Di(ethylene Glycol) Methyl Ether Methacrylate Research Articles

RAFT copolymerization of methyl methacrylate and di(ethylene glycol) methyl ether methacrylate in a hexylpyridinium ionic liquid

AbstractSmart polymers undergo significant physical or chemical changes in response to stimuli like temperature and pH. Achieving a narrow molecular weight distribution is crucial for their sensitivity. Reversible addition–fragmentation chain transfer (RAFT) in ionic liquids is an effective method for synthesizing such polymers due to its favorable kinetics and environmental benefits. Most studies use imidazolium ionic liquids, while pyridinium ionic liquids are less common despite their easy synthesis. This study reports the first successful RAFT copolymerization of di(ethylene glycol) methyl ether methacrylate (DEGMEMA) and methyl methacrylate in N‐hexylpyridinium hexafluorophosphate ([HPY][PF6]). Both linear and hyperbranched copolymers (Mn > 25,000) with narrow molecular weight distribution were synthesized, showing observable temperature responses and biocompatibility. The linear copolymers had a desirable dispersity (Ð) of less than 1.10, while the hyperbranched copolymer had a Ð of 2.034. The lower critical solution temperatures (LCSTs) of the copolymers were close to or below the LCST of PDEGMEMA (26°C). This study indicates that pyridinium ionic liquids can be explored as a suitable solvent for synthesizing methacrylate‐based smart polymers.

Investigating oligo(ethylene glycol) methacrylate thermoresponsive copolymers

Methacrylate-based polymers are frequently used in the development of thermoresponsive smart materials for biomedical applications. Among all the routes to such polymers, reversible addition fragmentation chain transfer (RAFT) copolymerisation is one of the most widely used. This paper reports the synthesis of thermoresponsive copolymers comprising oligo(ethylene glycol) methyl ether methacrylate with Mn of 300 (OEGMA300) and di(ethylene glycol) methyl ether methacrylate (DiEGMA). Polymers of molecular weight up to 100 kDA were obtained via RAFT polymerisation, mediated by a dithiobenzoate chain transfer agent (CTA) at 70 °C. An appropriate solvent, ratio of initiator to monomers, and minimum reaction polymerisation time were essential to provide optimum polymers. The synthesis of homogenous p(OEGMA300-co-DIEGMA) polymers with PDI of 1.1–1.2 was achieved in toluene with ≥10 h of reaction. Increasing the molecular weight of the p(OEGMA300-co-DiEGMA) polymers decreases the polydispersity index. p(OEGMA300-co-DiEGMA) polymers with Mw of 50,000 Da were successfully synthesised with lower critical solution temperatures (LCSTs) of 41.3 °C, 43.0 °C and >45 °C for OEGMA300:DiEGMA molar ratios of 2:8, 3:7 and 4:6, respectively. Further, the LCST was not found to be affected by the polymer molecular weight. The p(OEGMA300-co-DiEGMA) polymers showed no cytotoxicity to Caco-2 cells at a concentration of 1 mg mL−1, whereas a decrease of HDF cell viability by up to 26.5 % was seen. These polymers could be beneficial for several biomedical applications, such as developing formulations for temperature-triggered drug delivery.

ABC block copolymer micelles driving the thermogelation: Scattering, imaging and spectroscopy

Thermoresponsive polymers have attracted much scientific attention due to their capacity for temperature-driven hydrogel formation. For biomedical applications, such as drug delivery, this transition should be tuned below body temperature to facilitate controlled and targeted drug release. We have recently developed a thermoresponsive polymer that forms gel at low concentrations (2 w/w%) in aqueous media and offers a cost-effective alternative to thermoresponsive systems currently being applied in clinics. This polymer is an ABC triblock terpolymer, where A, B, and C correspond to oligo(ethylene glycol) methyl ether methacrylate with average Mn 300 g mol−1 (OEGMA300), n-butyl methacrylate (BuMA), and di(ethylene glycol) methyl ether methacrylate (DEGMA). To investigate the self-assembly and the gelation mechanism in diluted solutions, we used small-angle neutron scattering (SANS) on 1 w/w% (below the gelation concentration) and 5 w/w% solutions (above the gelation concentration). As a comparison, we also investigated the solutions of the most studied thermoresponsive polymer, namely, Pluronic F127, an ABA triblock bipolymer made of ethylene glycol (A) and propylene glycol (B) blocks. SANS revealed that the in-house synthesised polymer forms elliptical cylinders, whose length increases significantly with temperature. In contrast, Pluronic F127 solutions form core-shell spherical micelles, which slightly elongate with temperature. Transmission electron microscopy images support the SANS findings, with tubular/worm structures being present. Variable-temperature circular dichroism (CD) and proton nuclear magnetic resonance (1H NMR) spectroscopy experiments reveal insights on the tacticity, structural changes, and molecular origin of the self-assembly.

Block sequence dependent self-assembly and optoelectronic behavior of thermo- and pH-sensitive Polythiophene-graft-[Poly(diethylene glycol methyl ether methacrylate)-block-Poly(dimethyl amino ethyl methacrylate)] copolymers

To overcome the difficulty of using multistep process we report an one pot synthesis of polythiophene (PT)-graft block copolymers with thermo-sensitive poly(diethyleneglycol methyl ether methacrylate)(PDEGMEM) and pH-sensitive poly(dimethyl amino ethyl methacrylate)(PDMAEMA) using ATRP technique. The polymers PT-g-(PDEGMEM10-b-PDMAEMA3) (P1), PT-g-(PDMAEMA10-b-PDEGMEM3) (P2) and PT-g-(PDMAEMA6-ran-PDEGMEM8) (P3) are characterized by 1H NMR and SEC techniques. HRTEM study shows that P1 and P3 exhibit micellar morphology but P2 shows vesicular morphology, all sizes increase with increasing pH and temperature. UV–vis absorption spectra show pH, temperature and sequence dependent absorbance peak, and dc-conductivity (P2 > P3 > P1) indicates semi-conducting nature. Current-Voltage (I-V) property shows pH dependent memory and OMEIC property following above order. At pH3, on irradiation with white light the photocurrent gains of P2, P3 and P1 are 7.9, 6.6 and 3.5, respectively. Thus PT-graft block copolymers exhibit tunable self-assembly, optoelectronic, transport and photocurrent properties depending on proximity and preponderance of block sequence from PT backbone and also for their pH and thermo-responsivity.

Thermo-responsive poly(di(ethylene glycol) methyl ether methacrylate) brushes as substrate-independent release coatings for cell culture and selective cell separation and purification

Abstract A systematic study on the surface-initiated polymerization of di(ethylene glycol) methyl ether methacrylate (DEGMA) by atom transfer radical polymerization (ATRP) from glass, silicon, titanium as well as tissue culture polystyrene (TCPS) is reported in an attempt to expand the known thermoresponsive poly(di(ethylene glycol) methyl ether methacrylate) (PDEGMA) cell release layers on gold to other substrates. The use of these substrate materials requires an altered immobilization chemistry to couple a bromide containing ATRP initiator to the surfaces. Using aminosilanes or polydopamine as coupling layers for the attachment of α-bromoisobutyryl bromide (BiBB) and the direct functionalization of surface hydroxyl groups with trichlorosilane-functionalized ATRP initiators all surfaces studied were shown to facilitate the growth of PDEGMA brushes using the same conditions that were reported previously for polymerization on gold. The brush layers obtained were characterized systematically using wetting, ellipsometry, X-ray photoelectron spectroscopy (XPS) as well as atomic force microscopy (AFM) analyses. Selective cell release and separation of PaTu 8988t and NIH 3T3 cells, which are known to exhibit different behavior after temperature drop-induced brush swelling, was observed for all substrates, albeit for different brush thicknesses, implying variations in initiator and also PDEGMA grafting density. The successful modification of biomedically relevant materials (Ti and TCPS) implies that the previously reported stem cell purification and selective cell release of various cell types, which is facilitated by PDEGMA brushes, can be realized and consequently scaled up in the future.

Design of multi-responsive and actuating microgels toward on-demand drug release.

Multifunctional colloidal microgels that exhibit stimuli-responsive behaviour and excellent biocompatibility have attracted particular attention for developing functional compartmentalized networks. Herein, a series of stimuli-responsive microgels (M0, M1, and M2) were designed through the copolymerization of di(ethylene glycol) methyl ether methacrylate (DEGMA) and methacrylic acid (MAA) monomers using hydroxy ethyl methacrylate-coupled azobenzene (HEMA-Az) and ethylene glycol dimetharylate (EGDMA) as crosslinkers. The behaviour of the microgels in response to temperature, pH, and light was thoroughly investigated using spectroscopic, microscopic, and light-scattering techniques. Interestingly, the microgels deswelled with an increase in temperature, decrease in pH, and under the irradiation of UV light. Such a reversible swelling/deswelling behaviour was exploited for microgel M2, which showed better photoactuation at pH 5 with a higher fluid pumping velocity. The actuating microgel M2 was optimized for loading the drug ciprofloxacin (Cf) to study its release at different temperature, pH, and light conditions. Microgel M2 exhibited photoresponsive Cf release at pH 5 and 37 °C, demonstrating its potential for application in on-demand drug release.

Synthesis and Self-Assembly of Hyperbranched Multiarm Copolymer Lysozyme Conjugates Based on Light-Induced Metal-Free Atrp

In recent years, the coupling of structurally and functionally controllable polymers with biologically active protein materials to obtain polymer-protein conjugates with excellent overall properties and good biocompatibility has been important research in the field of polymers. In this study, the hyperbranched polymer hP(DEGMA-co-OEGMA) was first prepared by combining self-condensation vinyl polymerization (SCVP) with photo-induced metal-free atom transfer radical polymerization (ATRP), with 2-(2-bromo-2-methylpropanoyloxy) ethyl methacrylate (BMA) as inimer, and Di (ethylene glycol) methyl ether methacrylate (DEGMA) and (oligoethylene glycol) methacrylate (OEGMA, Mn = 300) as the copolymer monomer. Then, hP(DEGMA-co-OEGMA) was used as a macroinitiator to continue the polymerization of a segment of pyridyl disulfide ethyl methacrylate (DSMA) monomer to obtain the hyperbranched multiarm copolymers hP(DEGMA-co-OEGMA)-star-PDSMA. Finally, the lysozyme with sulfhydryl groups was affixed to the hyperbranched multiarm copolymers by the exchange reaction between sulfhydryl groups and disulfide bonds to obtain the copolymer protein conjugates hP(DEGMA-co-OEGMA)-star-PLZ. Three hyperbranched multiarm copolymers with relatively close molecular weights but different degrees of branching were prepared, and all three conjugates could self-assemble to form nanoscale vesicle assemblies with narrow dispersion. The biological activity and secondary structure of lysozyme on the assemblies remained essentially unchanged.

Thermo- and pH-responsive poly[(diethylene glycol methyl ether methacrylate)-co-(2-diisopropylamino ethyl methacrylate)] hyperbranched copolymers: self-assembly and drug-loading

P(DEGMA-co-DIPAEMA) hyperbranched copolymers self-assemble into large polymeric aggregates in aqueous media, when the amino groups of DIPAEMA segments are fully protonated at extreme temperatures (25 °C and 55 °C).

Application of Multi-Layered Temperature-Responsive Polymer Brushes Coating on Titanium Surface to Inhibit Biofilm Associated Infection in Orthopedic Surgery

Infection associated with biomedical implants remains the main cause of failure, leading to reoperation after orthopedic surgery. Orthopedic infections are characterized by microbial biofilm formation on the implant surface, which makes it challenging to diagnose and treat. One potential method to prevent and treat such complications is to deliver a sufficient dose of antibiotics at the onset of infection. This strategy can be realized by coating the implant with thermoregulatory polymers and triggering the release of antibiotics during the acute phase of infection. We developed a multi-layered temperature-responsive polymer brush (MLTRPB) coating that can release antibiotics once the temperature reaches a lower critical solution temperature (LCST). The coating system was developed using copolymers composed of diethylene glycol methyl ether methacrylate and 2-hydroxyethyl methacrylate by alternatively fabricating monomers layer by layer on the titanium surface. LCST was set to the temperature of 38-40 °C, a local temperature that can be reached during infection. The antibiotic elution characteristics were investigated, and the antimicrobial efficacy was tested against S. aureus species (Xen29 ATCC 29 213) using one to four layers of MLTRPB. Both in vitro and in vivo assessments demonstrated preventive effects when more than four layers of the coating were applied, ensuring promising antibacterial effects of the MLTRPB coating.

Novel porphyrin-containing hydrogels obtained by frontal polymerization: Synthesis, characterization and optical properties

Frontal polymerization was successfully used to prepare two series of copolymers from a tetraphenylporphyrin-containing monomer (TPP-TEG-MA) and poly(ethylene glycol) methyl ether acrylate (PEGMA) or di(ethylene glycol) methyl ether methacrylate (DEGMA). Tricaprylmethylammonium (Aliquat) persulfate (APSO) was used as radical initiator to obtain highly fluorescent hydrogels with different chromophore contents. The obtained hydrogels, PEGTPP and DEGTPP series, were characterized by FT-IR spectroscopy, and the successful incorporation of TPP-TEG-MA monomer into the polymer backbone was observed. Their thermal properties were determined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The swelling behavior of the obtained hydrogels was measured at 25 °C and pH = 7. The swelling ratio increased until equilibrium was reached after 24 h. Furthermore, the pH and temperature responses of the obtained hydrogels were measured. The optical properties of these materials were studied by absorption and fluorescence spectroscopies. They exhibited an absorption band at 418 nm (Soret band) and an emission band at 653 nm, which are typical of the porphyrin moiety.

Visualization of Polymer Dynamics in Cellulose Nanocrystal Matrices Using Fluorescence Lifetime Measurements.

Polymer nanocomposites containing self-assembled cellulose nanocrystals (CNCs) are ideal for advanced applications requiring both strength and toughness as the helicoidal structure of the CNCs deflects crack propagation and the polymer matrix dissipates impact energy. However, any adsorbed water layer surrounding the CNCs may compromise the interfacial adhesion between the polymer matrix and the CNCs, thus impacting stress transfer at that interface. Therefore, it is critical to study the role of water at the interface in connecting the polymer dynamics and the resulting mechanical performance of the nanocomposite. Here, we explore the effect of polymer confinement and water content on polymer dynamics in CNC nanocomposites by covalently attaching a fluorogenic water-sensitive dye to poly(diethylene glycol methyl ether methacrylate) (PMEO2MA), to provide insights into the observed mechanical performance. Utilizing fluorescence lifetime imaging microscopy (FLIM), the lifetime of dye fluorescence decay was measured to probe the polymer chain dynamics of PMEO2MA in CNC nanocomposite films. The PMEO2MA chains experienced distinct regions of differing dynamics within Bouligand structures. A correlation was observed between the average fluorescence lifetime and the mechanical performance of CNC films, indicating that polymer chains with high mobility improved the strain and toughness. These studies demonstrated FLIM as a method to investigate polymer dynamics at the nanosecond timescale that can readily be applied to other composite systems.

Methacrylate and Styrene Block Copolymer Synthesis by Cu‐Mediated Chain Extension of Acrylate Macroinitiator in a Semibatch Reactor

AbstractA process for the well‐controlled growth of acrylates by Cu‐mediated polymerization has been developed, with macroinitiator synthesized continuously in a copper tubular reactor and subsequently chain‐extended in a semibatch reactor without additional copper. Extending this process to methacrylates and styrene, however, has proven difficult due to a significant reduction in reaction rate. This barrier has been overcome by chain‐extending the low molecular weight (Mn of 760 g mol–1) poly(methyl acrylate) macroinitiator with methacrylates and styrene using PMDETA (N,N,N′,N″,N″‐pentamethyldiethylenetriamine) as ligand. Methyl methacrylate conversions of >80% at 70 °C and diethylene glycol methyl ether methacrylate conversions of >90% at room temperature are achieved in 4 h, with the same room temperature conditions successfully applied for controlled chain extensions with butyl methacrylate. Although styrene conversions are slightly lower (60–70%) over 4 h at 85 °C, the rates achieved are substantially higher than achieved in other studies. Hydrophobic–hydrophilic triblock structures are produced through sequential monomer feeds to the semibatch reactor, keeping total reaction time to less than 5 h. The ability to incorporate methacrylates and/or styrene into structured block polymers greatly extends the range of products that can be efficiently synthesized with low copper levels by this process.

Thermoresponsive polymer assemblies via variable temperature liquid-phase transmission electron microscopy and small angle X-ray scattering

Herein, phase transitions of a class of thermally-responsive polymers, namely a homopolymer, diblock, and triblock copolymer, were studied to gain mechanistic insight into nanoscale assembly dynamics via variable temperature liquid-cell transmission electron microscopy (VT-LCTEM) correlated with variable temperature small angle X-ray scattering (VT-SAXS). We study thermoresponsive poly(diethylene glycol methyl ether methacrylate) (PDEGMA)-based block copolymers and mitigate sample damage by screening electron flux and solvent conditions during LCTEM and by evaluating polymer survival via post-mortem matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI-IMS). Our multimodal approach, utilizing VT-LCTEM with MS validation and VT-SAXS, is generalizable across polymeric systems and can be used to directly image solvated nanoscale structures and thermally-induced transitions. Our strategy of correlating VT-SAXS with VT-LCTEM provided direct insight into transient nanoscale intermediates formed during the thermally-triggered morphological transformation of a PDEGMA-based triblock. Notably, we observed the temperature-triggered formation and slow relaxation of core-shell particles with complex microphase separation in the core by both VT-SAXS and VT-LCTEM.

Thermoresponsive poly(di(ethylene glycol) methyl ether methacrylate)-ran-(polyethylene glycol methacrylate) graft copolymers exhibiting temperature-dependent rheology and self-assembly

Graft copolymers with brush-type architectures are explored containing poly(ethylene glycol) methacrylates copolymerized with “thermoresponsive” monomers which impart lower critical solution temperatures to the polymer. Initially, the chemical structure of the thermoresponsive polymer is explored, synthesizing materials containing N-isopropyl acrylamide, N,N-diethyl acrylamide and diethylene glycol methyl ether methacrylate. Thermoresponsive graft-copolymers containing di(ethylene glycol) methyl ether methacrylate (DEGMA) exhibited phase transition temperature close to physiological conditions (ca 30 °C). The effect of polymer composition was explored, including molecular weight, PEG-methacrylate (PEGMA) terminal functionality and PEGMA/DEGMA ratios. Molecular weight exhibited complex relationships with phase behavior, where lower molecular weight systems appeared more stable above lower critical solution temperatures (LCST), but a lower limit was identified. PEGMA/DEGMA feed was able to control transition temperature, with higher PEGMA ratios elevating thermal transition. It was found that PEGMA terminated with methoxy functionality formed stable colloidal structures above LCST, whereas those the hydroxy termini generally formed two-phase sedimented systems when heated. Two thermoresponsive DEGMA-based graft polymers, poly(PEGMA7-ran-DEGMA170) and poly(PEGMA1-ran-DEGMA38), gave interesting temperature-dependent rheology, transitioning to a viscous state upon heating. These materials may find application in forming thermothickening systems which modify rheology upon exposure to the body’s heat.

Comestible curcumin: From kitchen to polymer chemistry as a photocatalyst in metal-free ATRP of (meth)acrylates

The article presents an application of curcumin, a widely available and cost-effective organic dye, to control visible-light mediated ATRP. A two-component photocatalytic system composed of curcumin and an amine-based electron donor activates alkyl bromide and controls radical polymerizations by a reductive quenching pathway. The polymerizations of various types of (meth)acrylates were performed under blue LED irradiation (λmax = 460 nm, 5 mW cm−2). The effect of electron donor type, solvent, photocatalyst and electron donor concentration, target degree of polymerization (DPtarget) etc. on the metal-free ATRP of methyl methacrylate (MMA) and poly(ethylene glycol) methyl ether methacrylate (OEGMA500) was systematically investigated to optimize the polymerization conditions. Moreover, comestible curcumin of four different brands available in the market as kitchen spices was used, which makes this approach economical (∼0.04 € for 15 g of turmeric). In order to increase the applicability of the curcumin-based polymerization strategy, the concept was extended to the polymerization of other methacrylates – butyl methacrylate (nBMA), di(ethylene glycol) methyl ether methacrylate (DEGMA), 2-(dimethylamino)ethyl methacrylate (DMAEMA), and acrylates i.e. poly(ethylene glycol) methyl ether acrylate (OEGA480), n-butyl acrylate (nBA) and 2-hydoxyethyl acrylate (HEA). In situ chain extension experiment demonstrated the preservation of chain-end functionality, enabling the facile synthesis of well-controlled copolymers.

Synthesis and Self-Assembly of Thermoresponsive Biohybrid Graft Copolymers Based on a Combination of Passerini Multicomponent Reaction and Molecular Recognition.

Amphiphilic graft copolymers exhibit fascinating self-assembly behaviors. Their molecular architectures significantly affect the morphology and functionality of the self-assemblies. Considering the potential application of amphiphilic graft copolymers in the fabrication of nanocarriers, it is essential to synthesize well-defined graft copolymers with desired functional groups. Herein, the Passerini reaction and molecular recognition are introduced to the synthesis of functional thermoresponsive graft copolymers. A bifunctional monomer 2-((adamantan-1-yl)amino)-1-(4-((2-bromo-2-methylpropanoyl)oxy)phenyl)-2-oxoethyl methacrylate (ABMA) with a bromo group for atom transfer radical polymerization (ATRP) and an adamantyl group for molecular recognition is synthesized through the Passerini reaction. The graft copolymers are prepared by reversible addition-fragmentation transfer (RAFT) copolymerization of ABMA and oligo(ethylene glycol) methyl ether methacrylate (OEGMA) followed by RAFT end group removal and ATRP of di(ethylene glycol)methyl ether methacrylate (DEGMA) initiated by the ABMA units. The graft copolymer P(OEGMA-co-ABMA)-g-PDEGMA can be functionalized with β-cyclodextrin modified peptides, affording a thermoresponsive biohybrid graft copolymer. At a temperature above its lower critical solution temperature, the biohybrid graft copolymer self-assembles into peptide-modified polymersomes.

A library of thermoresponsive PEG‐based methacrylate homopolymers: How do the molar mass and number of ethylene glycol groups affect the cloud point?

AbstractIn this study, a novel library of thermoresponsive homopolymers based on poly (ethylene glycol) (EG) (m)ethyl ether methacrylate monomers is presented. Twenty‐seven EG based homopolymers were synthesized and three parameters, the molar mass (MM), the number of the ethylene glycol groups in the monomer, and the chemistry of the functional side group were varied to investigate how these affect their thermoresponsive behavior. The targeted MMs of these polymers are varied from 2560, 5000, 8200 to 12,000 g mol−1. Seven PEG‐based monomers were investigated: ethylene glycol methyl ether methacrylate (MEGMA), ethylene glycol ethyl ether methacrylate (EEGMA), di(ethylene glycol) methyl ether methacrylate (DEGMA), tri(ethylene glycol) methyl ether methacrylate (TEGMA), tri(ethylene glycol) ethyl ether methacrylate (TEGEMA), penta(ethylene glycol) methyl ether methacrylate (PEGMA), nona(ethylene glycol) methyl ether methacrylate (NEGMA). Homopolymers of 2‐(dimethylamino) ethyl methacrylate (DMAEMA) were also synthesized for comparison. The cloud points of these homopolymers were tested in different solvents and it was observed that it decreases as the number of EG group was decreased or the MM increased. Interestingly, the end functional group (methoxy or ethoxy) of the side group has an effect as well and is even more dominant than the number of EG groups.

Geometrical Constraints of Poly(diethylene glycol methyl ether methacrylate) Brushes on Spherical Nanoparticles and Cylindrical Nanowires: Implications for Thermoresponsive Brushes on Nanoobjects

We report on the polymerization kinetics of thermoresponsive poly(diethylene glycol methyl ether methacrylate) (PDEGMA) brushes, which are used in novel cell release coating, on curved spherical si...

Poly(diethylene glycol methylether methacrylate) Brush-Functionalized Anodic Alumina Nanopores: Curvature-Dependent Polymerization Kinetics and Nanopore Filling.

We report on the synthesis and characterization of poly(diethylene glycol methylether methacrylate) (PDEGMA) brushes by surface-initiated atom transfer radical polymerization inside ordered cylindrical nanopores of anodic aluminum oxide with different pore radii between 20 and 185 nm. In particular, the dependence of polymerization kinetics and the degree of pore filling on the interfacial curvature were analyzed. On the basis of field emission scanning electron microscopy data and thermal gravimetric analysis (TGA), it was concluded that the polymerization rate was faster at the pore orifice compared to the pore interior and also as compared to the analogous reaction carried out on flat aluminum oxide substrates. The apparent steady-state polymerization rate near the orifice increased with decreasing pore size. Likewise, the overall apparent polymerization rate estimated from TGA data indicated stronger confinement for pores with increased curvature as well as increased mass transport limitations due to the blockage of the pore orifice. Only for pores with a diameter to length ratio of ∼1, PDEGMA brushes were concluded to grow uniformly with constant thickness. However, because of mass transport limitations in longer pores, incomplete pore filling was observed, which leads presumably to a PDEGMA gradient brush. This study contributes to a better understanding of polymer brush-functionalized nanopores and the impact of confinement, in which the control of polymer brush thickness together with grafting density along the nanopores is key for applications of PDEGMA brushes confined inside nanopores.

Preparation and Characterization of Thermoresponsive PEG-Based Injectable Hydrogels and Their Application for 3D Cell Culture.

We report here the synthesis of a series of ethylene glycol-based triblock copolymers containing a hydrophilic middle segment of poly(ethylene glycol) methyl ether methacrylate (PEGMA) and two temperature-responsive segments of diethylene glycol methyl ether methacrylate (DEGMA) at both ends via the reversible addition-fragmentation chain-transfer (RAFT) polymerization. While the corresponding temperature-responsive homopolymer (PDEGMA) and the diblock copolymer (PDEGMA-b-PPEGMA) could not form a gel, the triblock copolymers (PDEGMA-b-PPEGMA-b-PDEGMA) could form a physical gel at certain concentrations and at temperatures above the lower critical solution temperature (LCST). This sol-gel transition is fully reversible and can be repeated several times. Depending on the chain length of the middle block and two end blocks, a physical gel could be formed at a minimum polymer concentration of 5 wt %. In addition, a mechanically strong gel could be easily formed within 5 s at the maximum concentration of 20 wt % and at a temperature of 37 °C. Considering the good cell compatibility and soft rubbery nature of the triblock copolymers, they can potentially be used as injectable scaffold for cell culture and tissue engineering applications.