New degradable, transparent, and elastomeric materials based on PCL are reported in this work. These are block copolymers of PCL with a copolymer of MMA and MDO, i.e. P(MMA‐co‐MDO)‐b‐PCL‐b‐P(MMA‐co‐MDO). A PCL‐based macro‐azoinitiator is used for preparing the block copolymers by free‐radical chemistry. The free‐radical copolymerization of MDO with MMA provides CL units distributed randomly on the PMMA backbone of the second block. This provides the advantage of bringing degradability to the whole system. The detailed structural characterization of the new polymers, their properties evaluation like thermal and mechanical are also reported. The materials are degradable, transparent, and elastomeric depending upon the copolymer composition and block length.
Three pH‐responsive hydrogel families have been synthesized through the photopolymerization of methacrylic acid (MAA) with: i) a poly(ethylene glycol) macromonomer, P(MAA‐co‐PEGMEMA), ii) a poly(propylene glycol) macromonomer, P(MAA‐co‐PPGMEMA), and iii) the two above‐mentioned macromonomers, to give a terpolymer P(MAA‐co‐PEGMEMA‐co‐PPGMEMA). Their swelling properties at pH 7 have been investigated by magnetic resonance imaging (MRI). Equimolecular compositions of both P(MAA‐co‐PEGMEMA) and P(MAA‐co‐PPGMEMA) hydrogels showed the lowest swelling kinetics rates. For P(MAA‐co‐PEGMEMA‐co‐PPGMEMA) hydrogels, the different structure of the side chains established an antagonist effect on the swelling. In addition, from the MRI intensity profiles and taking into account the first stage of the swelling, water diffusion coefficients (D) have been estimated.
Starting from methyl methacrylate (MMA), butyl methacrylate (BMA), allyl methacrylate (AMA), phenoxycarbonyloxy ethyl methacrylate (PCEMA), and functional amines different multifunctional polymethacrylates are accessible. The reactive monomer PCEMA was synthesized starting from 2‐hydroxyethyl methacrylate, and then copolymerized via ATRP with other methacrylates in order to obtain reactive copolymers which were subjected to polymer analogous reactions with different functional amines leading to multifunctional polymethacrylates. These can be used for the preparation of multifunctional surfaces.
A combination of NMP and photoinitiated polymerization is suggested as a new strategy for the synthesis of graft copolymers. First, P(S‐co‐CMS) copolymer backbones with different chloromethyl content are prepared by NMP. The chloro functions are then converted into photosensitive 4‐phenyl pyridinium‐N‐oxide ion functions. Finally, these photoactive polymers are irradiated in the presence of MMA to obtain the graft copolymers. They and their precursors at various stages are characterized by spectroscopy and GPC. It is demonstrated that the irradiation of photoactive polymers in the presence of a hydrogen donors such as THF facilitates the conversion of pyridinium ions to hydroxyl groups.
A novel approach to amphiphilic polymeric Janus micelles based on the protonation/deprotonation process of poly(2‐vinylpyridine)‐block‐poly(ethylene oxide) (P2VP‐b‐PEO) diblock copolymers in THF is presented. It is found that addition of HCl to the micelles solution of P2VP‐b‐PEO copolymers leads to the formation of vesicles. Subsequently mixing a small amount of hydrazine monohydrate with the vesicle solution can induce the dissociation and reorganization of the vesicles into Janus micelles. When HCl is replaced by HAuCl4 precursors, composite Janus particles containing gold in P2VP blocks are obtained.
A series of polystyrene‐block‐poly(n‐butyl methacrylate) (PS‐b‐PnBMA) diblock copolymers (di‐BCPs) with an azobenzene moiety [trans‐4‐methacryloyloxyazobenzene (MOAB)] in the PnBMA segment was prepared by atom transfer radical polymerization (ATRP). P(nBMA‐co‐MOAB) macroinitiators were prepared by activators regenerated by electron transfer (ARGET) ATRP. The MOAB was slightly more reactive than nBMA, resulting in a weak gradient fashion of copolymer. The macroinitiators were subsequently chain‐extended with styrene. Acceleration of the ATRP rate was observed in the presence of a reducing agent. P(nBMA‐co‐MOAB)‐b‐PS di‐BCPs were obtained with relatively narrow molecular weight distributions ( / = 1.16–1.49) and the molecular weights were in good agreement with the theoretical values. The efficiency of photoisomerization of the MOAB units was above 80%. DSC traces showed a single Tg suggesting the block copolymers were miscible before UV irradiation. After UV irradiation, the X‐ray reflectivity measurements showed the beating of two frequencies, indicating the formation of island‐hole structure.
The phase behavior of PCH‐b‐PtBA‐b‐PCH triblock copolymers has been studied. Measurements in the wide‐angle region probed the existence of microphase segregation through variation of block mobility and thermal expansion coefficients. SAXS experiments pointed out that most copolymers present ordered nanostructures, mostly hexagonally packed cylinders, the morphology being confirmed by AFM. An unusual disorder‐to‐order transition is observed in one copolymer synthesized from a macroinitiator with intermediate length and the highest outer‐block molecular weight, whereas none of the copolymers shows an order‐to‐disorder transition upon heating over the temperature range analyzed.
Ethyl cellulose‐graft‐poly(2‐hydroxyethyl methacrylate) (EC‐graft‐PHEMA) graft copolymers were synthesized by atom‐transfer radical polymerization (ATRP) in methanol. The graft copolymers were characterized by means of gel‐permeation chromatography (GPC) and 1H NMR spectroscopy. The kinetic study indicated that the polymerization was controllable. The EC‐graft‐PHEMA copolymers self‐assembled in water into spherical micelles. The morphology of the micelles was characterized by dynamic light scattering (DLS) and transmission electric microscopy (TEM) and the formation process of the micelles was discussed.
The synthesis of a polymeric, photoresponsive drug‐delivery system on the basis of 4‐methylcoumarin‐side‐chain‐functionalized methacrylic copolymers with different degrees of functionalization is reported. Drug‐release experiments in solution indicated a maximum release of 22 µg of 5‐fluorouracil per 1 mg of polymer. Polymer analogous photochemical drug immobilization does not lead to observable intermolecular cross‐linking. Miscibility experiments with PMMA suggest that the bulk polymerization of homogeneous, transparent polymer sheets for intraocular lens fabrication, using MMA as the matrix monomer and incorporating the polymer‐drug conjugates as a functional component, is possible.
Folic acid conjugation onto poly(1‐vinylimidazole) generates imidazolium copolymers for potential receptor‐mediated nonviral gene delivery. Homopolymer quaternization with various tBoc‐protected bromoalkylamines imparts a permanent charge for DNA complexation. Incorporation of primary amine groups provides a site for folic acid conjugation onto imidazolium copolymers. DNA binding, cytotoxicity, and in vitro transfection in HeLa cells reveal structure–property–transfection relationships for the imidazolium copolymers. Luciferase expression assays establish that primary amine conjugation onto imidazolium copolymers up to 30 mol% fails to improve transfection efficiency. In sharp contrast, incorporation of folic acid onto the copolymers improves transfection efficiency 250‐fold.
Well‐defined sulfonated block copolymers were prepared by direct thermolysis with block copolymers of n‐butyl acrylate (nBA) and neopentyl styrene sulfonated (NSS), which were synthesized by Cu‐based living radical polymerization ( <1.20). A simple thermal process for 10 min at 150 °C completely deprotected the neopentyl groups in the poly(NSS) block segment to give fully sulfonated polystyrene backbone. SAXS profile of the block copolymer with 47 wt.‐% of poly(NSS) showed lamella structure, which appeared more clearly with long ranged order after sulfonation of the block copolymer.
The first successful synthesis of conjugated rod–coil star block copolymer, (PF‐b‐P2VP)n, containing conjugated poly[2,7‐(9,9‐dihexylfluorene)] (PF), and coil‐like poly(2‐vinylpyridine) (P2VP) by combining a Suzuki coupling reaction and living anionic polymerization is reported. With increasing methanol content in THF/methanol mixtures (PF‐b‐P2VP)n symmetric star‐block copolymers maintain spherical micelles, but PF‐b‐P2VP asymmetric diblock copolymers vary from spherical micelles to vesicles. Both the absorption and emission spectra of PF‐b‐P2VP blue shift with increasing methanol content, suggesting an “H‐type” aggregation. However, (PF‐b‐P2VP)n star‐block exhibits no shift in absorption but a red shift in the emission spectra, indicating a different type of aggregation. These results suggest the significance of polymer architectures on microphase‐separated morphologies and photophysical properties.
AFM imaging was used to investigate the influence of molecular structure and composition on the formation of Langmuir monolayers by arborescent PS‐graft‐PEO copolymers at the air/water interface. Even without compression, these molecules associate spontaneously at the air/water interface and form stable monolayers that are easily transferred onto solid substrates as Langmuir/Blodgett films. The copolymers either form aggregates with a low association level, large island‐like clusters, or ribbon‐like superstructures. The different behaviors of the copolymers are rationalized in terms of the influence of their composition and of the structure of the arborescent PS cores on the assembly process.
Segmented block copolymers comprised of flexible PEO segments and monodisperse crystallizable bisestertetraamide segments have been synthesized. The influence of the terephthalic units in the soft phase on the transitions and the thermal mechanical and elastic properties are studied. The presence of terephthalic units in the copolymer increases the glass transition temperature of the soft phase by ≈5 °C. The low‐temperature flexibility of the copolymers is improved because of the lower crystallinity and melting temperature of PEO. With the use of terephthalic‐extended PEO segments, segmented block copolymers with low moduli (G' < 15 MPa) and good elastic properties could be obtained.
Double hydrophilic heteroarm star copolymers of poly(methacrylic acid) (PMAA) and poly(ethylene oxide) (PEO) were synthesized via atom‐transfer radical polymerization (ATRP) using the “in‐out” method. The synthesis consisted of three steps. Namely, ATRP was applied to the preparation of a star macroinitiator with PEO arms and a cross‐linked core resulting from the polymerization of divinylbenzene (DVB) in the first step, chain extension with tert‐butyl methacrylate (tBMA) under ATRP conditions, and subsequent hydrolysis of the tert‐butyl groups afforded (PEO)n‐PDVB‐(PMAA)n heteroarm star copolymers with a cross‐linked microgel core. This novel type of double hydrophilic heteroarm star copolymer can be considered as unimolecular micelles with hybrid coronas. The star copolymers exhibited pH‐dependent solubility in water, being soluble at high pH and insoluble at low pH, due to the formation of hydrogen‐bonded complexes between the PEO and PMAA arms. A mixed solution of the heteroarm star copolymer and a PEO‐b‐PQDMA diblock copolymer, where PQDMA is poly(2‐(dimethylamino)ethyl methacrylate) fully quaternized with methyl iodide, remained stable in the whole pH range, and exhibited an intriguing pH‐switchable complexation behavior accompanied with structural rearrangement.
A facile approach to the preparation of functionalized polymeric nanoparticles with UV‐crosslinkable core and bromine‐bearing shell has been developed from the polymerization‐induced self‐assembly of the block copolymers PBNBE‐b‐PCONBI and PBNBE‐b‐PCONBI‐b‐PONBDM. The block copolymers were characterized by means of 1H NMR and GPC. The polymeric nanoparticles with a fixed shell length and varied core lengths were obtained through the control of the molar ratio of monomers in the feed. The micelles were crosslinked using UV‐irradiation, and the characteristics of the polymeric nanoparticles in toluene, THF, or CHCl3 before and after UV irradiation were investigated by means of DLS, UV‐Vis, GPC, AFM, and TEM.
A vinylpyridine block copolymer was prepared by stepwise controlled/living radical polymerization with a novel bifunctional initiator, 4‐(2‐bromopropanoyloxy)‐N‐(p‐methylbenzyloxy)‐2,2,6,6‐tetramethylpiperidine. The initiator was synthesized in a facile manner using commercially available p‐xylene and 4‐hydroxy‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl (4‐hydroxy TEMPO). Through stepwise atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) and nitroxide‐mediated radical polymerization (NMRP) of 4‐vinylpyridine (4VP), the PMMA‐b‐P4VP copolymer was prepared with a wide range of the copolymer compositions. Microphase‐separation was demonstrated in cross sectional TEM images of self‐standing block copolymer membranes.
The miscibility of CA/P(VP‐co‐MMA) blends was examined as a function of DS of CA and the VP fraction in the copolymer composition, in an extension of the previous studies on cellulose ester blends using P(VP‐co‐VAc) as a counter component. It was observed by DSC thermal analysis that when CA of DS ≤ 2.5 and P(VP‐co‐MMA) of VP > 30 mol‐% were two blending components, most of the binary polymer systems were miscible, whereas the other combinations of DS and VP values led to an immiscible series of blends, a possible exception being the miscible pair of DS = 2.70 and VP = 100 mol‐%. Results of FT‐IR and solid‐state 13C CP/MAS NMR spectra measurements suggested the miscibility to be driven by the hydrogen‐bonding interaction between the residual hydroxyls of CA and the carbonyls of VP units in P(VP‐co‐MMA), as in the case of CA/P(VP‐co‐VAc) blends where the range of miscible pairing of acetyl DS and VP fraction was rather wide. From evaluations of proton spin‐lattice relaxation times in the NMR study, it was confirmed that the homogeneity of the miscible blends of CA/P(VP‐co‐MMA) was substantially on a scale within a few nanometers. To interpret the difference in the DS‐ and copolymer composition‐dependence of the miscibility behavior between three blend systems, CA/P(VP‐co‐MMA), CA/P(VP‐co‐VAc), and CB/P(VP‐co‐VAc), Krigbaum‐Wall intermolecular interaction parameters were estimated by solution viscometry for different polymer pairs pertinent to those blends. In particular, discussion took into consideration the effectiveness of an intramolecular repulsive action between the two units (VP and VAc, or VP and MMA) constituting the vinyl copolymers.
We present an analysis of the temperature‐dependent dynamic behavior of the minority phase of photoaddressable block copolymers. Solid‐state 2H NMR investigations are compared with holographic experiments. The samples are diblock copolymers based on polystyrene (PS) and poly(1,2‐butadiene) (PB), where the PB minority segment is functionalized with different deuterated moieties. Solid‐state 2H NMR investigations were performed from 320 to 380 K in order to study the thermal behavior of the minority segment. Holographic experiments on thin films of the block copolymers yielded the photoinduced diffraction efficiency at different temperatures. The comparison of both datasets enables us to identify the glass transition temperature Tg of the minority phase.
Copolymerizations of tetrafluoroethylene (TFE) and perfluoro(3,6‐dioxa‐4‐methyl‐7‐octen)sulfonyl fluoride (PSVE) initiated by bis(perfluoro‐2‐n‐propoxypropionyl) peroxide in supercritical carbon dioxide are investigated. The reactivity ratios for TFE (rTFE) and PSVE (rPSVE) are calculated to be 7.85, 0.079 and 7.92, 0.087 according to Fineman–Ross and Kelen–Tudos methods, respectively. The glass transition temperatures of the copolymers increase with increasing in PSVE content. Comparison studies on above copolymers and another fluorinated sample prepared in emulsion show that the copolymers have comparable properties to the fluorinated one, thus offering an economic way to improve the properties of TFE–PSVE copolymers for their applications in diverse fields.
