Mechanism Of Poly Research Articles

Investigating on the Performance and Mechanism of Poly(styrene-methyl methacrylate-ethyl methacrylate-butyl acrylate) as Nano Sealing Agent in Oil-Based Drilling Fluids.

Conventional micron sealants are unable to effectively seal nanopores and fractures in shale formations, and the development of new nanomaterials has now become a major research focus to address the instability of shale gas wells. In this paper, oil-based drilling fluids (ODFs) sealants named SMEB (poly(styrene-methyl methacrylate-ethyl methacrylate-butyl acrylate)) were synthesized by free radical polymerization. The SMEB has been characterized by Fourier transform infrared spectroscopy (FTIR), laser scattering analysis (LSA), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The effect of SMEB on the rheological properties of drilling fluids was evaluated by assessing the changes in the rheological parameters of ODFs before and after aging. In addition, the sealing performance of SMEB in ODFs was investigated by high-temperature, high-pressure (HTHP) fluid loss tests and HTHP dense core permeability tests. The results indicated that the particle size of SMEB ranged from 60.68 to 157.39 nm, with a median size of 89.62 nm. The initial decomposition temperature of SMEB was 334 °C, which was in line with the requirement of high-temperature resistance for materials used in shale gas wells. The addition of SMEB has minimal effect on the rheological properties of the drilling fluids and did not adversely affect its performance. At 150 °C and 3.5 MPa, the sealing efficiency of the simulated mud cake was 59.69% with a measured permeability of 0.77 × 10-4 mD at a concentration of 0.5 wt % SMEB. Additionally, when 0.5 wt % SMEB was applied to artificial cores at 105 °C and 3.5 MPa, the sealing efficiency was as high as 86.70%, and the corresponding permeability was 0.48 × 10-3 mD. SMEB demonstrated excellent sealing capabilities in both simulated mud cake and artificial cores, reducing and preventing drilling fluids filtrate flow into the formation. Therefore, SMEB can be applied to drilling fluids as a novel sealing agent and make a significant contribution to maintaining wellbore stability.

Changes in properties and mechanism of poly(p-phenylene terephthalamide) activated carbon paper prepared by different activation methods

Changes in properties and mechanism of poly(p-phenylene terephthalamide) activated carbon paper prepared by different activation methods

Thermal decomposition kinetics and mechanism of poly(ethylene 2,5-furan dicarboxylate) Nanocomposites for food packaging applications

Poly(ethylene 2,5-furan dicarboxylate) (PEF) based nanocomposites containing different nanoparticles like Ag, TiO2, ZnO, ZrO2 Ce-Bioglass, have been synthesized via in-situ polymerization techniques targeting food packaging applications. Zeta potential measurements showed an increase in the negative zeta potential value due to an increase in the surface charge density of the nanocomposites. Thermogravimetric analysis results proved that, except PEF-ZnO nanocomposite, all the other nanocomposites exhibited good resistance to thermal degradation without serious mass loss until 330 °C. Thermal decomposition kinetic analysis and the dependence of activation energy on the degree of conversion (α), indicated that the presence of ZnO nanoparticles influences, the degradation mechanism of PEF. In contrast, the presence of Ce-Bioglass nanoparticles leads to a slower degradation process, contributing to the enhanced resistance to thermal degradation of the PEF-Bioglass nanocomposite. The thermal degradation mechanism of PEF nanocomposites analyzed by pyrolysis‒gas chromatography/mass spectrometry (Py-GC/MS) indicated that the primary thermal degradation mechanism for the studied nanocomposites was β-hydrogen bond scission, while to a lesser extent, α-hydrogen bond scission products were noted in PEF-TiO2 and PEF-ZrO2 nanocomposites.

Host–Guest Interactions and Transport Mechanism in Poly(vinylidene fluoride)-Based Quasi-Solid Electrolytes for Lithium Metal Batteries

Host–Guest Interactions and Transport Mechanism in Poly(vinylidene fluoride)-Based Quasi-Solid Electrolytes for Lithium Metal Batteries

Electrochemical Synthesis and Characterization of Poly(p-Toluidine-co-o-aminophenol) Copolymers: Influence of Monomer Ratio

Conducting polymers, particularly poly(p-toluidine) (PPT) and its copolymer films with poly(o-aminophenol) [poly(PT-co-OAP)], have gained significant attention due to their diverse applications in batteries, electronic devices, sensors, etc. The copolymers were prepared using electrochemical method using cyclic voltammetry on an indium tin oxide (ITO) coated glass plate immersed in a solution of 1 M HCl. The influence of the monomer ratio on the resulting copolymerization and electrochemical behaviour was also investigated. Additionally, a possible mechanism for Poly(PT-co-OAP) formation in an acidic medium is also deduced. The synthesized copolymers were thoroughly characterized using IR, UV-Vis, PXRD, SEM and conductivity analysis.

Molecular dynamics study on the mechanism of poly(amic acid) chemical structure on thermal imidization process and polyimide architecture

In this work, the thermal imidization of 3,3′, 4,4′-biphenyltetracarboxylic dianhydride/p-phenylenediamine (BPDA/PDA), pyromellitic dianhydride/4,4′-oxydianiline (PMDA/ODA), 4,4′-oxydiphthalic anhydride/4,4′-oxydianiline (ODPA/ODA), and 4,4'-(hexafluoroisopropylidene)diphthalic anhydride/2,2′-bis(trifluoromethyl)benzidine (6FDA/TFMB) polyimides (PIs) were investigated based on molecular dynamics (MD) simulation. It was found that two kinds of imide bonds were formed, i.e., inter-molecular and intra-molecular imide bonds, which results in differences in the final architecture of the target PI systems. The BPDA/PDA and PMDA/ODA PIs present crosslinking network structure, while the ODPA/ODA PI shows a hybrid structure composed of crosslinking and linear fragments, and the 6FDA/ODA PI displays linear and branched structures. Compared with the previous view of linear PI molecular chains, these results agree well and better account for the thermoset of PMDA/ODA and BPDA/PDA, thermoplasticity of ODPA/ODA, and solubility of 6FDA/TFMB. The mechanism causing the above differences was studied from radial distribution function (RDF), coordination number, fractional free volume (FFV), and density field analysis. By comparing the experimental and simulated values of glass transition temperature and modulus of PI models, the rationality of inter-molecular imide bonds is proved. In addition, through the PAA/DMF compound models, it was found that the increase of solvent content hindered the formation of inter-molecular imide bonds. This study provides new insights into the thermal imidization process and the final architecture of PIs derived from poly(amic acid).

Influence of Clay on Structure, Thermal Properties and Mechanics of Poly(vinyl acetate)/Maghnite Nanocomposites.

AbstractPoly (vinyl acetate) (PVAC) based on Algerian clay maghnite was synthesized by an emulsion polymerization process in the present study. The prepared nanocomposites were analyzed by means of FTIR, UV‐visible, XRD, AFM, SEM, TGA and optical microscopy. The results obtained showed a semi‐crystalline structure of the composite system revealed by the XRD scheme. The addition of maghnite to the fillers up to 5 wt % has been shown to reduce the optical band gap energy, while the refractive index is greatly increased. The presence of maghnite in PVAC leads to an increase in surface roughness as measured by AFM analysis. The thermal stability of PVAC was significantly improved by the presence of maghnite in the polymer matrix. The mechanical test results indicate that the tensile strength of the polymer composites was improved by the increase in the concentration of clay platelets. The electrical property data show that as the frequency increases, the dielectric constant decreases and the electrical conductivity increases. The loading content of composites also influences their electrical and mechanical properties. This widens the range of applications for these materials in flexible electronics and in conductive coatings.

SiO2 nanofiber reinforced P(VdF-HFP) based microporous polymer electrolytes for advanced energy storage applications

The application of ceramic nanofiller-dispersed microporous polymer gel electrolytes (MPGEs) in energy storage devices has been a subject of utmost research importance for a long time. However, a clear understanding of ion transport properties in this type of electrolyte is not yet achieved. The present article includes a detailed investigation of the uptake kinetics and ion transport mechanism in poly(vinylidene fluoride-co-hexafluoropropylene) [P(VdF-HFP)] based MPGEs reinforced with silica (SiO2) nanofibers. Very high ionic conductivity of 9.21 × 10−3 Scm−1 at ambient temperature has been achieved at a relatively low uptake ratio of 212 %, maintaining the dimensional integrity of the films when nanofiber content in P(VdF-HFP) is 2.5 wt%. This result ascertains the role of nanofibers in promoting ion transport in MPGEs, as revealed by XRD, FTIR, XPS, and simulative computational studies. The diffusive behavior of the MPGEs has been analyzed for both the liquid and the gel phases of the porous polymer membranes. The maximum diffusion coefficients for gel and liquid phases are 2.83 × 10−6 cm2s−1 and 2.36 × 10−12 cm2s−1, respectively, when the weight ratio of nanofiber is 2.5 %, confirming that the gel phase is the dominant conducting phase in MPGEs. The nanofiber-reinforced MPGEs show the highest electrochemical potential window of 4.6 V and excellent interfacial stability at 2.5 wt% of nanofiber concentrations. Nanofiber loaded MPGE also exhibits extreme non-flammability, which can be exposed to the flame for longer without burning. Being highly conductive with outstanding electrochemical, interfacial and flame retardant properties, the synthesized MPGEs could be a suitable candidate for next-generation energy-storing devices.

Poly (ADP-ribose) polymerases 16 triggers pathological cardiac hypertrophy via activating IRE1α–sXBP1–GATA4 pathway

BackgroundPressure overload-induced pathological cardiac hypertrophy is an independent predecessor of heart failure (HF), which remains the leading cause of worldwide mortality. However, current evidence on the molecular determinants of pathological cardiac hypertrophy is still inadequacy. This study aims to elucidate the role and mechanisms of Poly (ADP-ribose) polymerases 16 (PARP16) in the pathogenesis of pathological cardiac hypertrophy.MethodsGain and loss of function approaches were used to demonstrate the effects of genetic overexpression or deletion of PARP16 on cardiomyocyte hypertrophic growth in vitro. Ablation of PARP16 by transducing the myocardium with serotype 9 adeno-associated virus (AAV9)-encoding PARP16 shRNA were then subjected to transverse aortic construction (TAC) to investigate the effect of PARP16 on pathological cardiac hypertrophy in vivo. Co-immunoprecipitation (IP) and western blot assay were used to detect the mechanisms of PARP16 in regulating cardiac hypertrophic development.ResultsPARP16 deficiency rescued cardiac dysfunction and ameliorated TAC-induced cardiac hypertrophy and fibrosis in vivo, as well as phenylephrine (PE)-induced cardiomyocyte hypertrophic responses in vitro. Whereas overexpression of PARP16 exacerbated hypertrophic responses including the augmented cardiomyocyte surface area and upregulation of the fetal gene expressions. Mechanistically, PARP16 interacted with IRE1α and ADP-ribosylated IRE1α and then mediated the hypertrophic responses through activating the IRE1α–sXBP1–GATA4 pathway.ConclusionsCollectively, our results implicated that PARP16 is a contributor to pathological cardiac hypertrophy at least in part via activating the IRE1α–sXBP1–GATA4 pathway, and may be regarded as a new potential target for exploring effective therapeutic interventions of pathological cardiac hypertrophy and heart failure.

Poly(acrylic acid)-Assisted Intrafibrillar Mineralization of Type I Collagen: A Review.

The mineralization of type I collagen is a biological process occurring in vertebrates by which some hard tissues such as bone and dentin are constructed. Due to the extensive clinical needs for bone defect repair and remineralization of mineral-depleted dentin, biomimetic mineralization of collagen is attracting more and more interests. Synthetic analogs of noncollagenous proteins are necessary for directing the in vitro mineralization. In this paper, the function and mechanism of poly(acrylic acid) (PAA) in regulating the mineralization, especially intrafibrillar mineralization (IM) of collagen are reviewed. As two mineralization patterns (extrafibrillar and intrafibrillar) co-exist in natural hard tissues, differences between them in terms of microstructure, biodegradation, cytocompatibility, osteoinduction in vitro, and performance in vivo are systematically compared. Then the roles of PAA in biomimetic collagen IM within one-analog and two-analog systems are discussed, respectively. Moreover, mineralization of some self-mineralizable collagen matrices is described. Due to the interactions between collagen and PAA play a crucial role in the processes of collagen mineralization, some reference researches are also provided involving the collagen/PAA interactions in some other fields. Finally, this review is ended with an outlook for future potential improvements based on the collection of existing bottlenecks in this field.

Investigation of Poly(MM-EM-BM) as Nanosealing Materials in Oil-Based Drilling Fluids: Synthesis and Evaluation.

Nanosealing technology has become the key to overcoming the wellbore instability problem in deep and ultradeep shale formations. In this Article, the terpolymer poly(MM-EM-BM) was synthesized from methyl methacrylate, ethyl methacrylate, and butyl methacrylate by a Michael addition reaction. The poly(MM-EM-BM) nanoparticles were investigated by Fourier transform infrared spectroscopy, laser scattering analysis, and thermogravimetric analysis. The results imply that the particle size range of poly(MM-EM-BM) is between 33.90 and 135.62 nm and the average diameter is about 85.95 nm at room temperature, which can maintain excellent stability at 382.75 °C. The effects of poly(MM-EM-BM) on the properties of oil-based drilling fluids (OBDFs) were ascertained through experiments on the rheological performance, electrical stability, and high-temperature and high-pressure (HTHP) filtration loss. The results suggested that when the amount of added poly(MM-EM-BM) increases, the apparent viscosity, plastic viscosity, dynamic shear force, and demulsification voltage of the drilling fluids will increase correspondingly; in contrast, the HTHP filtration loss gradually decreased. When poly(MM-EM-BM) is added at 0.75%, the kinetic-to-plastic ratio of the drilling fluids is 0.24 and the filtration loss is 0.6 mL, showing excellent overall performance. The drilling fluids have a good rock-carrying ability and water loss wall-building property. The sealing performance and mechanism of poly(MM-EM-BM) were researched by the method of a sealing performance test under high temperature. The results indicated that the more poly(MM-EM-BM) used, the higher the sealing efficiency of the mud cake and the core as the sealing medium. When poly(MM-EM-BM) was added at 0.75%, the sealing rates of the mud cake and the core as the sealing medium reached the maximum sealing rates of 40.30% and 91.48%, respectively. When poly(MM-EM-BM) enters the core nanopore joint for a certain distance under formation pressure, a tight sealing layer will be formed to effectively prevent the entry of filtrate. Poly(MM-EM-BM) as a potential oil-based nanosealing agent is expected to solve the problem caused by wellbore instability in shale horizontal wells.

Poly I:C Exacerbates Airway Inflammation and Remodeling in Cigarette Smoke-Exposed Mice

BackgroundChronic obstructive pulmonary disease (COPD) is a chronic respiratory disorder characterized by chronic inflammation and airway remodeling. Cigarette smoke (CS) and respiratory viruses are major causes of COPD development and exacerbation, but the mechanisms of these compounding factors on inflammation and pathological changes in airway structure still need further investigation.PurposeThis work aimed to investigate the effects and mechanisms of Poly I:C on pathological changes in CS-induced COPD mice, such as airway inflammation and remodeling.MethodsFrom 1 to 8 weeks, the mice were exposed to CS, Poly I:C, or a combination of both. To compare the pathological changes among different groups over time, the mice were sacrificed at week 4, 8, 16, and 24, then the lungs were harvested to measure pulmonary pathology, inflammatory cytokines, and airway remodeling.ResultsOur data revealed that the fundamental characteristics of COPD, such as pulmonary pathological damage, the release of inflammatory mediators, and the remodeling of airway walls, were observed at week 8 in CS-exposed mice and these pathological changes persisted to week 16. Compared with the CS group, the pathological changes, including decreased lung function, inflammatory cell infiltration, alveolar destruction, and airway wall thickening, were weaker in the Poly I:C group. These pathological changes were observed at week 8 and persisted to week 16 in Poly I:C-induced mice. Furthermore, Poly I:C exacerbated lung tissue damage in CS-induced COPD mice. The decreased lung function, airway inflammation and remodeling were observed in the combined group at week 4, and these pathological changes persisted to week 24. Our research indicated that Poly I:C enhanced the expression of p-P38, p-JNK and p-NF-κB in CS-exposed mice.ConclusionPoly I:C could promote airway inflammation and remodeling in CS-induced COPD mice probably by NF-κB and MAPK signaling.

Mechanisms Related to Inhibition of Fungal Biofilm Formation on Medical Device Coated with Poly(Methylmethacrylate-co-Dimethylacrylamide)

Candida albicans (C. albicans) are the most common cause of urinary fungal infections. C. albicans biofilms are of increasing clinical importance due to their resistance to antifungal therapy. Since the use of medical devices causes most hospital infections, polymeric coatings that reduce microorganisms adhesion and biofilm formation are considered an attractive strategy. In this work, the ability and possible mechanisms of poly(methylmethacrylate-co-dimethylacrylamide) (PMMDMA) to inhibit C. albicans biofilms on medical devices have been studied. Scanning electron microscopy was used to evaluate fungal adhesion at various pH conditions, while the surface roughness of the coated and uncoated catheters was analyzed by atomic force microscopy. The surface charge was assessed, and the contact angle was determined to evaluate the surface hydrophobicity. PMMDMA coated catheters showed reduced binding of C. albicans at all pH values studied and presented a hydrophilic contact angle of ϴ = 71°. Negative zeta potential values of PMMDMA enhanced the reduction in C. albicans binding. AFM images demonstrated a smoother and homogeneous surface of PMMDMA-coated catheters. Coating with PMMDMA provided a smoother, more hydrophilic, and negative-charged surface, contributing to a substantial reduction of C. albicans binding.

Structural aspect on “Salting-in” mechanism of PEG chains into a phosphonium-based ionic liquid using lithium salt

A study on the “salting-in” mechanism of poly(ethylene glycol) (PEG) into triethylpentylphosphonium bis(trifluoromethanesulfonyl)amide ([P2225][TFSA]) ionic liquid with LiTFSA salt is presented. There was no dissolution of PEG chains into [P2225][TFSA] in the absence of LiTFSA salt. However, salting-in dissolution occurred when LiTFSA salt was added irrespective of the molecular weight of PEG. Raman spectral analysis revealed that the TFSA anions trapped within the Li-ion coordination complex (i.e., [Li(TFSA)2]–) in [P2225][TFSA] solution are easily decoordinated when PEG-chains are added to form stable Li+⋯PEG complexes; in other words, Li ions preferentially interact with O atoms of PEG over those of TFSA anion. High-energy X-ray total scattering (HEXTS) and all-atom molecular dynamics (MD) simulations were combined to elucidate the detailed structures of the salting-in dissolved PEG chains at the molecular level. Some of the notable characteristics are as follows: (1) In PEG/[P2225][TFSA] solution (without LiTFSA salt), the PEG chains struggle to interact with the P2225 cations because of weaker PEG–P2225+ interactions, resulting in the incompatibility of PEG/[P2225][TFSA] with shrink polymer chains. (2) When LiTFSA is added to the solution, the Li ions bound to the PEG chains act as a solvation site for solvent IL (in this case, TFSA anions). (3) Interactions between PEG-coordinated Li+ and TFSA– trigger the polymer chains to expand, resulting in “salting-in” dissolution of PEG.

Study on Hydrolysis Properties and Mechanism of Poly(3-Methacrylamido Propyl Trimethyl Ammonium Chloride) Solution.

Poly(3-methacrylamido propyl trimethyl ammonium chloride) (PMAPTAC) is a typical cationic water-soluble polyelectrolyte, which has been widely used in petroleum, papermaking, daily cosmetics and other fields in the form of an aqueous solution. However, the acid–base and thermal stability of PMAPTAC in aqueous solution have not been reported yet, which hinders its further application in high-temperature and acid–base environments. To address these deficiencies, the effects of temperature and pH of PMAPTAC with different intrinsic viscosities on its hydrolysis stability were investigated qualitatively and quantitatively, and the hydrolysis mechanism was studied. Firstly, the qualitative analysis showed that the apparent viscosity of the PMAPTAC solution decreased with hydrolysis time at different temperatures and pH. The higher the temperature and the lower the pH, the greater the viscosity loss of PMAPTAC. The quantitative analysis showed that the hydrolysis rate of the PMAPTAC sample solution increased with the increase in temperature and pH. In addition, the intrinsic viscosity of PMAPTAC samples had little effect on the hydrolytic stability of PMAPTAC. Secondly, by analyzing the viscosity curves at different pH and temperatures by Arrhenius analysis, the Arrhenius equations were found to be 1/τ = 200.34e^((−25.04)/RT), 1/τ = 9127.07e^((−38.90)/RT) and 1/τ = 4683.03e^((−39.89)/RT) for pH 3, pH 7 and pH 11, respectively. Thirdly, the hydrolysis rate of PDMC was the fastest under alkaline conditions. In addition, compared with PDMC, PMAPTAC had better hydrolysis stability under the same conditions. Finally, the mechanism of the hydrolyzed polymer was studied by FTIR and 13CNMR, which showed that the carbonyl group of PMAPTAC was hydrolyzed into a carboxyl group, and the small molecule (3-aminopropyl) trimethylammonium chloride was generated, while the ester group of PDMC was hydrolyzed into a carboxyl group, and choline chloride was released. The above results can provide a theoretical basis for the application of PMAPTAC in some high-temperature and acid–base environments.

Mechanism of poly(lactic acid-glycolic acid) (PLGA) copolymer nanoparticles in enhancing cytotoxicity against occurrence and development of lung cancer metastasis

Poly lactic acid-glycolic acid copolymer (PLGA) plays a critical role in inducing tumor cells apoptosis. However, the solubility of the compound itself puts a limit on its use value in treatment of tumor. In this study, we used PLGA combined with nanoparticles as a strategy for metastatic tumor of lung cancer. We evaluated the biological effect of PLGA nanoparticles on enhancing cytotoxicity and its anti-tumor effect against metastasis tumor of lung cancer. Confocal microscope was used to detect the transfection efficiency of tumor cells. PLGA and PLGA-cored nanoparticles (PLGA AC-NPs) were used to interfere with proliferation and apoptosis of metastatic tumor cell line from lung cancer and flow cytometry was used to explore its effect. Furthermore, PLGA and PLGA AC-NPs were injected into the chest of lung cancer mice for treatment. Cell proliferation and apoptosis were detected through measurement of tumor volume, immunohistochemistry (IHC) and Westernblot protein analysis. It was found that, PLGA AC-NPs significantly enhanced cell uptake while PLGA ACNPs regulated tumor by inhibiting cell proliferation and promoting apoptosis. It was also observed in vivo transplanted tumor model that the growth of metastatic tumor of lung cancer was inhibited significantly by NGO-PEG-PEI/Cer, while proliferation and accelerated apoptosis were also slowed down. PLGA AC-NPs can inhibit tumor growth by promoting apoptosis and inhibiting further proliferation of tumor cells.

Intravenous liposomal vaccine enhances CTL generation, but not until antigen presentation

Adjuvant loaded nanoparticles are a potent strategy for developing effective combined cancer immunotherapies. A polyinosinic-polycytidylic acid (poly I:C) is a ligand for toll-like receptor 3 and a promising cancer adjuvant. However, regarding intravenous administration, the potential for and the mechanism of poly I:C loaded nanoparticles as a cancer vaccine are largely unknown. We investigated the effects of using a combination of poly I:C and an antigen loaded liposome for cancer immunotherapy and a key process for achieving effective antitumor immunity of the liposome system under conditions of intravenous vaccination. A poly I:C and ovalbumin (OVA) loaded octaarginine (R8) modified liposome (PoIC/OVA-R8L) drastically inhibited the systemic cytokine production derived from the poly I:C intravenous injection. Treatment with PoIC/OVA-R8L improved the immune status in B16-OVA tumors to an inflamed immune status and induced a significant combined antitumor effect with the anti-programmed cell death 1 ligand (PD-L1). In a mechanistic analysis compared with a high dose of the free form of poly I:C, interestingly, local cytokine production, maturation of antigen presenting cells and antigen presentation were comparable. Conversely, significant differences were identified in the processes after OVA-specific CTL generation. Collectively, our findings have implications for the development of intravenous liposomal vaccines.

Small dop of comonomer, giant shift of cloud point: Thermo‐responsive behavior and mechanism of poly(methylacrylamide) copolymers with an upper critical solution temperature

AbstractPoly(methylacrylamide) (PMAM) is a thermo‐responsive polymer with an upper critical solution temperature (UCST). Its cloud point (Tcp) is around 60 °C, unsuitable for certain biomedical and industrial applications. This study brought up a copolymerization strategy to tune the Tcp of PMAM with hydrophilic comonomers. Surprisingly, with a small portion of hydrophilic monomer doped, the Tcp of the PMAM copolymer can be significantly shifted. For instances, with ≤7 mol% of acrylamide or 1 mol% of oligo(ethylene glycol) methacrylate, the Tcp can be shifted in a wide range from ~69 to ~0 °C. Microdifferential scanning calorimetry demonstrated that the enthalpic effect during the phase transition of the solutions is indistinctive, while fluorescence measurement with pyrene as a probe revealed that the hydrogen‐bonding within polymer chains is enhanced by the hydrophobic aggregation of methyl groups. Therefore, the doped hydrophilic monomer could remarkably alter the ordering of water‐molecules and the extent for the aggregation of methyl groups, leading to the pronounced shifting in the Tcp of the copolymers. This work would facilitate the application of PMAM as smart polymer materials and guide the inventions of functional materials based on UCST polymers.

Study of the Cu[I]/Cu[II] catalytic system in 2,6-dimethylphenol polymerization to poly(phenylene oxide)

• Oxidative polymerization of 2,6-dimethylphenol catalyzed by Cu[I] and Cu[II] systems, i.e. CuBr/dbeda, Cu 2 O/Br 2 /dbeda, CuBr 2 /dbeda and CuCO 3 /Br 2 /dbeda. • Starting with Cu[I] compounds, produces the most active catalytic systems. • Novel mechanism of poly(phenylene oxide) synthesis was presented. The study of Allan S. Hay catalytic systems containing copper[I] and copper[II] complexes, ie. CuBr/dbeda (where dbeda = N , N'-di-(t‑butyl)ethylenediamine), Cu 2 O/Br 2 /dbeda CuBr 2 /dbeda and CuCO 3 /Br 2 /dbeda in the polymerization of 2,6-dimethylphenol(2,6-DMP) to poly(phenylene oxide) (PPO) was presented. In the presence of bromine in the amount of 4.5 Br 2 /Cu, the copper[II] catalysts formed the greater number of polymerization centers. The values of the molar mass as well as its distribution depended on the 2,6-DMP/Cu molar ratio and the reaction time. Polymer with the higher molar mass was obtained at the molar ratio 2,6-DMP/Cu = 1000 and with the use of the copper[I] catalyst. By increasing the 2,6-DMP/Cu ratio to 1800, polymer with the lower molar mass was prepared. The reverse effect was observed for the copper[II] catalyst. The mechanism of 2,6-DMP polymerization to PPO was proposed in presence of the used catalysts. Also, the role of the bromine excess in the process was explained. In this mechanism the copper system Cu[I]⇄Cu[II] is responsible for the formation of oxygen and para -carbon radicals which are the starting molecules to launch the polymer synthesis. The "bromine" system reversibly provides the Br 2 molecule to brominate 2,6-DMP. The resulting 4‑bromo-2,6-dimethylphenol forms a carbon radical in the reaction with copper[I] complex.

Fluorescence Behavior and Mechanisms of Poly(ethylene glycol) and Their Applications in Fe3+ and Cr6+ Detections, Data Encryption, and Cell Imaging

In contrast to conventional fluorescent polymers featured by large conjugation structures, a new class of fluorescent polymers without any conjugations is gaining great interest in immerging applications beyond the possibility to achieve by the conjugated polymers. Poly(ethylene glycol) (PEG), widely used in biomedical fields for a long time owing to its nontoxicity and nonimmunogenicity, is found to be fluorescence emissive in the solid state and in aqueous solution, though deemed as not fluorescent in numerous reports. Through systematic study under different conditions, the emission is ascribed to the cluster formation of its chains; thereby the blue-shift of the emission with the excitation wavelength was interpreted through the Forster resonance energy transfer. The clusterization was ascertained through size measurements, Fourier transform infrared spectroscopy, NMR analyses, and the dependence on temperature, pH, and nonsolvent presence. Tested in the presence of competitive metal ions, selective emission quenching by Fe³⁺ and Cr⁶⁺ was observed. PEG was used as a sensor for the detection of Cr⁶⁺, Fe³⁺, and H₂O₂, outperforming most of the reported sensors alike. Its uses for data encryption and cell imaging were also presented. This work provides therefore a novel face of PEG with great potential in a variety of emerging applications, in particular, as sensors in the biomedical area.