Poly‐3‐hydroxyalkanoates‐co‐polyethylene glycol methacrylate copolymers for pH responsive and shape memory hydrogel

Multifunctional hydrogels combining the capabilities of cellular pH responsiveness and shape memory, are highly promising for the realization of smart membrane filters, controlled drug released devices, and functional tissue‐engineering scaffolds. In this study, lipase was used to catalyze the synthesis of medium‐chain‐length poly‐3‐hydroxyalkanoates‐co‐polyethylene glycol methacrylate (PHA‐PEGMA) macromer, which was used to prepare pH‐responsive and shape memory hydrogel via free radical polymerization. Increasing the PEGMA fraction from 10 to 50% (mass) resulted in increased thermal degradation temperature (T_d) from 430 to 470°C. Highest lower critical solution temperature of 37°C was obtained in hydrogel with 50% PEGMA fraction. The change in PEGMA fraction was also found to highly influence the hydrogel's hydration rate (r) from 2.8 × 10^?5 to 7.6 × 10^?5 mL·s^?1. The hydrogel's equilibrium weight swelling ratio (q_e), protein release and its diffusion coefficient (D_m) were all found to be pH dependent. Increasing the phosphate buffer pH from 2.4 to 13 resulted in increased q_e from 2 to 16 corresponding to the enlarging of network pore size (ξ) from 150 to 586 nm. Different types of crosslinker for the hydrogel influenced its flexibility and ductility. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41149.     

A modified quasi‐creep model for assessment of deformation of topas COC substrates in the thermal bonding of microfluidic devices: Experiments and modeling

The effects of thermomechanical properties of dissimilar polymer plates on thermal bonding were investigated and the resultant deformation of cover Topas COC plate was modeled using a simplified quasi‐creep model. The appropriate conditions for thermal bonding for minimal deformation of both the Topas cover and substrate plates could be established through simulation using the quasi‐creep model. Both the cover plate and the substrate containing microchannels were fabricated by injection molding. The elastic modulus of the COC plate at different temperatures was measured using three‐point bending test. The thermal bonding was conducted at different temperatures, pressures, and holding times. The deformation of the cover plate (consisting of Topas with a lower glass transition temperature, T_g) into the microchannel of the substrate plate (consisting of Topas with a higher T_g) was found to be significant even at lower bonding pressures when the bonding temperature was higher than a critical temperature. Such deformation was dependent on the viscoelastic creep behavior of the material and the thermal bonding temperature and load. This deformation behavior was predicted by the numerical model, and the predicted results agree well with the experimental data. The bonding strength of the sealed microchannels was evaluated using the burst test. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

An analytical solution to the extended Navier–Stokes equations using the Lambert W function

Microchannel gas flows are of importance in a wide range of microelectro mechanical devices. In these flows, the mean free path of the gas can be comparable to the characteristic length of the microchannel, leading to strong diffusion‐enhanced transport of momentum. Numerical solutions to the extended Navier–Stokes equations (ENSE) have successfully modeled such microchannel flows. Analytical solutions to the ENSE for the pressure and velocity fields using the Lambert W function are derived. We find that diffusive contributions to the total transport are only dominant for low average pressures and low pressure drops across the microchannel. For large inlet pressures, we show that the expressions involving the Lambert W function predict steep gradients in the pressure and velocity localized near the channel exit. We extract a characteristic length for this boundary layer. Our analytical results are validated by numerical and experimental results available in the literature. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1413–1423, 2014     

Preparation of narrow‐disperse or monodisperse poly{[poly(ethylene glycol) methyl ether acrylate]‐co‐(acrylic acid)} microspheres with ethyleneglycol dimethacrylate as crosslinker by distillation precipitation polymerization

Narrow‐disperse or monodisperse poly{[poly(ethylene glycol) methyl ether acrylate]‐co‐(acrylic acid)} (poly(PEGMA‐co‐AA)) microspheres were prepared by distillation precipitation polymerization with ethyleneglycol dimethacrylate (EGDMA) as crosslinker with 2,2′‐azobisisobutyronitrile as initiator in neat acetonitrile in the absence of any stabilizer, without stirring. The diameters of the resultant poly(PEGMA‐co‐AA‐co‐EGDMA) microspheres were in the range 200–700 nm with a polydispersity index of 1.01–1.14, which depended on the comonomer feed of the polymerization. The addition of the hydrogen bonding monomer acrylic acid played an essential role in the formation of narrow‐disperse or monodisperse polymer microspheres during the polymerization. Copyright © 2006 Society of Chemical Industry     

The effect of system pressure on gas‐liquid slug flow in a microchannel

Characteristics of gas‐liquid two‐phase flow under elevated pressures up to 3.0 MPa in a microchannel are investigated to provide the guidance for microreactor designs relevant to industrial application. The results indicate that a strong leakage flow through the channel corners occurs although the gas bubbles block the channel. With a simplified estimation, the leakage flow is shown to increase with an increase in pressure, leading to a bubble formation shifting from transition regime to squeezing regime. During the formation process, the two‐phase dynamic interaction at the T‐junction entrance would have a significant influence on the flow in the main channel as the moving velocity of generated bubbles varies periodically with the formation cycle. Other characteristics such as bubble formation frequency, bubble and slug lengths, bubble velocities, gas hold‐up, and the specific surface area are also discussed under different system pressures. © 2013 American Institute of Chemical Engineers AIChE J, 60: 1132–1142, 2014     

Superabsorbent polymeric materials. XI. Effect of nonionic monomers on the swelling behavior of crosslinked poly(sodium acrylate‐co‐nonionic monomers) in aqueous salt solutions

A series of xerogels based on sodium acrylate, nonionic monomers such as 2‐hydroxyethyl methacrylate (HEMA) and poly(ethylene glycol) methacrylate (PEGMA), and N,N′‐methylene bisacrylamide were prepared by inverse suspension polymerization. The results indicate that the water absorbencies for these two gel series were effectively improved by the addition of a small amount of nonionic monomer (HEMA or PEGMA). The initial absorption rates in deionized water were faster for the PEGMA gels than for the HEMA gels. Scanning electron microscopy showed that the spherical particle size was smaller for the PEGMA gels than for the HEMA gels. In addition, the water absorbency of the gels in various salt solutions decreased with increasing ionic strength, especially for the multivalent salt solutions. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3666–3674, 2004     

Amphiphilic poly(vinyl chloride)‐g‐poly[poly(ethylene glycol) methylether methacrylate] copolymer for the surface hydrophilicity modification of poly(vinylidene fluoride) membrane

In this study, a comblike amphiphilic graft copolymer containing poly(vinyl chloride) (PVC) backbones and poly(oxyethylene methacrylate) [poly(ethylene glycol) methylether methacrylate (PEGMA)] side chains was facilely synthesized via an atom transfer radical polymerization method. Secondary chlorines in PVC were used as initial sites to graft a poly[poly(ethylene glycol) methylether methacrylate] [P(PEGMA)] brush. The synthesized PVC‐g‐P(PEGMA) graft copolymer served as an efficient additive for the hydrophilicity modification of the poly(vinylidene fluoride) (PVDF) membrane via a nonsolvent‐induced phase‐inversion technique. A larger pore size, higher porosity, and better connectivity were obtained for the modified PVDF membrane; this facilitated the permeability compared to the corresponding virgin PVDF membrane. In addition, the modified PVDF membrane showed a distinctively enhanced hydrophilicity and antifouling resistance, as suggested by the contact angle measurement and flux of bovine serum albumin solution tests, respectively. Accordingly, the PVC‐g‐P(PEGMA) graft copolymer was demonstrated as a successful additive for the hydrophilicity modification, and this study will likely open up new possibilities for the development of efficient amphiphilic PVC‐based copolymers for the excellent hydrophilicity modification of PVDF membranes. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Velocity Distribution inside a Laminated‐Sheet Microchannel Reactor

In a laminated‐sheet microchannel reactor, several microchannel sheets with the same or different structures are mutually laminated together. The effect of microchannel and manifold structure as well as the number of laminated sheets on the velocity distribution among microchannels in each sheet with the same structure is investigated. Results indicate that a large microchannel length, a high‐aspect‐ratio microchannel, and centrosymmetric manifold structure are favorable for a relatively uniform velocity distribution in each sheet. Considering the centrosymmetric manifold structure, a shorter distance from inlet and outlet to microchannels in direction of the microchannel width and a longer distance to the microchannel array in direction of the microchannel length can contribute to a more uniform velocity distribution. The laminated‐sheet number has only a minor impact on the velocity distribution among microchannels in each sheet.     

Synthesis of stimuli‐responsive star‐like copolymer H20‐PNIPAm‐r‐PEGMA via the ATRP copolymerization technique and its micellization in aqueous solution

A series of novel star‐like copolymers H20‐poly(N‐isopropylacrylamide)‐random‐poly(poly(ethylene glycol) methyl ether methacrylate) (H20‐PNIPAm‐r‐PEGMA), which could respond to both temperature and ionic strength stimuli in aqueous solution were synthesized by atom transfer radical polymerization. Stimuli‐response of these copolymers in aqueous solution was characterized by dynamic laser scattering (DLS), ¹H‐NMR and turbidity. In aqueous solution, these star‐like copolymers exhibited response to temperature and ionic strength with tunable low‐critical solution temperature (LCST) from 32 to 100°C. The LCST values of copolymers increased with increasing PEGMA contents, while decreased with increasing ionic strength. An interesting phenomenon, which should be a unique character of star‐like copolymer, was observed by the turbidity test of copolymer 1160. The addition of sodium chloride and increase of concentration can let copolymer 1160 behave normally, which was further confirmed by atomic force microscopy and DLS. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and investigation of a new macroporous monolithic material based on an N‐hydroxyphthalimide ester of acrylic acid‐co‐glycidyl methacrylate‐co‐ethylene dimethacrylate terpolymer

A macroporous monolithic material based on an N‐hydroxyphthalimide ester of acrylic acid‐co‐glycidyl methacrylate‐co‐ethylene dimethacrylate terpolymer was synthesized by photoinitiated free‐radical polymerization. Several porogenic solvents, such as cyclohexanol, dodecanol, and poly(ethylene glycol)s, were tested to obtain the monolithic material with an optimal pore size allowing unrestricted penetration of large molecule (proteins) into a three‐dimensional porous space. The new monolithic material was covalently bound to an inert surface (glass) directly in the polymerization step, and it was suggested as a solid matrix for the development of new types of three‐dimensional protein microarrays (biochips). A demonstration of the potential of the suggested microarray platform as well as optimization of microarray performance conditions was realized with a model mouse immunoglobulin G/goat anti‐mouse immunoglobulin G affinity pair. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

High‐throughput microporous tube‐in‐tube microreactor as novel gas–liquid contactor: Mass transfer study

High‐throughput microporous tube‐in‐tube microchannel reactor (MTMCR) was first designed and developed as a novel gas–liquid contactor. Experimentally measured k_Lα in MTMCR is at least one or two orders of magnitude higher than those in the conventional gas–liquid contactors. A high throughput of 500 L/h for gas and 43.31 L/h for liquid is over 60 times higher than that of T‐type microchannel. An increase of the gas or liquid flow rate, as well as a reduction of the micropore size and annular channel width of MTMCR, could greatly intensify the gas–liquid mass transfer. The interfacial area, α, in MTMCR was measured to be as high as 2.2 × 10⁵ m²/m³, which is much higher than those of microchannels (3400–9000 m²/m³) and traditional contactors (50–2050 m²/m³). The artificial neural network model was proposed for predicting α, revealing only an average absolute relative error of <5%. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Stabilization of CO2‐in‐water emulsions with high internal phase volume using PVAc‐b‐PVP and PVP‐b‐PVAc‐b‐PVP as emulsifying agents

Two newly‐designed hydrocarbon surfactants, that is, poly(vinyl acetate)‐block‐poly(1‐vinyl‐2‐pyrrolidone) (PVAc‐b‐PVP) and PVP‐b‐PVAc‐b‐PVP, were synthesized using reversible addition–fragmentation chain transfer polymerization and used to form CO₂/water (C/W) emulsions with high internal phase volume and good stability against flocculation and coalescence up to 60 h. Their structures were precisely determined by nuclear magnetic resonance, gel permeation chromatography, thermal gravimetric analysis, and differential scanning calorimetry. Besides low temperature and high CO₂ pressure, the surfactant structures were the key factors affecting the formation and stability of high internal phase C/W emulsions, including the polymerization degrees of CO₂‐philic block (PVAc) and hydrophilic block (PVP), as well as the number of hydrophilic tail. The surface tension of the surfactant aqueous solution and the apparent viscosity of the C/W emulsions were also measured to characterize the surfactants efficiency and effectiveness. The surfactants with double hydrophilic tails showed stronger emulsifying ability than those with single hydrophilic tail. The great enhancement of the emulsions stability was due to decrease of the interface tension as well as increase of the steric hindrance in the water lamellae, preventing a frequent collision of CO₂ droplets and their fast coalescence. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46351.     

Determination of trace macrolide antibiotics in milk with online solid‐phase extraction with an ionic‐liquid‐based monolithic column

An ionic liquid (IL)‐based monolithic poly(ionic liquid glycidylmethacrylate‐co‐ethylene glycol dimethacrylate) column was prepared via in situ free‐radical polymerization with 1‐vinyl‐3‐butylimidazolium chlorine as one of the comonomers. The obtained monolithic column was used as the sorbent of solid‐phase extraction (SPE) and coupled with high‐performance liquid chromatography for the simultaneous determination of the macrolide antibiotics roxithromycin (ROX) and acetylspiramycin (ACE) in processed pure milk. The monolithic column was characterized by Fourier transform infrared spectrometry, scanning electron microscopy, nitrogen absorption–desorption, mercury intrusion porosimetry, and thermogravimetric analysis. The results reveal that the monolithic column exhibited a high selectivity and good permeability to the macrolide antibiotics in milk. The optimized method offered excellent linearity with a linear regression coefficient greater than 0.998. The precisions for interday and intraday were both less than 7.7%. The accuracies expressed by the recoveries for ROX and ACE were in the ranges 92.5–103.8 and 93.0–107.6%, respectively. Compared to the previous methods, this method had a low limit of detection and a good accuracy. As a result, the polymer IL based monolithic column could feasibly be used as a high‐selectivity online SPE sorbent for determining trace macrolide antibiotics in milk. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43943.     

Determination of cake properties in ultrafiltration of nano‐colloids based on single step‐up pressure filtration test

The single step‐up pressure filtration test was developed to determine the pressure dependence of average specific resistance of the cake formed in ultrafiltration of a variety of nano‐colloids over a wide range of pressure drops across the cake. The values of the average specific resistance at extremely low pressures were obtained from only the flux decline data through the use of the distinct time variation of the pressure drop across the cake generated by using the ultrafiltration membrane with a high hydraulic resistance under the low filtration pressure in the first step of filtration. The values at higher pressures were obtained from the time variation of the filtration rate induced by a stepwise increase in the pressure. The correlations between the average specific cake resistance and the pressure drop across the cake were evaluated using only the flux decline data for a variety of different proteins and nanoparticles. © 2013 American Institute of Chemical Engineers AIChE J, 60: 289–299, 2014     

Effect of acrylic copolymer dispersants bearing epoxy groups on rheological and dielectric properties of carbon black‐filled epoxy system

In this article, the use of copolymeric dispersants with an acrylic backbone and epoxy side groups for formulating carbon black (CB)‐epoxy composites are described. Six epoxy‐containing acrylic copolymer dispersants were prepared from hexyl methacrylate (HMA), poly(ethylene glycol) ethyl ether methacrylate (PEGMA), and glycidyl methacrylate via a group transfer polymerization technique. The epoxy‐containing acrylic copolymer of the highest concentration of PEGMA showed a desirable passivation effect on CB, and was found to lower the viscosity of the CB‐epoxy paste, leading to the well‐cured composite after heat treatment. The thick composite film prepared by employing the [CB/acrylic dispersant/epoxy] paste was built up on a Cu plate by a screen printing process followed by thermal curing. The dielectric properties of the 3.1 vol % CB‐filled epoxy film showed us high dielectric constant (Dk 4900) and rather low dissipation factor (Df 29%) at 1 MHz. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Poly(ethylene glycol) methyl ether methacrylate‐graft‐chitosan nanoparticles as a biobased nanofiller for a poly(lactic acid) blend: Radiation‐induced grafting and performance studies

In this study, we aimed to modify chitosan (CS) as a novel compatible bio‐based nanofiller for improving the compatibility including the thermal and mechanical properties of poly(lactic acid) (PLA). The modification of CS with poly(ethylene glycol) methyl ether methacrylate (PEGMA) was done by radiation‐induced graft copolymerization. The effects of the dose rate, irradiation dose, and PEGMA concentration on the degree of grating (DG) were investigated. The chemical structure, packing structure, thermal stability, particle morphology, and size of the PEGMA‐graft‐chitosan nanoparticles (PEGMA‐graft‐CSNPs) were characterized by fourier transform infrared spectroscopy, X‐ray diffraction, thermogravimetric analysis, and transmission electron microscopy. The compatibility of the PEGMA‐graft‐CSNP/PLA blends was also assessed by field emission scanning electron microscopy. The PEGMA‐graft‐CSNPs exhibited a spherical shape with the DG and particle sizes in the ranges of 3–145% and 35–104 nm, respectively. The PEGMA‐graft‐CSNPs showed compatible with PLA because of the grafted PEGMA segment. A model case study of the PEGMA‐graft‐CSNP/PLA blend demonstrated the improvement not only the compatibility but also thermal stability flexibility, and ductility of PLA. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42522.     

Oil–water two‐phase flow in microchannels: Flow patterns and pressure drop measurements

This paper investigates oil–water two‐phase flows in microchannels of 793 and 667 µm hydraulic diameters made of quartz and glass, respectively. By injecting one fluid at a constant flow rate and the second at variable flow rate, different flow patterns were identified and mapped and the corresponding two‐phase pressure drops were measured. Measurements of the pressure drops were interpreted using the homogeneous and Lockhart–Martinelli models developed for two‐phase flows in pipes. The results show similarity to both liquid–liquid flow in pipes and to gas–liquid flow in microchannels. We find a strong dependence of pressure drop on flow rates, microchannel material, and the first fluid injected into the microchannel.     

Viscoelastic and adhesive properties of single‐component thermo‐resistant acrylic pressure sensitive adhesives

Poly(butyl acrylate‐vinyl acetate‐acrylic acid) based acrylic pressure sensitive adhesives (PSAs) were synthesized by solution polymerization for the fabrication of high performance pressure sensitive adhesive tapes. The synthesized PSAs have high shear strength and can be peeled off substrate without residues on the substrate at temperature up to 150°C. The PSAs synthesized in the present work are single‐component crosslinked and they can be used directly once synthesized, which is convenient for real applications compared to commercial multi‐component adhesives. The results demonstrated that the viscosity of the PSAs remained stable during prolonged storage. The effects of the preparation conditions such as initiator concentration, cross‐linker amount, organosiloxane monomer amount and tackifier resin on the polymer properties, such as glass transition temperature (T_g), molecular weight (M_w), surface energy and shear modulus, were studied, and the dependence of the adhesive properties on the polymer properties were also investigated. Crosslinking reactions showed a great improvement in the shear strength at high temperature. The addition of tackifier resin made peel strength increase compared to original PSAs because of the improvement of the adhesion strength. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40086.     

Biodegradable polymersomes from four‐arm PEG‐b‐PDLLA for encapsulating hemoglobin

A series of four‐arm star block copolymers poly(ethylene glycol)‐block‐poly(d,l ‐lactide) (PEG‐PDLLA) with different hydrophobic length were synthesized by ring‐opening polymerization of lactide and characterized using ¹H NMR and gel permeation chromatography (GPC). These copolymers could self‐assemble in aqueous solution to form the vesicle structure with controlled size and morphologies. Transmission electron microscopy (TEM) and DLS show the polymersomes are spherical with diameter of 70～500 nm. The polymersomes made by direct hydration of copolymer thin films in water exhibit the controllable ability of encapsulating hemoglobin under mild condition. The hemoglobin content in the polymersomes could reach to 35 wt %. More importantly, the encapsulated hemoglobin keeps its own bioactivity and is capable of binding oxygen. This hemoglobin‐encapsulated four‐arm PEG‐PLA polymersomes could have the potential to be applied as an artificial oxygen carrier for transfusion. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40433.     

Preparation and flocculation behavior of cellulose‐g‐PMOTAC copolymer

As a contribution to the wider use of biodegradable materials, this article reports the synthesis and testing of cationic polyelectrolyte cellulose derivatives for use as flocculation chemicals. Cellulose macroinitiator is synthesized in DMAc/LiCl solvent system by direct acylation of cellulose with 2‐bromoisobutyryl bromide. Cellulose‐graft‐poly(N,N‐dimethyl aminoethyl methacrylate) (cellulose‐g‐PDMAEMA) copolymers are prepared by copper‐mediated radical polymerization in homogeneous medium. Formation of the macroinitiator and graft copolymers is confirmed by ATR‐FTIR and ¹H NMR. Quaternization of the graft chains to poly(methacryloxyethyl trimethylammonium chloride) (PMOTAC) produces cellulose‐g‐PMOTAC, which performs similarly to a commercial product in flocculation of pulp and kaolin. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40448.