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2019 Volume 37 Issue 2
2019, 37(2):
Abstract:
2019, 37(2): 101-114
doi: 10.1007/s10118-019-2171-x
Abstract:
Two-dimensional (2D) polymers are fascinating as they exhibit unique physical, chemical, mechanical, and electronic properties that are completely different from those of traditional linear or branched polymers. They are very promising for applications in catalysis, separation, optoelectronics, energy storage, and nanomedicine. Recently, ultrathin 2D conjugated polymers have emerged as advanced materials for converting solar energy into chemical energy. The inherent 2D planar structure with in-plane periodicity offers many features that are highly desirable for photon-involved catalytic energy conversion processes, including high absorption coefficients, large surface areas, abundant surface active sites, and efficient charge separation. Moreover, the possibility of finely tuning the optoelectronic and structural properties through precise molecular engineering has opened up new opportunities for design and synthesis of novel 2D polymer nanosheets with unprecedented applications. Herein, we highlight recent advances in developing ultrathin 2D conjugated polymer nanosheets for solar-to-chemical energy conversion. Specifically, we discuss emerging applications of ultrathin 2D conjugated polymer nanosheets for solar-driven water splitting and CO2 reduction. Meanwhile, future challenges and prospects for design and synthesis of ultrathin 2D conjugated polymer nanosheets for solar fuel generation are also included.
Two-dimensional (2D) polymers are fascinating as they exhibit unique physical, chemical, mechanical, and electronic properties that are completely different from those of traditional linear or branched polymers. They are very promising for applications in catalysis, separation, optoelectronics, energy storage, and nanomedicine. Recently, ultrathin 2D conjugated polymers have emerged as advanced materials for converting solar energy into chemical energy. The inherent 2D planar structure with in-plane periodicity offers many features that are highly desirable for photon-involved catalytic energy conversion processes, including high absorption coefficients, large surface areas, abundant surface active sites, and efficient charge separation. Moreover, the possibility of finely tuning the optoelectronic and structural properties through precise molecular engineering has opened up new opportunities for design and synthesis of novel 2D polymer nanosheets with unprecedented applications. Herein, we highlight recent advances in developing ultrathin 2D conjugated polymer nanosheets for solar-to-chemical energy conversion. Specifically, we discuss emerging applications of ultrathin 2D conjugated polymer nanosheets for solar-driven water splitting and CO2 reduction. Meanwhile, future challenges and prospects for design and synthesis of ultrathin 2D conjugated polymer nanosheets for solar fuel generation are also included.
2019, 37(2): 115-128
doi: 10.1007/s10118-019-2193-4
Abstract:
The past decade has witnessed the booming developments of the new methodologies for noninvasive tumor treatment, which are considered to overcome the current limitation of low treating efficacy, high risk of tumor recurrence, and severe side effects. Among a variety of novel therapeutic methods, photothermal therapy, employing nanometer-sized agents as the heat generators under near-infrared (NIR) light irradiation to ablate tumors, gives new insights into noninvasive tumor treatments with minimal side effects. Although many nanomaterials possess photothermal effects, inorganic nanoparticles and polymers are the most competitive alternatives considering the high photothermal performance and good biocompatibility. In this review, we summarized the tumor photothermal therapy using the nanocomposites composed of inorganic nanoparticles and polymers. Extinction coefficient and photothermal transduction efficiency are the two main factors to evaluate the photothermal performance of nanocomposites in vitro. Considering the improvement in the stability, biocompatibility, blood circulation half-life, and tumor uptake rate after polymer coating, these nanocomposites should be designed with inorganic core and polymer shell, thus improving the tumor treating efficacy in vivo. Such structure fulfills the requirements of high photothermal performance and good bio-security, making it possible to achieve complete ablation for shallow and small tumors under the safe limitation of NIR laser power density.
The past decade has witnessed the booming developments of the new methodologies for noninvasive tumor treatment, which are considered to overcome the current limitation of low treating efficacy, high risk of tumor recurrence, and severe side effects. Among a variety of novel therapeutic methods, photothermal therapy, employing nanometer-sized agents as the heat generators under near-infrared (NIR) light irradiation to ablate tumors, gives new insights into noninvasive tumor treatments with minimal side effects. Although many nanomaterials possess photothermal effects, inorganic nanoparticles and polymers are the most competitive alternatives considering the high photothermal performance and good biocompatibility. In this review, we summarized the tumor photothermal therapy using the nanocomposites composed of inorganic nanoparticles and polymers. Extinction coefficient and photothermal transduction efficiency are the two main factors to evaluate the photothermal performance of nanocomposites in vitro. Considering the improvement in the stability, biocompatibility, blood circulation half-life, and tumor uptake rate after polymer coating, these nanocomposites should be designed with inorganic core and polymer shell, thus improving the tumor treating efficacy in vivo. Such structure fulfills the requirements of high photothermal performance and good bio-security, making it possible to achieve complete ablation for shallow and small tumors under the safe limitation of NIR laser power density.
2019, 37(2): 129-135
doi: 10.1007/s10118-019-2172-9
Abstract:
We present here the development of cholesterol (Chol)-modified dendrimer system for targeted chemotherapy of folate (FA) receptor-expressing cancer cells. In our study, poly(amidoamine) (PAMAM) dendrimers of generation 5 (G5) were functionalized step-by-step with Chol, fluorescein isothiocyanate (FI), and FA via a poly(ethylene glycol) (PEG) spacer (PEG-FA), and then acetamide to shield their remaining surface amines. The synthesized G5.NHAc-Chol-FI-PEG-FA (for short, G5-CFPF) dendrimers were utilized to encapsulate 10-hydroxycamptothecin (HCP), a hydrophobic anticancer drug. We find that each G5-CFPF dendrimer can encapsulate 13.8 HCP molecules. The complexes show a slower release profiles of HCP in a pH-dependent manner than the control complexes formed using the same dendrimers without Chol under the same conditions. Thanks to the targeting role played by FA, the complexes display a specific inhibition efficacy to FA receptor-expressing cervical cancer cells. The designed Chol-modified dendrimers may be adopted as a promising carrier for application in targeted cancer therapy.
We present here the development of cholesterol (Chol)-modified dendrimer system for targeted chemotherapy of folate (FA) receptor-expressing cancer cells. In our study, poly(amidoamine) (PAMAM) dendrimers of generation 5 (G5) were functionalized step-by-step with Chol, fluorescein isothiocyanate (FI), and FA via a poly(ethylene glycol) (PEG) spacer (PEG-FA), and then acetamide to shield their remaining surface amines. The synthesized G5.NHAc-Chol-FI-PEG-FA (for short, G5-CFPF) dendrimers were utilized to encapsulate 10-hydroxycamptothecin (HCP), a hydrophobic anticancer drug. We find that each G5-CFPF dendrimer can encapsulate 13.8 HCP molecules. The complexes show a slower release profiles of HCP in a pH-dependent manner than the control complexes formed using the same dendrimers without Chol under the same conditions. Thanks to the targeting role played by FA, the complexes display a specific inhibition efficacy to FA receptor-expressing cervical cancer cells. The designed Chol-modified dendrimers may be adopted as a promising carrier for application in targeted cancer therapy.
2019, 37(2): 136-141
doi: 10.1007/s10118-019-2190-7
Abstract:
Two aromatic co-polyamides were synthesized combining two diacid monomers containing bulky pendant groups, 5-(9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboximido)isophthalic acid (DEAIA) and 5-tert-butylisophthalic acid (TERT), with 4,4′-(hexafluoroisopropylidene)dianiline (HFA) or 2,3,5,6-tetramethyl-1,4-phenylenediamine (Durene) by direct polycondensation. The structures of the obtained aromatic co-polyamides were confirmed by FTIR, Raman and 1H-NMR. The co-copolyamide films, DHTH and DDTD, exhibited rms-roughness values between 0.94 and 1.60 nm, respectively. Moreover, they presented good thermal stability up to 300 °C. Young’s moduli of the co-polyamide films were between 4.1 and 4.3 GPa. X-ray diffraction results showed that the co-polyamide films were amorphous due to the incorporation of both bulky pendant groups, tert-butyl and dibenzobarrelene. The combination of bulky pendant groups provided intrinsically transparent co-polyamide films with a transmittance higher than 88% in the range of 400−780 nm. Due to these outstanding film and optical properties, they are suggested to be flexible substrates in applications for solar cell and other portable electronic devices.
Two aromatic co-polyamides were synthesized combining two diacid monomers containing bulky pendant groups, 5-(9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboximido)isophthalic acid (DEAIA) and 5-tert-butylisophthalic acid (TERT), with 4,4′-(hexafluoroisopropylidene)dianiline (HFA) or 2,3,5,6-tetramethyl-1,4-phenylenediamine (Durene) by direct polycondensation. The structures of the obtained aromatic co-polyamides were confirmed by FTIR, Raman and 1H-NMR. The co-copolyamide films, DHTH and DDTD, exhibited rms-roughness values between 0.94 and 1.60 nm, respectively. Moreover, they presented good thermal stability up to 300 °C. Young’s moduli of the co-polyamide films were between 4.1 and 4.3 GPa. X-ray diffraction results showed that the co-polyamide films were amorphous due to the incorporation of both bulky pendant groups, tert-butyl and dibenzobarrelene. The combination of bulky pendant groups provided intrinsically transparent co-polyamide films with a transmittance higher than 88% in the range of 400−780 nm. Due to these outstanding film and optical properties, they are suggested to be flexible substrates in applications for solar cell and other portable electronic devices.
2019, 37(2): 142-148
doi: 10.1007/s10118-019-2186-3
Abstract:
The solubility of initiator determines its distribution and the roles played in emulsion polymerization as well as the final products, but this is still lack of systematic investigation. The present work focuses on this issue by comparing the kinetic behaviors and product properties of styrene emulsion polymerization initiated by 2,2-azoisobutyronitrile (AIBN) and potassium persulphate (KPS). Compared to KPS-initiated emulsion polymerization, the AIBN-initiated polymerization was found to be insensitive to the type of emulsifier, and have high polymerization rate as well as narrow molecular weight distribution and particle size distribution. This result indicates the effective free radicals are generated in micelles or colloids, which could decrease the proportion of homogeneous nucleation and make the process and product more controllable. As a consequence, there is a linear relationship between molecular weight of product and AIBN concentration in lg-lg coordinate. It provided a reference for the preparation of latexes with specified molecular weight and supported the possibility of the coexistence of multiple free radicals in one micelle or colloid when using oil-soluble initiator.
The solubility of initiator determines its distribution and the roles played in emulsion polymerization as well as the final products, but this is still lack of systematic investigation. The present work focuses on this issue by comparing the kinetic behaviors and product properties of styrene emulsion polymerization initiated by 2,2-azoisobutyronitrile (AIBN) and potassium persulphate (KPS). Compared to KPS-initiated emulsion polymerization, the AIBN-initiated polymerization was found to be insensitive to the type of emulsifier, and have high polymerization rate as well as narrow molecular weight distribution and particle size distribution. This result indicates the effective free radicals are generated in micelles or colloids, which could decrease the proportion of homogeneous nucleation and make the process and product more controllable. As a consequence, there is a linear relationship between molecular weight of product and AIBN concentration in lg-lg coordinate. It provided a reference for the preparation of latexes with specified molecular weight and supported the possibility of the coexistence of multiple free radicals in one micelle or colloid when using oil-soluble initiator.
2019, 37(2): 149-156
doi: 10.1007/s10118-019-2183-6
Abstract:
Four polymers containing five-membered rings in the main chain, with or without conjugation structure along the backbone and with or without conjugated pendent groups, were designed and synthesized by metathesis cyclopolymerization of functionalized α,ω-diynes, and cyclopolymerization of functionalized α,ω-dienes catalyzed by the α-diimine palladium-based catalyst, respectively. High to moderate monomer conversions were achieved. Chain structure, molecular weight, and molecular weight distribution (MWD) of the cyclopolymerization products were characterized by 1H-, 13C-NMR, FTIR, and GPC. The polymers showed regular main chain structures, moderately high molecular weight, and narrow MWD. Thermal properties and chain stacking behaviors of the polymers were investigated by differential scanning calorimetry (DSC) and X-ray diffraction (XRD) as well as atomic force microscopy (AFM). The polymer with conjugation system in both the backbone and the pendent groups exhibited UV-Vis absorption at a much longer wavelength than those with the conjugation only in the backbone or only in the side groups. The polymers with conjugated backbone need more space for chain stacking, and the conjugated backbone causes enhanced size of polymer particles assembled from solution. The results showed that primary microstructures of the polymer exerted significant influences on the physical properties.
Four polymers containing five-membered rings in the main chain, with or without conjugation structure along the backbone and with or without conjugated pendent groups, were designed and synthesized by metathesis cyclopolymerization of functionalized α,ω-diynes, and cyclopolymerization of functionalized α,ω-dienes catalyzed by the α-diimine palladium-based catalyst, respectively. High to moderate monomer conversions were achieved. Chain structure, molecular weight, and molecular weight distribution (MWD) of the cyclopolymerization products were characterized by 1H-, 13C-NMR, FTIR, and GPC. The polymers showed regular main chain structures, moderately high molecular weight, and narrow MWD. Thermal properties and chain stacking behaviors of the polymers were investigated by differential scanning calorimetry (DSC) and X-ray diffraction (XRD) as well as atomic force microscopy (AFM). The polymer with conjugation system in both the backbone and the pendent groups exhibited UV-Vis absorption at a much longer wavelength than those with the conjugation only in the backbone or only in the side groups. The polymers with conjugated backbone need more space for chain stacking, and the conjugated backbone causes enhanced size of polymer particles assembled from solution. The results showed that primary microstructures of the polymer exerted significant influences on the physical properties.
2019, 37(2): 157-163
doi: 10.1007/s10118-019-2176-5
Abstract:
Based on the preparative experiments of the light-emitting diode (LED) encapsulant, three types of monomer models with different functional groups are carried out to study the polymerization process by dynamic Monte Carlo (DMC) simulation and bond fluctuation model (BFM). We calculate the degree of polymerization, the radius of gyration and the frequency of void spheres to discuss the polymerization process, the molecular size and the spatial distribution at different volume fractions and proportions. Our results are in agreement with Grest’s decay rate and Flory’s scale law. Simulations show that the polymerization process depends on the appropriate volume fraction and proportion exceedingly, and the volume contraction in the polymerization process can also be observed in this study. These investigations could provide some insights into the understanding of the polymerization process of the encapsulant and help us to adjust the parameters in later experiments.
Based on the preparative experiments of the light-emitting diode (LED) encapsulant, three types of monomer models with different functional groups are carried out to study the polymerization process by dynamic Monte Carlo (DMC) simulation and bond fluctuation model (BFM). We calculate the degree of polymerization, the radius of gyration and the frequency of void spheres to discuss the polymerization process, the molecular size and the spatial distribution at different volume fractions and proportions. Our results are in agreement with Grest’s decay rate and Flory’s scale law. Simulations show that the polymerization process depends on the appropriate volume fraction and proportion exceedingly, and the volume contraction in the polymerization process can also be observed in this study. These investigations could provide some insights into the understanding of the polymerization process of the encapsulant and help us to adjust the parameters in later experiments.
2019, 37(2): 164-177
doi: 10.1007/s10118-019-2178-3
Abstract:
Blend based polymer nanocomposites, comprising Janus nanoparticles at their polymer/polymer interface, were analytically/experimentally evaluated. The modeling procedure was performed in two stages: first, modeling of polymer/polymer interface region comprising Janus nanoparticles and second, modeling of the entire systems as a function of the variation of the blend morphology. In the first stage, the modeling procedure was performed based on the development of the model proposed by Ji et al. and in the second stage, the fundamental of Kolarik’s model was used in order to propose a developed and more practical model. It was shown that Janus nanoparticles may form dual polymer/particle interphase at polymer/polymer interface which can drastically affect the final mechanical properties of the system. Comparing the results of tensile tests imposed on different prepared samples with the predictions of the model proved its accuracy and reliability (error < 9%).
Blend based polymer nanocomposites, comprising Janus nanoparticles at their polymer/polymer interface, were analytically/experimentally evaluated. The modeling procedure was performed in two stages: first, modeling of polymer/polymer interface region comprising Janus nanoparticles and second, modeling of the entire systems as a function of the variation of the blend morphology. In the first stage, the modeling procedure was performed based on the development of the model proposed by Ji et al. and in the second stage, the fundamental of Kolarik’s model was used in order to propose a developed and more practical model. It was shown that Janus nanoparticles may form dual polymer/particle interphase at polymer/polymer interface which can drastically affect the final mechanical properties of the system. Comparing the results of tensile tests imposed on different prepared samples with the predictions of the model proved its accuracy and reliability (error < 9%).
2019, 37(2): 178-188
doi: 10.1007/s10118-019-2180-9
Abstract:
This work is focused on simulating the rheological effects in polyamide. An experimental study is carried out in order to assess such features of polyamide as: the hysteretic behavior, the strain rate dependence, and the stress relaxation. The material response in tension is investigated. Digital images correlation method (DIC) is employed in order to measure the material compressibility. A newly developed constitutive model, which was previously used to simulate the mechanical response of polyethylene subjected to moderate strains and compressive loadings, is applied to capture the large strain, inelastic behavior of polyamide in tension. The gathered experimental data are utilized to determine the values of constitutive constants of viscoelasticity and plasticity, which describe the rheological properties of polyamide. The determined material parameters are included in the text. Different strategies for evaluating the material parameters are discussed. The proposed constitutive equation is implemented into the finite element (FE) system, ABAQUS, by taking advantage of the user subroutine UMAT, which allows to define custom material laws. Some exemplary FE simulations that were used to investigate the performance of the developed subroutine are described.
This work is focused on simulating the rheological effects in polyamide. An experimental study is carried out in order to assess such features of polyamide as: the hysteretic behavior, the strain rate dependence, and the stress relaxation. The material response in tension is investigated. Digital images correlation method (DIC) is employed in order to measure the material compressibility. A newly developed constitutive model, which was previously used to simulate the mechanical response of polyethylene subjected to moderate strains and compressive loadings, is applied to capture the large strain, inelastic behavior of polyamide in tension. The gathered experimental data are utilized to determine the values of constitutive constants of viscoelasticity and plasticity, which describe the rheological properties of polyamide. The determined material parameters are included in the text. Different strategies for evaluating the material parameters are discussed. The proposed constitutive equation is implemented into the finite element (FE) system, ABAQUS, by taking advantage of the user subroutine UMAT, which allows to define custom material laws. Some exemplary FE simulations that were used to investigate the performance of the developed subroutine are described.
2019, 37(2): 189-196
doi: 10.1007/s10118-019-2185-4
Abstract:
The SiO2 nanoparticles were coated on the surface of graphene oxide (GO) by sol-gel method to get the SiO2-G compound. The SiO2-G was restored and oleophylically modified to prepare hydrophobic modified SiO2-G (HM-SiO2-G) which was subsequently added to silicone rubber matrix to prepare two-component room temperature vulcanized (RTV-2) thermal conductive silicone rubber. The morphology, chemical structure and dispersity of the modified graphene were characterized with SEM, FTIR, Raman, and XPS methods. In addition, the heat-resistance behavior, mechanical properties, thermal conductivity, and electrical conductivity of the RTV-2 silicone rubber were also studied systematically. The results showed that the SiO2 nanoparticles were coated on graphene oxide successfully, and HM-SiO2-G was uniformly dispersed in RTV-2 silicone rubber. The addition of HM-SiO2-G could effectively improve the thermal stability, mechanical properties and thermal conductivity of RTV-2 silicone rubber and had no great influence on the electrical insulation performance.
The SiO2 nanoparticles were coated on the surface of graphene oxide (GO) by sol-gel method to get the SiO2-G compound. The SiO2-G was restored and oleophylically modified to prepare hydrophobic modified SiO2-G (HM-SiO2-G) which was subsequently added to silicone rubber matrix to prepare two-component room temperature vulcanized (RTV-2) thermal conductive silicone rubber. The morphology, chemical structure and dispersity of the modified graphene were characterized with SEM, FTIR, Raman, and XPS methods. In addition, the heat-resistance behavior, mechanical properties, thermal conductivity, and electrical conductivity of the RTV-2 silicone rubber were also studied systematically. The results showed that the SiO2 nanoparticles were coated on graphene oxide successfully, and HM-SiO2-G was uniformly dispersed in RTV-2 silicone rubber. The addition of HM-SiO2-G could effectively improve the thermal stability, mechanical properties and thermal conductivity of RTV-2 silicone rubber and had no great influence on the electrical insulation performance.
