB fluorophores in inter-polymer chains because the polymers intertwined each other in the solid state. When the polymers in the solid state were annealed, F440/F540 increased and all of the fluorescence spectra became similar to that of monomer emission according to the arrangement change of the polymer chain. It is concluded that emission color changes of the polymers are mainly derived from intermolecular interaction between AB fluorophores in the inter-polymer chains. We have demonstrated that poly(ABSt-co-St) forms excellent homogeneous fluorescence polymer films. In contrast, the mixture of methoxy AB (ABOMe) and poly(St) undergoes crystallization even in the low content of ABOMe in poly(St).

Thermo-responsive nanocarrier based on poly(N-isopropylacrylamide) serving as a smart doxorubicin delivery system

Smart temperature- and pH-responsive nanocarriers could be considered as potent vehicle in drug delivery systems. By this means, a thermo-responsive polymeric nanocarrier based on a random copolymer of poly(N-isopropylacrylamide-co-acrylamide) was prepared using controlled polymerization technique known as reversible addition fragmentation chain transfer (RAFT) polymerization. The presence of hydrophilic group in the chain, acrylamide, enhanced the lower critical solution temperature (LCST) to 37 °C in agreement with body normal temperature and made the structure suitable for drug delivery purposes. To reach this goal, the as-prepared structure was modified with hydrazine and then the anti-cancer drug, doxorubicin, was conjugated to hydrazine-modified chains through a Schiff-base linkage (acid-cleavable bond) to provide nanodrug carrier capable of responding to heat and pH. The product of each step was characterized with defined techniques. 1HNMR spectroscopy provided data for molecular weight determination. The hydrodynamic size was figured out by dynamic light scattering to be less than 300 nm. A comprehensive study on the topology of nanodrug carrier was performed by scanning electron microscopy, and the structural changes below and above the LCST were followed by transmission electron microscopy and atomic force microscopy which showed coil-like composition to globule assembly at temperature above the LCST. Furthermore, the release pattern of nanodrug carrier was assessed in the simulated medium of healthy organs or cancer tissue with pH 7.4 and 5 (37 and 42 °C). Finally, the cytotoxicity assay was performed on breast cancer/MCF-7 cell line which showed high potential of nanodrug carrier as a highly intelligent anti-cancer agent.

Tailoring Cationic Helical Polypeptides for Efficient Cytosolic Protein Delivery

Protein delivery is of central importance for both diagnostic and therapeutic applications. However, protein delivery faces challenges including poor endosomal escape and thus limited efficiency. Here, we report the facile construction and screening of a small library of cationic helical polypeptides for cytosolic protein delivery. The library is based on a random copolymer poly(γ-{2-[2-(2-methoxyethoxy)ethoxy]ethoxy}esteryl-L-glutamate)-randompoly(γ-6-chlorohexyl-L-glutamate)[P(EG3-r-ClC6)Glu], which is then modified with various pyridine derivatives and alkyl thiols. Flow Cytometry, confocal laser scanning microscopy, and viability assay collaboratively identify two leading polymers, showing efficient delivery of enhanced green fluorescent protein(eGFP) and low cytotoxicity. This finding is further validated by the cytosolic delivery of RNase A and cytochrome C(Cyt C) to HeLa cells in the viability assay. Together, this work demonstrates that high-throughput screening is an effective and viable approach to the selection of cationic helical polypeptides for the cytosolic delivery of functional proteins.

Microencapsulation of phase change material in water dispersible polymeric particles for thermoregulating rubber composites—A holistic approach

Summary To avoid the leakage of phase change materials (PCM) to its surrounding, microencapsulation of PCM in a polymeric shell is highly desirable. These microcapsules ideally should provide a platform to store and release latent heat of the PCM without undergoing any physicochemical transformation of core (PCM) as well as shell (polymer) materials. Several characteristics such as heat transfer efficiency, thermal conductivity, water dispersibility, and durability of the PCM capsules are dependent on the nature of shell materials. In the present study, a random copolymer of poly (methyl methcrylate-co-2-hydroxyethyl methacrylate) poly (MMA-co-HEMA) with an optimum ratio of 75/25 (methyl methacrylate (MMA)/2-hydroxyethyl methacrylate (HEMA)) was used as shell material to encapsulate paraffin wax (PCM), using emulsion solvent evaporation method. The microcapsules of ~5-μm size with a shell thickness of ~0.8 μm with high encapsulation efficiency (~92.34%) and thermal storage capability (99.85%) were fabricated. In addition to ease of water dispersibility, PHEMA (poly(2-hydroxyethyl methacrylate)) containing water absorbable shells also exhibit enhanced thermal conductivity from 0.1 to 0.49 W/(m·K) at 25°C in wet state compared with the dry capsule. The capsules show good durability by displaying no significant change in thermal properties and water dispersibility after running through 500 heating/cooling cycles. To test the feasibility of this novel water dispersible microencapsulated PCM, these were mixed with natural rubber latex at various blend ratios, and their thermal behaviour was evaluated. The obtained rubber composite showed good thermoregulation property with enhanced mechanical strength.

Tailoring the surface of attapulgite by combining redox-initiated RAFT polymerization with alkynyl-thiol click reaction for polycarbonate nanocomposites:Effect of polymer brush chain length on mechanical, thermal and rheological properties

In this work, we proposed the tuning of the interface between attapulgite (ATP) and polycarbonate (PC) by the surface tailoring of ATP via a combination of RAFT polymerization and alkynyl-thiol click reaction. The side alkynyl-functionalized random copolymer poly(MMA-co-PgMA) was synthesized as the immobilization block via redox-initiated room-temperature RAFT copolymerization of MMA and propargyl methacrylate (PgMA). Then, the dispersion block was synthesized by room-temperature RAFT polymerization of MMA using poly(MMA-co-PgMA) as the macro chain transfer agent to afford poly((MMA-co-PgMA)-b-MMA). FTIR, 1H NMR, gel permeation chromatograph (GPC), and kinetic results indicated the successful synthesis of copolymers with well-defined structures. Copolymers with different length of PMMA segment were tethered onto the surface of thiol-functionalized ATP via alkynyl-thiol click reaction to mediate the interfacial interaction between ATP and PC, the successful covalent grafting of copolymers was confirmed by FTIR, TGA, XPS and XRD, and the effects of dispersion blockchain length on nanocomposites were investigated. The functionalized ATP demonstrated an improved dispersity in nanocomposites and enhanced mechanical properties with increasing dispersion blockchain length. The PC nanocomposites with functionalized ATP showed lower Tg and complex viscosity as compared to that of pure PC and nanocomposites with bare ATP, which enhanced the processability of nanocomposites.

Crystallization Retardation of Ultrathin Films of Poly[(R)-3-hydroxybutyrate] and a Random Copolymer Poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyhexanoate] on an Aluminum Oxide Surface

Ultrathin films of biodegradable poly[(R)-3-hydroxybutyrate] (PHB) and its random copolymer poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyhexanoate] (PHBHx) were prepared by spin-coating onto aluminum substrates with a naturally oxidized aluminum oxide (AO) surface layer or, alternatively, on gold substrates. The opposite surface of the film was in contact with ambient air. Isothermal crystallization kinetics of these films at room temperature were studied using infrared reflection absorption spectroscopy. The overall crystallization rate for all the polymers when crystallizing on AO is significantly retarded compared with the same polymer crystallizing on gold. It was found that the retardation effect was not due to a confinement effect. The crystallization retardation effect was especially enhanced for PHBHx with a higher (R)-3-hydroxyhexanoate content. Avrami analysis showed that the crystallization rate constant k (min–1) for all of the polymers on AO is approximately 3 to 4 orders of magnitude less than...

Synthesis and Properties of Reversible Disulfide Bond-based Self-healing Polyurethane with Triple Shape Memory Properties

A reversible disulfide bond-based self-healing polyurethane with triple shape memory properties was prepared by chain extending of random copolymer poly(lactide-co-caprolactone) (PCLA), hexamethylene diisocyanate (HDI), polytetrahydrofuran (PTMEG), and 4,4′-aminophenyl disulfide. The chemical structures were characterized using 1H nuclear magnetic resonance (1H-NMR) spectroscopy, Fourier transform infrared spectroscopy (FTIR), and gel permeation chromatography (GPC). The thermal properties, self-healing properties, triple-shape memory effect, and quantitative shape memory response were evaluated by differential scanning calorimetry (DSC), tensile tests, two-step programming process thermal mechanical experiments, and subsequent progressive thermal recovery. The self-healing mechanism and procedures were investigated using polarizing optical microscopy (POM) and an optical profiler. It was concluded that self-healing properties (up to 60%) and triple-shape memory properties around 35 and 50 °C (with shape fixation ratios of 94.3% and 98.3%, shape recovery ratios of 76.6% and 85.1%, respectively) were integrated to the shape memory polyurethane. As-prepared polyurethane is expected to have potential applications in multi-shape coatings, films, and step-by-step deploying structures.