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2017 Volume 35 Issue 8
2017, 35(8):
Abstract:
2017, 35(8): 909-923
doi: 10.1007/s10118-017-1952-3
Abstract:
Polyurethane micelles (PM)-based nanovehicles have shown great potential in targeted delivery of therapeutics and diagnostics into tumors. However, the pathways of PMs entering cancer cells and the action mechanism of targeting ligands have yet to be understood. In this contribution, the actively-targeted PM were developed using trastuzumab as a model targeting group. It was found that PM were mainly taken up by SKOV-3 tumor cells via a micropinocytosis process, while the incorporation of trastuzumab to PM enabled a receptor-mediated endocytosis of nanocarriers in cancer cells, leading to more efficient cell entry and enhanced anticancer efficacy of chemotherapeutic drugs both in vitro and in vivo. This study is advantageous to the understanding of the action mechanism of trastuzumab, and significant for the construction of improved formulations for targeted delivery and precise therapy.
Polyurethane micelles (PM)-based nanovehicles have shown great potential in targeted delivery of therapeutics and diagnostics into tumors. However, the pathways of PMs entering cancer cells and the action mechanism of targeting ligands have yet to be understood. In this contribution, the actively-targeted PM were developed using trastuzumab as a model targeting group. It was found that PM were mainly taken up by SKOV-3 tumor cells via a micropinocytosis process, while the incorporation of trastuzumab to PM enabled a receptor-mediated endocytosis of nanocarriers in cancer cells, leading to more efficient cell entry and enhanced anticancer efficacy of chemotherapeutic drugs both in vitro and in vivo. This study is advantageous to the understanding of the action mechanism of trastuzumab, and significant for the construction of improved formulations for targeted delivery and precise therapy.
2017, 35(8): 924-938
doi: 10.1007/s10118-017-1947-0
Abstract:
Well-defined pH-responsive poly(ε-caprolactone)-graft-β-cyclodextrin-graft-poly(2-(dimethylamino)ethyl-methacrylate)-co-poly(ethylene glycol) methacrylate amphiphilic copolymers (PCL-g-β-CD-g-P(DMAEMA-co-PEGMA)) were synthesized using a combination of atom transfer radical polymerization (ATRP), ring opening polymerization (ROP) and "click" chemistry. Successful synthesis of polymers was confirmed by Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H-NMR), and gel permeation chromatography (GPC). Then, the polymers could self-assemble into micelles in aqueous solution, which was demonstrated by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The pH-responsive self-assembly behavior of these copolymers in water was investigated at different pH values of 7.4 and 5.0 for controlled doxorubicin (DOX) release, and these results revealed that the release rate of DOX could be effectively controlled by altering the pH, and the release of drug loading efficiency (DLE) was up to 88% (W/W). CCK-8 assays showed that the copolymers had low toxicity and possessed good biodegradability and biocompatibility, whereas the DOX-loaded micelles remained with high cytotoxicity for HeLa cells. Moreover, confocal laser scanning microscopy (CLSM) images revealed that polymeric micelles could actively target the tumor site and the efficient intracellular DOX release from polymeric micelles toward the tumor cells further confirmed the anti-tumor effect. The DOX-loaded micelles could easily enter the cells and produce the desired pharmacological action and minimize the side effect of free DOX. These results successfully indicated that pH-responsive polymeric micelles could be potential hydrophobic drug delivery carriers for cancer targeting therapy with sustained release.
Well-defined pH-responsive poly(ε-caprolactone)-graft-β-cyclodextrin-graft-poly(2-(dimethylamino)ethyl-methacrylate)-co-poly(ethylene glycol) methacrylate amphiphilic copolymers (PCL-g-β-CD-g-P(DMAEMA-co-PEGMA)) were synthesized using a combination of atom transfer radical polymerization (ATRP), ring opening polymerization (ROP) and "click" chemistry. Successful synthesis of polymers was confirmed by Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H-NMR), and gel permeation chromatography (GPC). Then, the polymers could self-assemble into micelles in aqueous solution, which was demonstrated by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The pH-responsive self-assembly behavior of these copolymers in water was investigated at different pH values of 7.4 and 5.0 for controlled doxorubicin (DOX) release, and these results revealed that the release rate of DOX could be effectively controlled by altering the pH, and the release of drug loading efficiency (DLE) was up to 88% (W/W). CCK-8 assays showed that the copolymers had low toxicity and possessed good biodegradability and biocompatibility, whereas the DOX-loaded micelles remained with high cytotoxicity for HeLa cells. Moreover, confocal laser scanning microscopy (CLSM) images revealed that polymeric micelles could actively target the tumor site and the efficient intracellular DOX release from polymeric micelles toward the tumor cells further confirmed the anti-tumor effect. The DOX-loaded micelles could easily enter the cells and produce the desired pharmacological action and minimize the side effect of free DOX. These results successfully indicated that pH-responsive polymeric micelles could be potential hydrophobic drug delivery carriers for cancer targeting therapy with sustained release.
2017, 35(8): 939-949
doi: 10.1007/s10118-017-1955-0
Abstract:
Ethylene-α-octene copolymer (POE)/polystyrene (PS) blend pellets with fine particle sizes were prepared by diffusion and subsequent polymerization of styrene in POE pellets through a one-pot procedure. The effects of the amounts of styrene and BPO on PS content, monomer efficiency and monomer conversion were investigated. The blend pellets were characterized by Micro-FTIR and FESEM, showing homogeneous diametrical distributions of PS and particle size. After melt-processing into rods, the average particle sizes are almost doubled, but still in submicron scale. Compared to neat POE rods, the blend rods with PS content higher than 15% exhibit improved tensile modulus and tensile strength without significantly losing ductility, being attributed to the small sizes, complex nature of particles and the existence of POE-g-PS copolymer that result in good interfacial adhesion. POE/PS pellets were compared with the previously reported PP/PS pellets, and the differences between the two systems are attributed to the different morphology of the two matrices:POE is completely amorphous at the diffusion and polymerization temperature, while iPP is semicrystalline. Without efficient impediment of the crystal lamellae in POE pellets, styrene diffuses easily in POE pellets.
Ethylene-α-octene copolymer (POE)/polystyrene (PS) blend pellets with fine particle sizes were prepared by diffusion and subsequent polymerization of styrene in POE pellets through a one-pot procedure. The effects of the amounts of styrene and BPO on PS content, monomer efficiency and monomer conversion were investigated. The blend pellets were characterized by Micro-FTIR and FESEM, showing homogeneous diametrical distributions of PS and particle size. After melt-processing into rods, the average particle sizes are almost doubled, but still in submicron scale. Compared to neat POE rods, the blend rods with PS content higher than 15% exhibit improved tensile modulus and tensile strength without significantly losing ductility, being attributed to the small sizes, complex nature of particles and the existence of POE-g-PS copolymer that result in good interfacial adhesion. POE/PS pellets were compared with the previously reported PP/PS pellets, and the differences between the two systems are attributed to the different morphology of the two matrices:POE is completely amorphous at the diffusion and polymerization temperature, while iPP is semicrystalline. Without efficient impediment of the crystal lamellae in POE pellets, styrene diffuses easily in POE pellets.
2017, 35(8): 950-960
doi: 10.1007/s10118-017-1948-z
Abstract:
The use of proteins as therapeutics in nanomedicine is an emerging research field and has developed rapidly. However, proteins are always vulnerable to renal excretion or digestion by the proteolytic system in vivo, which limits their usage to a large extent. Although biocompatible polymers have been covalently linked to proteins to protect them from recognition by the immune system and prolong their circulation time, the biological activity of them is sometimes decreased. To fill this gap, physical isolation, wrapping, or encapsulation techniques are employed. Up to now, various mature examples were reported, but the whole time scales for guest molecules loading and releasing, especially the initial rapid loading process, were rarely mentioned. Herein, a series of dual-responsive poly(N-isopropylacrylamide-co-methacrylic acid) (P(NIPAM-co-MAA)) microgels were synthesized and employed to investigate the kinetics of in situ complexation and release of lysozyme under external stimuli modulation upon a stopped-flow apparatus, which was suitable for rapid dynamic monitoring. Close inspection of the adsorption kinetics during the early stages (<50 s) revealed that the initial microgel collapse occurred within~1 s, with more rapid transitions being observed when higher lysozyme concentrations were targeted. All the dynamic traces could be well fitted with a double exponential function, suggesting a fast (τ1) and a slow (τ2) relaxation time, respectively. Then, the kinetics of releasing bound lysozyme from microgels was carried on by utilizing the pH-responsive property, and the evaluation of the activity of released lysozyme was synchronously measured in a Micrococcus lysodeikticus (M. lysodeikticus) cell suspension. The corresponding relaxation time (τ) was also calculated by fitting the recorded dynamic traces. We speculate that this work can provide basic dynamics data and theoretical basis for microgels based nanocarriers to be used for protein delivery, controlled release, and possible chemical separation.
The use of proteins as therapeutics in nanomedicine is an emerging research field and has developed rapidly. However, proteins are always vulnerable to renal excretion or digestion by the proteolytic system in vivo, which limits their usage to a large extent. Although biocompatible polymers have been covalently linked to proteins to protect them from recognition by the immune system and prolong their circulation time, the biological activity of them is sometimes decreased. To fill this gap, physical isolation, wrapping, or encapsulation techniques are employed. Up to now, various mature examples were reported, but the whole time scales for guest molecules loading and releasing, especially the initial rapid loading process, were rarely mentioned. Herein, a series of dual-responsive poly(N-isopropylacrylamide-co-methacrylic acid) (P(NIPAM-co-MAA)) microgels were synthesized and employed to investigate the kinetics of in situ complexation and release of lysozyme under external stimuli modulation upon a stopped-flow apparatus, which was suitable for rapid dynamic monitoring. Close inspection of the adsorption kinetics during the early stages (<50 s) revealed that the initial microgel collapse occurred within~1 s, with more rapid transitions being observed when higher lysozyme concentrations were targeted. All the dynamic traces could be well fitted with a double exponential function, suggesting a fast (τ1) and a slow (τ2) relaxation time, respectively. Then, the kinetics of releasing bound lysozyme from microgels was carried on by utilizing the pH-responsive property, and the evaluation of the activity of released lysozyme was synchronously measured in a Micrococcus lysodeikticus (M. lysodeikticus) cell suspension. The corresponding relaxation time (τ) was also calculated by fitting the recorded dynamic traces. We speculate that this work can provide basic dynamics data and theoretical basis for microgels based nanocarriers to be used for protein delivery, controlled release, and possible chemical separation.
2017, 35(8): 961-973
doi: 10.1007/s10118-017-1957-y
Abstract:
Flexible electrochemical capacitors (ECs) are vitally important as the emerging flexible electronics. We have prepared polypyrrole doped with counter ion of Cl- on carbon fibers (PPy-Cl/CFs) via the simple electrochemical deposition method. The flexible ECs based on PPy-Cl/CFs electrodes have been assembled by using H3PO4/poly(vinyl alcohol) (PVA), H2SO4/PVA, LiClO4/PVA, KCl/PVA and LiCl/PVA as gel electrolytes. The capacitive properties of ECs have been systematically evaluated with electrochemical methods. The results show that the cells with H3PO4/PVA electrolyte exhibit good cyclic stability (91.5% retention after 15000 cycles) although PPy-Cl/CFs has moderate specific capacitance in H3PO4/PVA (41.6 mF·cm-1 or 52.0 F·cm-3). However, the ECs in other electrolytes have poor cyclic stability. Further electrochemical analysis reveals that the doping/dedoping processes of PPy-Cl/CFs are different in the five electrolytes, and X-ray photoelectron spectra demonstrate that the ratios of counter anions in PPy's oxidized states to those in reduced states are obviously different when PPy-Cl/CFs are kept in reduced or oxidized states in the five electrolytes. The results also illustrate why the capacitors using H3PO4/PVA as electrolyte exhibit good cyclic stability. Furthermore, a light emitting diode (LED) with a threshold voltage of 2.5 V can be lighted by three ECs connected in series.
Flexible electrochemical capacitors (ECs) are vitally important as the emerging flexible electronics. We have prepared polypyrrole doped with counter ion of Cl- on carbon fibers (PPy-Cl/CFs) via the simple electrochemical deposition method. The flexible ECs based on PPy-Cl/CFs electrodes have been assembled by using H3PO4/poly(vinyl alcohol) (PVA), H2SO4/PVA, LiClO4/PVA, KCl/PVA and LiCl/PVA as gel electrolytes. The capacitive properties of ECs have been systematically evaluated with electrochemical methods. The results show that the cells with H3PO4/PVA electrolyte exhibit good cyclic stability (91.5% retention after 15000 cycles) although PPy-Cl/CFs has moderate specific capacitance in H3PO4/PVA (41.6 mF·cm-1 or 52.0 F·cm-3). However, the ECs in other electrolytes have poor cyclic stability. Further electrochemical analysis reveals that the doping/dedoping processes of PPy-Cl/CFs are different in the five electrolytes, and X-ray photoelectron spectra demonstrate that the ratios of counter anions in PPy's oxidized states to those in reduced states are obviously different when PPy-Cl/CFs are kept in reduced or oxidized states in the five electrolytes. The results also illustrate why the capacitors using H3PO4/PVA as electrolyte exhibit good cyclic stability. Furthermore, a light emitting diode (LED) with a threshold voltage of 2.5 V can be lighted by three ECs connected in series.
Effect of Star-shaped Chain Architectures on the Polylactide Stereocomplex Crystallization Behaviors
2017, 35(8): 974-991
doi: 10.1007/s10118-017-1935-4
Abstract:
Linear and star-shaped polylactides (PLA) with similar molecular weights of each arm are synthesized via ring-opening polymerization of LA with 3-butyn-1-ol and pentaerythritol as initiators, respectively. By solution blending of equivalent mass of poly(L-lactic acid)s (PLLAs) and poly(D-lactic acid)s (PDLAs), perfect PLA stereocomplexes (scPLAs) are prepared and confirmed by WAXD and FTIR analysis. Effect of chain architectures on stereocomplex crystallization is investigated by studying the non-isothermal and isothermal crystallization of linear and star-shaped polylactide stereocomplexes. In dynamic DSC and POM test, star-shaped PLLA (4sPLLA)/PDLA and PLLA/star-shaped PDLA (4sPDLA) stereocomplexes reach rapid crystallization and higher crystallinity due to larger spherulite density of star-shaped chain and excellent chain mobility of linear chain. In isothermal crystallization test, much faster crystallization and less crystallization half-time is obtained with the increase of star-shaped chain. Meanwhile, 4sPLLA/PDLA and PLLA/4sPDLA are found to have the highest crystallinity, suggesting limitation of too much star-shaped chain for 4sPLLA/4sPDLA and restriction of linear chain in nucleation capacity for PLLA/PDLA. The results reveal that star-shaped chain has an important influence on the crystallization of scPLAs.
Linear and star-shaped polylactides (PLA) with similar molecular weights of each arm are synthesized via ring-opening polymerization of LA with 3-butyn-1-ol and pentaerythritol as initiators, respectively. By solution blending of equivalent mass of poly(L-lactic acid)s (PLLAs) and poly(D-lactic acid)s (PDLAs), perfect PLA stereocomplexes (scPLAs) are prepared and confirmed by WAXD and FTIR analysis. Effect of chain architectures on stereocomplex crystallization is investigated by studying the non-isothermal and isothermal crystallization of linear and star-shaped polylactide stereocomplexes. In dynamic DSC and POM test, star-shaped PLLA (4sPLLA)/PDLA and PLLA/star-shaped PDLA (4sPDLA) stereocomplexes reach rapid crystallization and higher crystallinity due to larger spherulite density of star-shaped chain and excellent chain mobility of linear chain. In isothermal crystallization test, much faster crystallization and less crystallization half-time is obtained with the increase of star-shaped chain. Meanwhile, 4sPLLA/PDLA and PLLA/4sPDLA are found to have the highest crystallinity, suggesting limitation of too much star-shaped chain for 4sPLLA/4sPDLA and restriction of linear chain in nucleation capacity for PLLA/PDLA. The results reveal that star-shaped chain has an important influence on the crystallization of scPLAs.
2017, 35(8): 992-1000
doi: 10.1007/s10118-017-1937-2
Abstract:
In this work, the effect of dioctadecyl dimethyl ammonium chloride (DDAC, a kind of alkyl ammonium salt) on polar β phase content and the diameter of electrospun PVDF nanofibers was investigated for the first time. Our experimental results show that the diameter of the electrospun PVDF nanofiber could be largely reduced and the content of polar β phase also become dominant immediately by just adding a little amount of DDAC. When the mass fraction of DDAC reached 4%, the content of polar β phase increased by about 39.1% compared with PVDF nanofibers without DDAC. Besides, the crystallinity of PVDF nanofibers also increased with the addition of DDAC. Based on the results, the possible mechanism of cooperative effect between electrospinning and DDAC on fiber diameter and formation of β phase in PVDF was discussed.
In this work, the effect of dioctadecyl dimethyl ammonium chloride (DDAC, a kind of alkyl ammonium salt) on polar β phase content and the diameter of electrospun PVDF nanofibers was investigated for the first time. Our experimental results show that the diameter of the electrospun PVDF nanofiber could be largely reduced and the content of polar β phase also become dominant immediately by just adding a little amount of DDAC. When the mass fraction of DDAC reached 4%, the content of polar β phase increased by about 39.1% compared with PVDF nanofibers without DDAC. Besides, the crystallinity of PVDF nanofibers also increased with the addition of DDAC. Based on the results, the possible mechanism of cooperative effect between electrospinning and DDAC on fiber diameter and formation of β phase in PVDF was discussed.
2017, 35(8): 1001-1008
doi: 10.1007/s10118-017-1984-8
Abstract:
Core-shell nanofibers were prepared by coaxial electrospinning technology, with poly(ethylene oxide) (PEO) as the core while poly(acrylic acid) (PAA) as the shell. PEO and PAA can form polymer complexes based on hydrogen bonding. In order to avoid forming strong hydrogen bonding complexes at nozzle and blocking spinning process, a polar aprotic solvent, N, N-dimethylformamide (DMF), was selected to dissolve PEO and PAA respectively. SEM, TEM and DSC were utilized to characterize the morphology and structure of PEO-PAA core-shell nanofibers. FTIR spectra demonstrated that hydrogen bonding was formed at the core-shell interface. In addition, the PAA shell of the nanofibers can be cross-linked by ethylene glycol (EG) under heat treatment, which increases the stability and extends the potential applications in aqueous environment.
Core-shell nanofibers were prepared by coaxial electrospinning technology, with poly(ethylene oxide) (PEO) as the core while poly(acrylic acid) (PAA) as the shell. PEO and PAA can form polymer complexes based on hydrogen bonding. In order to avoid forming strong hydrogen bonding complexes at nozzle and blocking spinning process, a polar aprotic solvent, N, N-dimethylformamide (DMF), was selected to dissolve PEO and PAA respectively. SEM, TEM and DSC were utilized to characterize the morphology and structure of PEO-PAA core-shell nanofibers. FTIR spectra demonstrated that hydrogen bonding was formed at the core-shell interface. In addition, the PAA shell of the nanofibers can be cross-linked by ethylene glycol (EG) under heat treatment, which increases the stability and extends the potential applications in aqueous environment.
2017, 35(8): 1009-1019
doi: 10.1007/s10118-017-1942-5
Abstract:
Differential fast scanning calorimetry (DFSC) was employed on the study of self-nucleation behavior of poly(butylene succinate) (PBS). The ultra-fast cooling ability of DFSC allows investigating the effect of self-nucleation on the isothermal crystallization kinetics over a wide temperature range. Crystallization half-time, instead of crystallization peak temperature, was used to describe the self-nucleation behavior, and the self-nucleation domain for the samples crystallized at different temperatures was determined. Due to the competition between homogenous nucleation and self-nuclei, the effect of self-nucleation was less pronounced at high supercooling than that for the sample isothermally crystallized at higher temperature. An efficiency scale to judge the efficiency of nucleating agents from the crystallization half-time was also introduced in this work.
Differential fast scanning calorimetry (DFSC) was employed on the study of self-nucleation behavior of poly(butylene succinate) (PBS). The ultra-fast cooling ability of DFSC allows investigating the effect of self-nucleation on the isothermal crystallization kinetics over a wide temperature range. Crystallization half-time, instead of crystallization peak temperature, was used to describe the self-nucleation behavior, and the self-nucleation domain for the samples crystallized at different temperatures was determined. Due to the competition between homogenous nucleation and self-nuclei, the effect of self-nucleation was less pronounced at high supercooling than that for the sample isothermally crystallized at higher temperature. An efficiency scale to judge the efficiency of nucleating agents from the crystallization half-time was also introduced in this work.
2017, 35(8): 1020-1034
doi: 10.1007/s10118-017-1945-2
Abstract:
Polyacrylonitrile (PAN) polymers with different compositions were prepared by an efficient aqueous free-radical polymerization technique. Thermal properties of polyacrylonitrile homopolymer (PAN), poly(acrylonitrile/itaconic acid)[P(AN/IA)] and poly(acrylonitrile/itaconic acid/acrylamide)[P(AN/IA/AM)] were studied by Fourier transform infrared spectroscopy, X-ray diffraction, differential scanning calorimetry and thermogravimetry in detail. It was found that AM had the ability to initiate and accelerate thermal oxidative stabilization process, which was confirmed by the lower initiation temperature and broader exothermic peak in P(AN/IA/AM) as compared with that in P(AN/IA) and PAN. The intensity of heat releasing during the thermal treatment was relaxed due to the presence of two separated exothermic peaks. Accompanied by DSC analysis and calculation of the apparent activation energy of cyclization reaction, two peaks were assigned to the ionic and free radical induction mechanisms, respectively. The higher rate constant in P(AN/IA/AM) indicated that the ionic mechanism actually had a kinetic advantage at promoting thermal stability over the free radical mechanism. This study clearly show that the synthesized P(AN/IA/AM) terpolymers possess larger room to adjust manufacture parameters to fabricate high performance of PAN-based carbon fibers.
Polyacrylonitrile (PAN) polymers with different compositions were prepared by an efficient aqueous free-radical polymerization technique. Thermal properties of polyacrylonitrile homopolymer (PAN), poly(acrylonitrile/itaconic acid)[P(AN/IA)] and poly(acrylonitrile/itaconic acid/acrylamide)[P(AN/IA/AM)] were studied by Fourier transform infrared spectroscopy, X-ray diffraction, differential scanning calorimetry and thermogravimetry in detail. It was found that AM had the ability to initiate and accelerate thermal oxidative stabilization process, which was confirmed by the lower initiation temperature and broader exothermic peak in P(AN/IA/AM) as compared with that in P(AN/IA) and PAN. The intensity of heat releasing during the thermal treatment was relaxed due to the presence of two separated exothermic peaks. Accompanied by DSC analysis and calculation of the apparent activation energy of cyclization reaction, two peaks were assigned to the ionic and free radical induction mechanisms, respectively. The higher rate constant in P(AN/IA/AM) indicated that the ionic mechanism actually had a kinetic advantage at promoting thermal stability over the free radical mechanism. This study clearly show that the synthesized P(AN/IA/AM) terpolymers possess larger room to adjust manufacture parameters to fabricate high performance of PAN-based carbon fibers.
2017, 35(8): 1035-1042
doi: 10.1007/s10118-017-1950-5
Abstract:
Optically active and inactive hyperbranched polymers with specific thermoresponsive behaviours in water were reported. Through two steps hyperbranched polyethylenimine (HPEI) polymers terminated with different amount of D-phenylalanine (D-Phe), L-phenylalanine (L-Phe) or DL-phenylalanine (DL-Phe) were prepared and characterized. The analyses on the solution properties by turbidimetry, dynamic light scattering, fluorescence probe and 1H-NMR demonstrated that all the polymers exhibited specific thermoresponsive behaviours in water, including:(1) In the dilute polymer concentration region, increasing the polymer concentration led to the increase of phase transition temperature; (2) The optically inactive thermoresponsive hyperbranched polymers showed a higher cloud-point temperature (Tcp) than their corresponding optically active ones in a relatively higher polymer concentration; (3) At the same polymer concentration the hydrophobic groups of the optically inactive HPEI-DL-Phe formed more perfect hydrophobic domain than those of the optically active HPEI-L-Phe and HPEI-D-Phe.
Optically active and inactive hyperbranched polymers with specific thermoresponsive behaviours in water were reported. Through two steps hyperbranched polyethylenimine (HPEI) polymers terminated with different amount of D-phenylalanine (D-Phe), L-phenylalanine (L-Phe) or DL-phenylalanine (DL-Phe) were prepared and characterized. The analyses on the solution properties by turbidimetry, dynamic light scattering, fluorescence probe and 1H-NMR demonstrated that all the polymers exhibited specific thermoresponsive behaviours in water, including:(1) In the dilute polymer concentration region, increasing the polymer concentration led to the increase of phase transition temperature; (2) The optically inactive thermoresponsive hyperbranched polymers showed a higher cloud-point temperature (Tcp) than their corresponding optically active ones in a relatively higher polymer concentration; (3) At the same polymer concentration the hydrophobic groups of the optically inactive HPEI-DL-Phe formed more perfect hydrophobic domain than those of the optically active HPEI-L-Phe and HPEI-D-Phe.
