UV-initiated Free Radical Polymerization Research Articles

Double polymer networks comprising covalent and hydrogen-bonded cross-links

We report the investigation of rubbery double networks that are based on poly(n-butyl acrylate) (BA) backbones and feature either non-covalent or covalent cross-links. The polymers for the supramolecular network were prepared by reversible addition−fragmentation chain-transfer polymerization of n-butyl acrylate and up to 10 mol% of the self-complementary hydrogen bonding motif 2-ureido-4[1H]pyrimidinone (UPy), which dimerizes into supramolecular cross-links. The covalent polymer network was synthesized by UV-initiated free-radical polymerization of BA and up to 5 mol% of the difunctional cross-linker 1,4-butanediol diacrylate, either separately, or after imbibing films of the supramolecular network with the reaction mixture for the covalent network. The combination of the two network types affords materials that show features of both single networks. The co-existence of a static and a dynamic network affords materials that owe their high thermal stability and creep resistance to the covalent network, and their high extensibility and healability to the supramolecular network.

Design and Gas Separation Performance of Imidazolium Poly(ILs) Containing Multivalent Imidazolium Fillers and Crosslinking Agents.

This work introduces a series of vinyl-imidazolium-based polyelectrolyte composites, which were structurally modified via impregnation with multivalent imidazolium-benzene ionic liquids (ILs) or crosslinked with novel cationic crosslinkers which possess internal imidazolium cations and vinylimidazolium cations at the periphery. A set of eight [C4vim][Tf2N]-based membranes were prepared via UV-initiated free radical polymerization, including four composites containing di-, tri-, tetra-, and hexa-imidazolium benzene ILs and four crosslinked derivatives which utilized tri- and tetra- vinylimidazolium benzene crosslinking agents. Structural and functional characterizations were performed, and pure gas permeation data were collected to better understand the effects of “free” ILs dispersed in the polymeric matrix versus integrated ionic crosslinks on the transport behaviors of these thin films. These imidazolium PIL:IL composites exhibited moderately high CO2 permeabilities (~20–40 Barrer), a 4–7× increase relative to corresponding neat PIL, with excellent selectivities against N2 or CH4. The addition of imidazolium-benzene fillers with increased imidazolium content were shown to correspondingly enhance CO2 solubility (di- < tri- < tetra- < hexa-), with the [C4vim][Tf2N]: [Hexa(Im+)Benz ][Tf2N] composite showing the highest CO2 permeability (PCO2 = 38.4 Barrer), while maintaining modest selectivities (αCO2/CH4 = 20.2, αCO2/N2 = 23.6). Additionally, these metrics were similarly improved with the integration of more ionic content bonded to the polymeric matrix; increased PCO2 with increased wt% of the tri- and tetra-vinylimidazolium benzene crosslinking agent was observed. This study demonstrates the intriguing interactions and effects of ionic additives or crosslinkers within a PIL matrix, revealing the potential for the tuning of the properties and transport behaviors of ionic polymers using ionic liquid-inspired small molecules.

Screening Platform for Identification of Suitable Monomer Mixtures Able To Form Thin-Film Coatings on Polyurethanes by UV-Initiated Free Radical Polymerization

Screening platforms have become a valuable tool for exploring large libraries of surface chemistries helping the discovery of new materials for especially biological applications. Methods applied i...

Study of Biofilm Growth on Slippery Liquid-Infused Porous Surfaces Made from Fluoropor.

Undesired growth of biofilms represents a fundamental problem for all surfaces in long-term contact with aqueous media. Mature biofilms resist most biocide treatments and often are a pathogenic threat. One way to prevent biofilm growth on surfaces is by using slippery liquid-infused porous surfaces (SLIPS). SLIPS consist of a porous substrate which is infused with a lubricant immiscible with the aqueous medium in which the bacteria are suspended. Because of the lubricant, bacteria cannot attach to the substrate surface and thus formation of the biofilm is prevented. For this purpose, we manufactured substrates with different porosity and surface roughness values via UV-initiated free-radical polymerization in Fluoropor. Fluoropor is a class of highly fluorinated bulk-porous polymers with tunable porosity, which we recently introduced. We investigated the growth of the biofilm on the substrates, showing that a reduced surface roughness is beneficial for the reduction of biofilm growth. Samples of low roughness effectively reduced Pseudomonas aeruginosa biofilm growth for 7 days in a flow chamber experiment. The low-roughness samples also become transparent when infused with the lubricant, making such surfaces ideal for real-time observation of biofilm growth by optical examination.

Mechanically improved sol-gel derived methacrylate-siloxane hybrid materials with urethane linkage

Ultraviolet (UV)-curable and highly condensed (>86%) methacrylate phenyl oligo-siloxane (MPO) was synthesized by non-hydrolytic sol–gel condensation reaction between methacrylate and phenyl silane precursor. The MPO resin was then cured by an UV-initiated free-radical polymerization to fabricate a transparent (>90% at 550 nm) methacrylate–siloxane hybrid material (methacrylate hybrimer). An urethane butanediol dimethacrylate (UBDM) monomer was synthesized as a cross-linker into the methacrylate hybrimer networks without micro-phase separation. The UBDM increased methacrylate conversion and mechanical properties due to the hydrogen bonding of the urethane linkage. The hardness, modulus, and strength were improved by UBDM insertion, the flexibility was even increased with 140% elongation, compared to neat MH. In addition, a storage modulus related to the thermo-mechanical properties was also enhanced by a denser cross-linkage with the urethane linkage.

Highly Conductive, Photolithographically Patternable Ionogels for Flexible and Stretchable Electrochemical Devices.

An ionic conducting membrane is an essential part in various electrochemical devices including ionic actuators. To miniaturize these devices, micropatterns of ionic conducting membrane are desired. Here, we present a novel type of ionogel that can be patterned using standard photolithography and soft imprinting lithography. The ionogel is prepared in situ by UV-initiated free-radical polymerization of thiol acrylate precursors in the presence of ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. The resultant ionogel is very flexible with a low Young's modulus (as low as 0.23 MPa) and shows a very high ionic conductivity (up to 2.4 × 10-3 S/cm with 75 wt % ionic liquid incorporated) and has a reactive surface due to the excess thiol groups. Micropatterns of ionogel are obtained by using the thiol acrylate ionogel solution as an ionic conducting photoresist with standard photolithography. Water, a solvent immiscible with ionic liquid, is used as the photoresist developer to avoid complete removal of ionic liquid from thin micropatterns of the ionogel. By taking advantage of the reactive surface of ionogels and the photopatternability, ionogels with complex three-dimensional microstructure are developed. The surface of the ionogels can also be easily patterned using UV-assisted soft imprinting lithography. This new type of ionogels may open up for building high-performance flexible electrochemical microdevices.

Itaconate based polyesters: Selectivity and performance of esterification catalysts

The performance of different esterification catalysts was studied for the use in synthesis of renewable polyesters from dimethyl itaconate (DMI), dimethyl succinate (DMS) and 1,4-butanediol (BD). Itaconic acid and derivatives such as DMI are interesting monomers because of their multiple functionalities and previous work has shown great potential. However, the multiple functionalities also pose challenges to avoid side reactions such as thermally initiated, premature, radical crosslinking and/or isomerization of the 1,1-disubstituted unsaturation. Additionally, the two carboxylic acids have inherently different reactivity. One key factor to control reactions with IA is to understand the performance of different catalysts. In this study, six esterification catalysts were investigated; immobilized Candida antarctica lipase B (CalB), titanium(IV)butoxide (Ti(OBu)4), p-toluenesulfonic acid (pTSA), sulfuric acid (H2SO4), 1,8-diazabicycloundec-7-ene (DBU), and 1,5,7-triazabicyclodec-5-ene (TBD). CalB and Ti(OBu)4 were selected for further characterization with appreciable differences in catalytic activity and selectivity towards DMI. CalB was the most effective catalysts and was applied at 60 °C while Ti(OBu)4 required 160 °C for a reasonable reaction rate. CalB was selective towards DMS and the non-conjugated side of DMI, resulting in polyesters with itaconate-residues mainly located at the chain ends, while Ti(OBu)4 showed low selectivity, resulting in polyesters with more randomly incorporated itaconate units. Thermal analysis of the polyesters showed that the CalB-catalyzed polyesters were semi-crystalline, whereas the Ti(OBu)4-catalyzed polyesters were amorphous, affirming the difference in monomer sequence. The polyester resins were crosslinked by UV-initiated free radical polymerization and the material properties were evaluated and showed that the crosslinked materials had similar material properties. The films from the polyester resins catalyzed by CalB were furthermore completely free from discoloration whereas the film made from the polyester resins catalyzed with Ti(OBu)4 had a yellow color, caused by the catalyst. Thus, it has been shown that CalB can be used to attain sustainable unsaturated polyesters resins for coating applications, exhibiting equally good properties as resins obtained from traditional metal-catalysis.

Crosslinked Microgels as Platform for Hydrolytic Catalysts

In an effort to develop biomimetic glycosyl transfer catalysts, a polymerization protocol was developed that is applicable to the synthesis of crosslinked microgels via UV-initiated free radical polymerization of miniemulsions at ambient temperature and below. The catalytic activity of the microgels derived from butyl acrylate, EGDMA, and a catalyst-precursor ligand was established using the hydrolysis of 4-methylumbelliferyl β-d-galactopyranoside as a model reaction. The microgel-catalyzed hydrolysis was up to 3 × 105-fold accelerated over the background reaction and notably 38-fold faster than the hydrolysis catalyzed by its low molecular weight analog. Dynamic light scattering analysis demonstrated mean hydrodynamic diameters of the particles between 210 and 280 nm and chemical stability of the particles in aqueous solution between pH 1 and 13. A bell-shaped correlation between catalytic proficiency and material rigidity was observed that peaks at 40 mol % of crosslinking content of the microgel.

Abstract A01: Mechanical properties of matrices strongly influence spontaneous tumor dormancy and responses to chemotherapy in a 3D model of metastasis

Abstract Background: Distant metastasis is the major cause of breast cancer (BrCa)-related mortality with half of the disseminated disease emerging clinically after 5 or more years of seeming “cure” of the primary tumor. The lack of relevant accessible model systems for metastasis has hindered our understanding of the molecular basis of metastasis and the development of therapies against these lethal outgrowths. Furthermore, standard culture techniques employ rigid surfaces that are associated with driving even non-transformed cells towards aggressive phenotypes. To address this gap, we previously developed an innovative all-human 3D ex vivo hepatic microphysiological system (MPS) that faithfully reproduces human liver physiology. This MPS also enables spontaneous dormancy in subpopulations of, but not all, BrCa cells. In this study, we query this subpopulation effect by examining matrix stiffness on the occurrence of spontaneous tumor dormancy; we compared a conventional polystyrene material (~3 GPa) to a PEG-based hydrogel biomaterial (~100 kPa) that more closely approaches the malleable physiologic consistency of the liver (~600 Pa). We hypothesized that providing a more physiological environment would promote BrCa dormancy and provide increased protection from chemotherapy as observed in patients, enabling the study of this elusive but critical stage in cancer progression. Methods: A hepatic all-human MPS was retrofitted with hydrogel scaffolding in place of the standard polystyrene. Hydrogel scaffolds were formed by micromolding with polydimethylsiloxane (PDMS) and UV-initiated free radical polymerization. Prior to polymerization, a SynKRGD peptide sequence was conjugated to PEGDa via Michael-type addition to aid in hepatocyte interaction with the hydrogel. The MPS incorporated de-identified excess primary human hepatocytes and non-parenchymal cells (NPCs) isolated from therapeutic patient liver resections. MDA-MB-231 BrCa cells (RFP labeled) were seeded on day 3 and allowed time to intercalate into the hepatic tissue prior to treatment with chemotherapies on day 7 for 72 h. Proliferation was determined by RFP quantification, Ki67 staining and EdU incorporation. Hepatic tissue function was monitored by protein catabolism (urea), metabolism (glucose, CYP P450) and injury markers (AST, ALT). Multiplex bead-based immunoassays of 77 analytes were used to assess physiologic tissue health, cancer markers and inflammatory signals as well as to discern signaling networks within the metastatic niche. Results: The use of hydrogels in this system further fostered spontaneous BrCa quiescent dormancy, as indicated by a lower presence of BrCa cells and decreased proliferation. Hepatic tissue in hydrogel scaffolds secreted lower levels of pro-inflammatory analytes and NPCs were more responsive to inflammatory stimuli. As a result, high dose chemotherapy that targets proliferating cells was less effective against BrCa cells within tissues supported by hydrogel scaffolds. Interestingly, proliferation (emergence) of BrCa cells was observed following treatment with the lower doses of chemotherapy. The lower doses may be damaging the hepatic tissue, causing cellular stress and activation of the more responsive NPCs, which in turn secrete signals that promote the outgrowth and emergence of BrCa cells. Conclusion: These data suggest that using hydrogel scaffolds to more closely align the physiologic and mechanical properties of the macro-environment imparts a healthier hepatic microenvironment. This allowed for interesting insights into the effect of different chemotherapeutic doses on dormant BrCa cells, and highlights this all-human hepatic model of metastasis fitted with hydrogel scaffolds as a critical tool in the assessment and development of therapeutic strategies to target dormant metastatic BrCa. Citation Format: Amanda M. Clark, Sarah E. Wheeler, Carissa L. Young, Jaclyn Shepard Neiman, Venkateswaran Pillai, Linda Stockdale, Donna Stolz, Douglas A. Lauffenburger, Raman Venkataramanan, Linda G. Griffith, Alan Wells. Mechanical properties of matrices strongly influence spontaneous tumor dormancy and responses to chemotherapy in a 3D model of metastasis. [abstract]. In: Proceedings of the AACR Special Conference on Engineering and Physical Sciences in Oncology; 2016 Jun 25-28; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2017;77(2 Suppl):Abstract nr A01.

Self-Assembly Directed Organization of Nanodiamond During Ionic Liquid Crystalline Polymer Formation.

The UV-initiated free radical polymerization of a lyotropic mesophase prepared by co-assembly of an aqueous mixture of an ionic liquid (IL) monomer, 3-decyl-1-vinylimidazolium chloride, in a dimethyl sulfoxide dispersion of an IL-monomer nanodiamond conjugate yields a well-ordered 2D hexagonally structured network-polymer composite. The IL monomer is covalently bound to carboxylated detonation diamond via ester-linked 3-decyl-1-vinylimidazolium bromide. Successful preparation of the amphiphile-functionalized nanodiamond is determined by ATR/FT-IR, thermogravimetric analysis, and small-angle X-ray scattering (SAXS). Mesophase and composite structure are evaluated by SAXS, revealing a columnar architecture composed of amphiphilic ionic liquid cylinders containing solvent-rich cores. Self-assembly directed site localization of the nanodiamond positions the particles in the alkyl chain continuum upon polymerization. The composite reversibly swells in ethanol allowing structural variation and modulation of the nanoparticle internal packing arrangement. This work demonstrates that through careful molecular design, self-organization and site-directed assembly of nanodiamond into chemically distinct regions of a nanostructured organogel can be achieved.

Stimulus-responsiveness and methyl violet release behaviors of poly(NIPAAm-co-AA) hydrogels chemically crosslinked with β-cyclodextrin polymer bearing methacrylates

To fabricate thermo- and pH-sensitive hydrogels functionalized with β-cyclodextrin (β-CD) moieties, β-CD polymer bearing methacrylate (CDP-g-GMA) used as a reactive and functional crosslinker was synthesized, and then copolymerized with N-isopropylacrylamide (NIPAAm) and acrylic acid (AA) in aqueous solution via UV-initiated free radical polymerization. The stimulus-responsiveness of the resultant hydrogels has been carried out by measuring the swelling ratio at different temperatures and pH values. The results showed that the thermo- and pH-sensitivities of the produced hydrogels were significantly dependent on the compositions of the hydrogels, and the dual sensitivities exhibited good reversible process. The interior morphology observed by SEM exhibited that the pore size of the hydrogels could be tailored by pH of the local medium. Using a water-soluble cationic dye methyl violet (MV) as a model drug, MV loading and release profiles of the hydrogels as potential drug controlled release carriers were evaluated. The MV release rate from CD-functionalized hydrogels was much slower than that from the hydrogel without β-CDs at both pH 2.0 and pH 7.4. The release of MV from CD-functionalized hydrogels at pH 2.0 was faster than that at pH 7.4, the release kinetics of MV from the CD-functionalized hydrogels displayed a sustained release profile, and the release mechanism followed Fickian diffusion.

Assessment of the safety, targeting, and distribution characteristics of a novel pH-sensitive hydrogel

In our previous study, we synthesized a pH-sensitive hydrogel based on poly (ɛ-caprolactone) (PCL), Pluronic (Poloxamer) and methacrylic acid (MAA) using UV-initiated free-radical polymerization. In the present study, we evaluated the safety of the obtained GMA–PCFC–GMA copolymer and a P(CFC–MAA–MEG) hydrogel both in vitro and in vivo. The pharmacokinetics study and distribution characteristics of dexamethasone in rat blood and mouse colon were investigated in detail. The in vitro toxicity of the GMA–PCFC–GMA copolymer was evaluated using a cell viability assay with HEK293 cells. An acute oral toxicity test was conducted by orally administering mice with a total of 10,000mg/kg body weight of the P(CFC–MAA–MEG) hydrogel. The mice were then observed continuously for 14 days. After which, they were sacrificed and their blood collected for routine blood and serum chemistry tests. Pharmacokinetic and colonic tissue distribution studies were conducted using high-performance liquid chromatography to detect the concentration of dexamethasone in rat blood and mouse colon tissue. All of the results indicated that both the GMA–PCFC–GMA copolymer and P(CFC–MAA–MEG) hydrogel were nontoxic. Moreover, the hydrogel significantly enhanced the colon-targeting behavior of dexamethasone. These results suggested that the novel hydrogel has great potential in colon-targeted drug delivery.

Patterning a π-conjugated polyelectrolyte through sequential polymerization of a bifunctional ionic liquid monomer

An electronically conductive polyelectrolyte is prepared by the sequential polymerization of a bifunctional imidazolium-based ionic liquid (IL) monomer, composed of a thienyl and vinyl containing cation paired with a tetrafluoroborate anion. In the first step, potentiodynamic electropolymerization of the thienyl moiety forms a cationic polyalkylthiophene that is soluble in select organic solvents. Cyclic voltammetry (CV) was used to determine the polymer p-doping potential (0.31 V) and the bipolaronic state (1.49 V). The polymer exhibits electrochromism, converting from red in the neutral state (λmax = 443 nm) to dark blue in the polaronic state (λmax = 819 nm). The solution-processable polymer can be cast into a film, masked and patterned by UV-initiated free radical polymerization of the vinyl moiety. Small-angle X-ray scattering (SAXS) revealed that the insoluble crosslinked polyalkylthiophene–polyvinylimidazolium adopts a lamellar structure with a lattice spacing of 3.3 nm. Four-probe d.c. conductivity measurements determined the de-doped electrical conductivity was 1.0 × 10−2 S/cm. The results underscore the importance of the anion in controlling the polymerization of IL monomers.

Slippery Liquid-Infused Porous Surfaces Showing Marine Antibiofouling Properties

Marine biofouling is a longstanding problem because of the constant challenges placed by various fouling species and increasingly restricted environmental regulations for antifouling coatings. Novel nonbiocidal strategies to control biofouling will necessitate a multifunctional approach to coating design. Here we show that slippery liquid-infused porous surfaces (SLIPSs) provide another possible strategy to obtaining promising antifouling coatings. Microporous butyl methacrylate-ethylene dimethacrylate (BMA-EDMA) surfaces are prepared via UV-initiated free-radical polymerization. Subsequent infusion of fluorocarbon lubricants (Krytox103, Krytox100, and Fluorinert FC-70) into the porous microtexture results in liquid-repellent slippery surfaces. To study the interaction with marine fouling organisms, settlement of zoospores of the alga Ulva linza and cypris larvae of the barnacle Balanus amphitrite is tested in laboratory assays. BMA-EDMA surfaces infused with Krytox103 and Krytox100 exhibit remarkable inhibition of settlement (attachment) of both spores and cyprids to a level comparable to that of a poly(ethylene glycol) (PEG)-terminated self-assembled monolayer. In addition, the adhesion strength of sporelings (young plants) of U. linza is reduced for BMA-EDMA surfaces infused with Krytox103 and Krytox100 compared to pristine (noninfused) BMA-EDMA and BMA-EDMA infused with Fluorinert FC-70. Immersion tests suggest a correlation between the stability of slippery coatings in artificial seawater and fouling resistance efficacy. The results indicate great potential for the application of this concept in fouling-resistant marine coatings.

Novel Biodegradable pH/Thermosensitive Hydrogels: Part 1. Preparation and Characterization

A series of biodegradable and pH/thermosensitive hydrogels based on monomethoxyl poly(ethylene glycol) (MPEG), poly(ϵ-caprolactone) (PCL), methylacrylic acid (MAA), and N-Isopropylacrylamide (NIPAAm) were prepared by UV-initiated free radical polymerization method. Swelling behavior and hydrolytic degradable behavior in aqueous medium with different pH values and pH/thermosensitivity of the hydrogels were studied in detail. The prepared biodegradable pH/thermo-sensitive hydrogels based on PCL, MPEG, MAA, and NIPAAm may have great potential application in smart drug delivery system.

Synthesis and characterization of pH and temperature sensitive hydrogel based on poly(N-isopropylacrylamide), poly(ɛ-caprolactone), methylacrylic acid, and methoxyl poly(ethylene glycol)

In this paper, a novel biodegradable and pH/thermo-sensitive hydrogel based on poly(ɛ-caprolactone), methoxyl poly(ethylene glycol), methylacrylic acid and N-isopropylacrylamide was prepared by UV-initiated free radical polymerization. The hydrogels were characterized by Fourier transforms infrared ray. The thermal responsibility was investigated with the help of differential scanning calorimetry. Swelling behavior in aqueous medium with different pH value was studied in detail. When the pH value of the aqueous medium was increased from 1.2 to 7.2, the swelling ratio of the hydrogels increased accordingly. The morphology was observed by scanning electron microscopy, and the hydrolytic degradation behavior in different aqueous media (pH 1.2 and pH 7.2) was also investigated in detail. The prepared biodegradable pH/thermo-sensitive hydrogel based on poly(ɛ-caprolactone), methoxyl poly(ethylene glycol), methylacrylic acid and N-isopropylacrylamide hold great promise in the development of a smart drug delivery system.

Novel polymeric solid acid catalysts for cellulose hydrolysis

Novel solid polymeric catalysts consisting of polymer chains have been synthesized to facilitate cellulose dissolution and catalyze its hydrolysis. Poly(styrene sulfonic acid) (PSSA) polymer chains have been grown from the substrate surface and used to catalyze biomass hydrolysis. Neighboring poly(vinyl imidazolium chloride) ionic liquid (PIL) polymer chains, also grown from the substrate surface, help solubilize lignocellulosic biomass and enhance the catalytic activity of the PSSA chains. The PSSA chains were synthesized via surface initiated atom-transfer radical polymerization (ATRP) whereas the adjacent PIL chains were synthesized via UV-initiated free radical polymerization. These novel polymeric solid acid catalysts demonstrate over 97% and 32% total reducing sugar (TRS) yields from cellulose hydrolysis in [EMIM]Cl and aqueous solutions respectively. The dual ATRP and UV-initiated polymerization schemes allow independent variation of the relative ratio of the two nanostructures as well as the chain length and density. This permits optimization of the catalytic activity for cellulose hydrolysis reaction. These catalysts are stable and maintain high catalytic activity after repeated runs.

A 3D porous polymer monolith-based platform integrated in poly(dimethylsiloxane) microchips for immunoassay

In this work, we demonstrate the immunocapture and on-line fluorescence immunoassay of protein and virus based on porous polymer monoliths (PPM) in microfluidic devices. Poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) [poly(GMA-co-EGDMA)] monoliths were successfully synthesized in the polydimethylsiloxane (PDMS) microfluidic channels by in situ UV-initiated free radical polymerization. After surface modification, PPM provides a high-surface area and specific affinity 3D substrate for immunoassays. Combining with well controlled microfluidic devices, the direct immunoassay of IgG and sandwich immunoassay of inactivated H1N1 influenza virus using 5 μL sample has been accomplished, with detection limits of 4 ng mL(-1) and less than 10 pg mL(-1), respectively. The enhanced detection sensitivity is due to both high surface area of PPM and flow-through design. The detection time was obviously decreased mainly due to the shortened diffusion distance and improved convective mass transfer inside the monolith, which accelerates the reaction kinetics between antigen and antibody. This work provides a novel microfluidic immunoassay platform with high efficiency thereby enabling fast and sensitive immunoassay.

Biodegradable, pH-sensitive P(CL-Pluronic-CL-co-MAA-MEG) hydrogel for 5-aminosalicylic acid delivery

In this paper, a series of biodegradable and pH-sensitive hydrogels from Pluronic, poly(e-caprolactone) (PCL), and methylacrylic acid (MAA) polymer matrix was successfully prepared via UV-initiated free radical polymerization method. A scanning electron microscope was adopted to detect the internal microstructure of the prepared hydrogels at different pH values (pH 1.2 and pH 7.2). To investigate the pH-responsivity and hydrolytic degradation characterization of the hydrogel, detailed parameters including MAA and PCL polymers content, PEG content, BIS content and molecular weight of Pluronic have been employed in this work. The in vitro release behavior of hydrophobic 5-aminosalicylic acid drug was investigated in this paper, which indicated that this new kind of hydrogel with good pH-responsivity might have great potential applications in smart drug delivery systems, especially in colon targeting therapy.

Preparation of multisensitive poly (N-isopropylacrylamide-co-acrylic acid)/TiO2 composites for degradation of methyl orange

Composites of poly (N-isopropylacrylamide-co-acrylic acid)/titanium dioxide (TiO2) have been prepared via UV-initiated free radical polymerization. Fourier transform infrared spectra (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), environmental scanning electron microscope (ESEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) are used to study the composition, structure, and morphology of the as-prepared composites. TiO2 is found to be successfully encapsulated in the copolymer in spherical shapes with size of 2.5μm. The thermo- and pH-responsive properties of the composites are observed using dynamic light scattering (DLS). The photocatalytic property of the composites is studied using UV–vis spectrophotometer on the degradation of methyl orange (MO) solution under various pHs and temperatures. Degradation ratio is higher at low pH and increases with increasing temperature above volume phase transition temperature (VPTT).