Random Copolymer Poly Research Articles

Effect of chain microstructure on self-assembly and emulsification of amphiphilic poly(acrylic acid)-polystyrene copolymers.

In this study, a series of random copolymer poly(acrylic acid-co-styrene) (P(AA-co-St)) and block copolymer poly(acrylic acid)-b-polystyrene (PAA-b-PSt) with similar chemical composition but different chain microstructure were synthesized. The self-assembly behavior of random and block copolymers in selective solvent was investigated, and the structural evaluation of random and block copolymers micelles was carried out by transmission electron microscopy (TEM), dynamic light scattering (DLS) measurement, and X-ray photoelectron spectroscopy (XPS). Moreover, together with experimental characterization, the theoretical method dissipative particle dynamics (DPD) approach was applied to investigate the morphological structures of micelles composed from random and block copolymers. Results revealed that the structure of polymeric micelles is significantly affected by the distribution sequence of hydrophilic and hydrophobic monomers in copolymer chains. Furthermore, polymeric micelles based on P(AA-co-St) and PAA-b-PSt with about 50 mol% hydrophilic composition were chosen as the model to investigate the influence of micellar structure on emulsifying performance. For PAA-b-PSt micelles (B48), stable water-in-oil (w/o) emulsions could only obtained when the pH values were lower than 5. As a comparison, the P(AA-co-St) micelles (R49) had an excellent emulsification performance at 4-10 pH, and the pH-induced phase inversion derived from obtained emulsions observed at pH higher than 6. Preliminary results confirm that the micellar structure controlled by chain microstructure plays an important role in the interface behavior of polymer micelles. Compared with PAA-b-PSt micelles, P(AA-co-St) micelles have better interfacial performance and are more tailorable and controllable; thus they can be used as a model for further study of polymeric particulate emulsifiers. This paper provides new insight into the principles governing extremely high emulsifying efficiency of polymeric particulate emulsifiers and pH-responsive properties of the formed emulsions.

One-step formation of multiple Pickering emulsions stabilized by self-assembled poly(dodecyl acrylate-co-acrylic acid) nanoparticles.

In this study, a one-step generation of stable multiple Pickering emulsions using pH-responsive polymeric nanoparticles as the only emulsifier was reported. The polymeric nanoparticles were self-assembled from an amphiphilic random copolymer poly(dodecyl acrylate-co-acrylic acid) (PDAA), and the effect of the copolymer content on the size and morphology of PDAA nanoparticles was determined by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The emulsification study of PDAA nanoparticles revealed that multiple Pickering emulsions could be generated through a one-step phase inversion process by using PDAA nanoparticles as the stabilizer. Moreover, the emulsification performance of PDAA nanoparticles at different pH values demonstrated that multiple emulsions with long-time stability could only be stabilized by PDAA nanoparticles at pH 5.5, indicating that the surface wettability of PDAA nanoparticles plays a crucial role in determining the type and stability of the prepared Pickering emulsions. Additionally, the polarity of oil does not affect the emulsification performance of PDAA nanoparticles, and a wide range of oils could be used as the oil phase to prepare multiple emulsions. These results demonstrated that multiple Pickering emulsions could be generated via the one-step emulsification process using self-assembled polymeric nanoparticles as the stabilizer, and the prepared multiple emulsions have promising potential to be applied in the cosmetic, medical, and food industries.

A facile preparation of pH‐temperature dual stimuli‐responsive supramolecular hydrogel and its controllable drug release

ABSTRACTA series of pH‐temperature dual stimuli‐responsive random copolymers poly[N,N‐dimethylaminoethyl methacrylate‐co‐poly(poly(ethylene glycol) methyl ether methacrylate][poly(DMAEMA‐co‐MPEGMA)] were synthesized by free radical polymerization. The supramolecular hydrogel was formed by pseudopolyrotaxane, which was prepared with the host‐guest interactions between α‐cyclodextrin (α‐CD) and poly(ethylene glycol) (PEG) side chains. Fourier transform infrared (FT‐IR), nuclear magnetic resonance (1H NMR), and X‐ray diffraction (XRD) confirmed the structures of the hydrogels. The pH‐temperature dual stimuli responsive properties of the hydrogels were characterized by rheometer. Finally, the controllable drug release behavior of the hydrogel, which was used 5‐fluorouracil (5‐Fu) as the model drug, was investigated at different temperatures and different pH values. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43279.

Fabrication and Characterization of Cotton Fabrics with Grafted Thermo-Responsive Random Copolymer Poly(2-(2-methoxyethoxy) Ethoxyethyl Methacrylate-co-Acrylic Acid)

The cotton fabrics with enhanced cleaning capability were prepared by grafting thermo-responsive random copolymer poly (2-(2-methoxyethoxy) ethoxyethyl methacrylate-co-acrylic acid), abbreviated as P(MEO2MA-co-AA), to the amino modified cotton fabrics. ATR-FTIR measurement confirmed the immobilization of P(MEO2MA-co-AA) to the cotton fabrics. Equilibrium swelling ratio indicates that the cotton fabric with grafted P(MEO2MA-co-AA) possesses thermo-responsive ability .The enhanced cleaning capability was investigated by the decontamination experiments probed with confocal microscope. The results show the cleaning capability can be prominently improved when the cleaning temperature is lower than the LCST of P(MEO2MA-co-AA).

The Swelling and Transition Behavior of Poly(2-(2-methoxyethoxy) Ethoxyethyl Methacrylate-co-Ethylene Glycol Methacrylate) Random Copolymers in Thin Films

Thermo-responsive random copolymer poly (2-(2-methoxyethoxy) ethoxyethyl methacrylate-co-ethylene glycol methacrylate) P(MEO2MA-co-EGMA) was investigated in thin film. By spin-coating, the obtained film thickness varied from 9 nm to 97 nm, which shows a linear relationship with tetrahydrofuran solution concentration. The swelling and transition behavior of P(MEO2MA-co-EGMA) films were monitored by white-light interferometry under water vapor atmosphere. It is observed that the film rapidly swelled in the first 90 min. Afterwards it reached an equilibrium state. The film thickness did not show a prominent increase by further prolonging the swelling time. In addition, the swelling capability of P(MEO2MA-co-EGMA) films was related to the film thickness. The thicker film possessed less swelling capability. Unlike the transition behavior in aqueous solution, P(MEO2MA-co-EGMA) films showed a much broader transition region, which might be related to the influence of Si substrate.

Enhancing the conductivity of carbon nanotube filled blends by tuning their phase separated morphology with a copolymer

We describe an approach to engineer bi-continuous conductive blends of polymers and multiwall carbon nanotubes (MWNTs) by formation of a percolating network of MWNTs in one phase of the blend. Thereto, spinodal decomposition combined with compatibilization by an interfacially segregated random copolymer (rcp) is proposed. A systematic study of the effect of the concentration of the random copolymer poly(styrene-random-methyl methacrylate) (PS-r-PMMA) on the electrical conductivity of a phase separating poly[(α-methyl styrene)-co-acrylonitrile]/poly(methyl methacrylate) (PαMSAN/PMMA) blend with MWNTs was performed above the spinodal temperature (at 220 °C) and at room temperature. Compatibilization results in a huge conductivity increase, whereby blends with 0.5 wt% MWNTs and 0.25 wt% copolymer exhibit the same conductivity as percolating bi-phasic blends with 2 wt% MWNTs. In addition, the linear viscoelastic moduli show a power law increase with the concentration of copolymer. It was deduced that the observed increase in conductivity was caused by a substantial morphology refinement and increased degree of cocontinuity after copolymer addition leading to the formation of double percolated networks in the blends. These findings were corroborated with optical micrographs and scanning transmission electron microscopy (STEM) images for blends with 0.5 wt% and 2 wt% carbon nanotubes, respectively. The morphology changes can be explained by an interfacial tension reduction, which alters structure dynamics during annealing. The effectiveness of the long random copolymer in compatibilizing the blend is attributed to multiple interface crossings coupled with the ability of the copolymer blocks to anchor into the homopolymers. This simple approach can provide a pathway to develop low cost and ubiquitous high performance dielectric materials with ultra-low percolation thresholds.

Multifunctional copolymer coating of polyethylene glycol, glycidyl methacrylate, and REDV to enhance the selectivity of endothelial cells

Multifunctional polymer coatings have potential applications in biomaterials. These coatings possess reactive functional groups for the immobilization of specific biological factors that can influence cellular behavior. These coatings also display low nonspecific protein adsorption. In this study, we prepared a multifunctional polymer coating through the deposition of random copolymers of poly(ethylene glycol) methacrylate (PEGMA) and glycidyl methacrylate (GMA) to prevent nonspecific attachment and enable the covalence of Arg–Glu–Asp–Val (REDV) peptide with endothelial cells (ECs) selectivity. Coatings were characterized by X-ray photoelectron spectroscopy (XPS). The adhesion and proliferation of ECs and smooth muscle cells (SMCs) onto the REDV-modified surface were investigated to understand the synergistic action of antifouling PEG and EC selective REDV peptide conjugated GMA. The copolymers containing GMA and PEG groups are very useful as a multifunctional coating material with anti-fouling and ECs specific adhesion for implant materials surface modification.

Effect of incorporating bis(2-hydroxyethyl) terephthalate on thermal and mechanical properties and degradability of poly(butylene succinate)

A series of novel random copolymers of poly(butylene succinate-co-ethylene terephthalate) were synthesized and characterized in terms of thermal and mechanical properties, crystallinity and biodegradability. The composition and microstructure of the prepared copolyesters were characterized by 1H NMR and 13C NMR, respectively. It was seen that the PBS sequence length decreases with ethylene terephthalate content. All copolymers are semi-crystalline and crystallinity and crystallite size decrease slightly with the comonomer content up to 10%, but the introduction of 20% comonomer leads to decrease the crystallinity up to 29%. The melting temperature of copolyesters decreases with the comonomer content according to the Baur’s equation that indicates only PBS blocks crystallize and crystallite size is decreased with the comonomer content. It was also investigated that the elastic modulus also decreases slightly with the comonomer content. However, the elongation at break increases by 500% due to the decrease in crystallite size and crystallinity. Incorporating non-biodegradable aromatic comonomer has a little effect on copolyester degradability because of the randomness and lower crystallite size. Open image in new window

Electrospun polymer nanofibers of P(NIPAAm-co-SA-co-FBPY): Preparation, structural control, metal ion sensing and thermoresponsive characteristics

Multifunctional electrospun (ES) nanofibers prepared from random copolymers of poly{(N-isopropylacrylamide)-co-(stearyl acid)-co-[9,9-dihexylfluorene-2-bipyridine-7-(4-vinylphenyl)]} (poly(NIPAAm-co-SA-co-FBPY) were successfully prepared from the electrospinning technique with a single-capillary spinneret. FBPY demonstrated blue or red shift in emission wavelength and fluorescence quenching when chelating with different metal ions. With appropriate composition of SA in the copolymer, films and nanofibers could maintain their morphology in aqueous solution at different thermal treatments. Polymers in three states, solution, film and nanofiber, were prepared and their effects on sensing ability were investigated. The smooth nanofibers prepared from P2 (with copolymer composition of NIPAAm:SA:FBPY = 93:6:1) demonstrated superior sensitivity as low as 10−5 M in sensing zinc ions as compared to polymer films (10−3 M) due to the high specific surface area of nanofibers. The porous nanofibers of P2 were also manufactured to further enhance sensing performance and showed the best sensitivity (10−6 M) among three states when sensing with zinc ions (sensitivity of polymer solution in THF was about 10−5 M). These nanofibers also exhibit an interesting “on/off” switch behavior with decreasing temperature from 40 to 10 °C due to the hydrophobic–hydrophilic transition of NIPAAm moieties which cause the gradual swelling of nanofibers. These results indicated that the new nanofibers could have potential applications in multifunctional sensory devices.

Determination of phthalates in food packing materials by electrokinetic chromatography with polymeric pseudostationary phase

Polymeric pseudostationary phase (PSP), formed by random copolymer poly (stearyl methacrylate-co-methacrylic acid) (P(SMA-co-MAA)), was used in electrokinetic chromatography (EKC) to separate 15 kinds of phthalates (PAEs). The organic solvent modifier is a key factor for the separation of PAEs. Without organic solvents, only four kinds of PAEs with smaller molecular weight could be separated in the running buffer containing 1% P(SMA-co-MAA). The other eleven kinds of PAEs with larger molecular weight could be separated within 25min by adding 40% (v/v) methanol and 2% (v/v) 1-butanol in the running buffer. The linear ranges of 15 kinds of PAEs were between 2 and 200mg/L, and the limit of detection based on the ratio of signal to noise of 3 were between 1 and 3mg/L. The method was applied to determination of PAEs in 6 kinds of food packing materials. The recoveries were between 81% and 118% with the RSD less than 4%.

New eco-friendly random copolyesters based on poly(propylene cyclohexanedicarboxylate): Structure-properties relationships

A series of novel random copolymers of poly(propylene 1,4-cyclohexanedicarboxylate) (PPCE) containing neo - pentyl glycol sub-unit (P(PCExNCEy)) were synthesized and characterized in terms of molecular and solid-state properties. In addition, biodegradability studies in compost have been conducted. The copolymers displayed a high and similar thermal stability with respect to PPCE. At room temperature, all the copoly- mers appeared as semicrystalline materials: the main effect of copolymerization was a lowering of crystallinity degree (!c) and a decrease of the melting temperature compared to the parent homopolymer. In particular, Wide Angle X-Ray diffrac- tion (WAXD) measurements indicated that P(PCExNCEy) copolymers are characterized by cocrystallization, PNCE co- units cocrystallizing in PPCE crystalline phase. Final properties and biodegradation rate of the materials under study were strictly dependent on copolymer composition and !c. As a matter of fact, the elastic modulus and the elongation at break decreased and increased, respectively, as neopentyl glycol cyclohexanedicarboxylate (NCE) unit content was increased. The presence of a rigid-amorphous phase was evidenced by means of Dynamic Mechanical Thermal Analysis (DMTA) analysis in all the samples under investigation. Lastly, the biodegradation rate of P(PCExNCEy) copolymers was found to slightly increase with the increasing of NCE molar content.

Responsive single-chain polymer nanoparticles with host–guest features

We report a facile approach to form ultra-fine single-chain polymer nanoparticles (SCPNs)viadisulfide-based intrachain crosslinking of single polymer chains of a random copolymer poly(HEMA-co-PDSEMA).

Rapid analysis of water- and fat-soluble vitamins by electrokinetic chromatography with polymeric micelle as pseudostationary phase

A novel polymeric micelle, formed by random copolymer poly (stearyl methacrylate-co-methacrylic acid) (P(SMA-co-MAA)) has been used as pseudostationary phase (PSP) in electrokinetic chromatography (EKC) for simultaneous and rapid determination of 11 kinds of water- and fat-soluble vitamins in this work. The running buffer consisting of 1% (w/v) P(SMA-co-MAA), 10% (v/v) 1-butanol, 20% (v/v) acetonitrile, and 30mM Palitzsch buffer solution (pH 9.2) was applied to improve the selectivity and efficiency, as well as to shorten analysis time. 1-Butanol and acetonitrile as the organic solvent modifiers played the most important roles for rapid separation of these vitamins. The effects of organic solvents on microstructure of the polymeric micelle were investigated. The organic solvents swell the polymeric micelle by three folds, lower down the surface charge density and enhance the microenviromental polarity of the polymeric micelle. The 11 kinds of water- and fat-soluble vitamins could be baseline separated within 13min. The method was applied to determine water- and fat-soluble vitamins in commercial vitamin sample; the recoveries were between 93% and 111% with the relative standard derivations (RSDs) less than 5%. The determination results matched the label claim.

Ultra metal ions and pH sensing characteristics of thermoresponsive luminescent electrospun nanofibers prepared from poly(HPBO-co-NIPAAm-co-SA)

Novel multifunctional fluorescent electrospun (ES) nanofibers were prepared from random copolymers of poly{2-{2-hydroxyl-4-[5-(acryloxy)hexyloxy]phenyl}benzoxazole}-co-(N-isopropylacrylamide)-co-(stearyl acrylate)} (poly(HPBO-co-NIPAAm-co-SA)) using free-radical polymerization, followed by electrospinning. The moieties of HPBO, NIPAAm, and SA were designed to exhibit zinc ion (Zn2+) and pH sensing, thermoresponsiveness, and physical cross-linking, respectively. The ES nanofibers prepared from the P4 copolymer (1 : 93 : 6 composition ratio for HPBO/NIPAAm/SA), showed ultrasensitivity to Zn2+ (as low as 10−8 M) because of the large blue-shifting of 75 nm of the emission maximum and the 2.5-fold enhancement of the emission intensity. Furthermore, the nanofibers exhibited a substantial volume (or hydrophilic–hydrophobic) change during the heating and cooling cycle between 10 °C and 40 °C, attributed to the low critical solution temperature of the thermoresponsive NIPAAm moiety. Such temperature-dependent variation of the prepared nanofibers under the presence of Zn2+ or basic conditions led to a distinct on-off switching of photoluminescence. The high surface-to-volume ratio of the prepared ES nanofibers significantly enhanced their sensitivity compared to that of thin films. These results indicated that the prepared multifunctional ES nanofibers could be potentially used in metal ion, pH, and temperature sensing devices.

Disaggregation and Anionic Activation of Nanodiamonds Mediated by Sodium Hydride—A New Route to Functional Aliphatic Polyester‐Based Nanodiamond Materials

The treatment of bone defects is facing the situation of lacking donations for autotransplantation. As a valid approach, scaffold-based tissue engineering combines the construction of well-defined porous scaffolds with advanced cell culturing technology to guide tissue regeneration. The role for the scaffold is to provide a suitable environment with a sufficient mechanical stiffness, supports for cell attachment, migration, nutrients and metabolite transport and space for cell remodeling and tissue regeneration. The random copolymers poly(L-lactide-co-ɛ-caprolactone) (poly(LLA-co-CL)) and poly(L-lactide-co-1,5-dioxepan-2-one) (poly(LLA-co-DXO)) have been successfully incorporated into 3D porous scaffolds to induce specific interactions with cells and direct osteogenic cell differentiation. In this thesis, these scaffolds have been modified in chemical and physical ways to map and understand requirements for bone regeneration. Scaffold functionalities and properties, such as hydrophilicity, stiffness, size/shape, and reproducibility, were studied. The hydrophilicity was varied by adding 3–20 % (w/w) Tween 80 to poly(LLA-co-CL) and poly(LLA-co-DXO) respectively, which resulted in contact angles from 35° to 15°. With 3 % Tween 80, the resultant mechanical and thermal properties were similar to pristine polymer materials. Tween 80 did not significantly influence cell attachment or proliferation but did stimulate the mRNA expression of osteogenetic markers. The surface functionality and mechanical properties were altered by introducing nanodiamond particles (n-DP) into poly(LLA-co-CL) scaffolds by means of surface physisorption or hybrid blending. Scaffold with n-DP physisorbed showed improved cell attachment, differentiation, and bone reformation. Hybrid n-DP/poly(LLA-co-CL) composites were obtained by direct blending of polylactide modified n-DP (n-DP-PLA) with poly(LLA-coCL). The n-DP-PLA was prepared by sodium hydride-mediated anionic polymerization using n-DP as the initiator. Prepared n-DP-PLA could be dispersed homogenously in organic solvents and blended with poly(LLA-coCL) solution. The n-DP-PLA particles were homogenously distributed in the composite material, which significantly improved mechanical properties. For comparison, the addition of benzoquinone-modified n-DP (n-DP-BQ) did not reinforce poly(LLA-co-CL). This indicated the importance of specific surface grafting, which determined different particle-polymer interactions. For the treatment of critical size defects, a large porous poly(LLA-co-CL) scaffold (12.5 mm diameter × 25 mm thickness) was developed and produced by molding and salt-leaching methods. The large porous scaffolds were evaluated in a scaffold-customized perfusion-based bioreactor system. It was obvious that the scaffold could support improved cell distribution and support the stimulation of human mesenchymal stem cell (hMSC) especially with dynamic flow in a bioreactor. To improve the scaffolding technique, a three-dimensional fiber deposition (3DF) technique was employed to build layer-based scaffolds. Poly(LLA-coCL) scaffolds produced by the 3DF method showed enhanced mechanical properties and a homogeneous distribution of human osteoblasts (hOBs) in the scaffolds. Although poly(LLA-co-CL) was thermally degraded, the degradation did not influence the scaffold mechanical properties. Based on the computerized design, a 3DF scaffold of amorphous copolymer poly(LLAco-CL) provides high-precision control and reproducibility. In summary, the design of porous scaffolds is one of the essential factors in tissue engineering as to mimicking the intrinsic extracellular environment. For bone tissue engineering, an optimized scaffold can maintain a contact angle greater than 35 degrees. Pristine or modified n-DP, introduced as an additive by surface physisorption or direct blending, can improve scaffold mechanical properties and cell response. Various sizes of scaffolds can be easily produced by a mold-mediated salt-leaching method. However, when 100 % reproducibility is required, the 3DF method can be used to create customizable scaffolds.

Degradation reactions during sulphonation of poly(styrene-co-acrylic acid) used as membranes

In this study, a random copolymer of poly(styrene-co-acrylic acid) (PS-AA) was synthesized in solution by radical polymerization and partially crosslinked with divinyl benzene to improve mechanical resistance. The copolymer (PS-AA) was sulphonated with different theoretical molar quantities (20–60%) of sulphuric acid (H2SO4) and acetyl sulphate (CH3COOSO3H). The sulphonated PS-AA materials were characterized with infrared spectroscopy (FTIR), insoluble material percentage by soxhlet extraction, molar mass by gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). FTIR indicated the presence of sulphonic groups bound into the copolymer matrix and some changes in specific bands. Gel percentage was considerably increased when H2SO4 was used as the sulphonation agent while a drop in molecular weight was detected by GPC with acetyl sulphate as the agent. The former effect is due to linkages through the sulphone groups and the latter as a consequence of a polymer matrix destructive side reaction. DSC thermograms show that sulphonation with H2SO4 decreases the Tg value, while CH3COOSO3H increases the transition, in comparison with the neat PS-AA. The latter could be due to the presence of ionic interactions in the copolymer. Side reactions during sulphonation of polymers are very important for the final physical properties.

Thermal properties and crystallization behavior of fractionated blocky and random polyhydroxyalkanoate copolymers from mixed microbial cultures

ABSTRACTThis study represents the first detailed analysis of the thermal, morphological, and crystallization properties of the blend components within a range of mixed‐culture polyhydroxyalkanoates (PHAs), with 3‐hydroxyvalerate content in the as‐produced materials and in the fractions ranging from low (12 mol %) to high (91 mol %). Both coarse and fine fractionation of the as‐produced copolymers confirmed that they were blends of nominally blocky and/or random copolymers of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate), with very broad compositional distributions as governed by the PHA accumulation strategy. The crystallization kinetics and thermal properties of the fractions were found to be very significantly different from each other, consistent with the hypothesis that the overall mechanical properties were primarily controlled by the more rapidly crystallizing components. Two materials produced using an alternating feeding strategy demonstrated unique crystallization and thermal properties in their fractions, which are considered to have contributed to distinctly more elastic mechanical properties in these particular samples. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40836.

Biodegradable aliphatic copolyesters containing PEG-like sequences for sustainable food packaging applications

Abstract A series of novel random copolymers of poly(butylene 1,4-cyclohexanedicarboxylate) (PBCE) containing triethylene glycol sub-unit (P(BCEmTECEn)) were synthesized and characterized in terms of molecular and solid-state properties, among these barrier properties to different gases (oxygen and carbon dioxide). In addition, biodegradability studies both in soil and in compost and ecotoxicological analysis, by means of the Lepidium sativum test, have been conducted. The copolymers displayed a high and similar thermal stability with respect to PBCE. At room temperature, all the copolymers appeared as semicrystalline materials: the main effect of copolymerization was a lowering of crystallinity degree (χc) and a decrease of the melting temperature compared to the parent homopolymer. The Baur's equation well described the Tm-composition data. Final properties and biodegradation rate of the materials under study were strictly dependent on copolymer composition and χc. As a matter of fact, hydrophilicity regularly increased with the increasing of TECE mol%, due to the PEG-like portion. The elastic modulus and the elongation to break decreased and increased, respectively, as TECE unit content was increased. As to the barrier properties, the selectivity ratios for the examined samples increased with the increasing of TECE mol%, confirming the correlation between the permeability and the chemical composition. The copolymers with lower TECE unit content (up to 30 mol%) showed improved barrier properties with respect to polylactide films tested under the same conditions. Lastly, the biodegradation rate of P(BCEmTECEn) copolymers increased with the increasing of TECE mol%, while PBCE remained almost undegraded in the explored conditions.

Detection of Dissolved CO2 Based on the Aggregation of Gold Nanoparticles

A sensitive colorimetric assay of dissolved CO2 (dCO2) was developed based on the plasmon shift of gold nanoparticles (AuNPs). A water-soluble random copolymer poly(dimethyl acrylamide-co-(N-amidino)ethyl acrylamide), or P(DMA-co-NAEAA), containing amidine groups was synthesized. In the presence of dCO2, the amidine groups in the NAEAA block protonate and convert the polymer from a neutral to a positive-charged state, hence triggering the negative-charged AuNPs to aggregate by the electrostatic interaction. The degree of AuNP aggregation is dependent on the charge density of polymer, which is related to dCO2 concentration. The aggregation of AuNPs results in a red shift of the AuNP plasmonic spectrum, or a color change from red to blue. In addition, dCO2 concentration can be quantitatively measured by the UV absorbance change of the AuNP solution. A linear relationship between 0.264 and 6.336 hPa of dCO2 with a limit of detection (LOD) of 0.04 hPa can be acquired. This is the first report to detect dCO2 using the optical properties of nanoparticles.

Amphiphilic polymeric micelle as pseudostationary phase in electrokinetic chromatography for analysis of eight corticosteroids in cosmetics

Amphiphilic polymeric micelle, as a novel pseudostationary phase in EKC was used to determine eight kinds of corticosteroids namely hydrocortisone, prednisolone, hydrocortisone acetate, prednisone, cortisone acetate, prednisolone acetate, dexamethasone, and triamcinolone acetonide in cosmetics. Amphiphilic random copolymer poly(methyl methacrylate-co-methacrylic acid) (P(MMA-co-MAA)) was micellizated via neutralization in alkaline aqueous solution. The influences of the molar ratio of monomer MMA to MAA, the concentration of polymer and pH on the polymeric micelle microstructure and EKC performances were investigated. As molar ratio of MMA to MAA in P(MMA-co-MAA) increased, both CMC and environmental polarity of the inner core in polymeric micelle decreased dramatically. With increasing monomer ratio, the size of polymeric micelles increased firstly, and then decreased, finally increased again. ζ potential of the micelle had a slight decline trend. As increment of polymer concentration, the size of the polymeric micelle increased steadily. By optimizing the monomer ratio, the polymer concentration, and pH of the running buffer, as well as operation conditions such as separation voltage and temperature, the eight analytes could be separated within 16.5 min using 7.5 mg/mL polymer with the monomer ratio of 7:3 dissolved in pH 9.2 borax buffer as the running buffer. The method has been used for analysis of corticosteroids in cosmetic samples with simple extraction; the recoveries for eight analytes were between 85.9 and 106%. This method was of accuracy, repeatability, pretreatment simplicity, and could be applied to the quality control of cosmetics.