Synthesis of Poly(ϵ‐caprolactone‐co‐methacrylic acid) Copolymer via Phosphazene‐Catalyzed Hybrid Copolymerization

Poly(?‐caprolactone‐co‐tert‐butyl methacrylate) (CL‐co‐BMA) random copolymer is synthesized via hybrid copolymerization with 1‐tert‐butyl‐4,4,4‐tris(dimethylamino)‐2,2‐bis[tris(dimethylamino)phophoranylidenamino]‐2Λ5,4Λ5‐catenadi(phosphazene) (t‐BuP₄) as the catalyst. The copolymer is hydrolyzed into poly(?‐caprolactone‐co‐methacrylic acid) (CL‐co‐MAA), a charged copolymer. Nuclear magnetic resonance, Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis measurements indicate that cyclic ester and vinyl monomer form a random copolymer. The degradation of the copolymers has also been studied by use of quartz crystal microbalance with dissipation.     

Crystallization of Poly(vinylidene fluoride) in Blends with Poly(methyl methacrylate‐co‐methacrylic acid) Copolymers

A series of poly(methyl methacrylate‐co‐methacrylic acid) (PMMA‐co‐MAA) random copolymers ranging in MAA content from 0–15 mol% is synthesized and blended with poly(vinylidene fluoride) (PVDF). Using infrared spectroscopy, it is observed that the absorption bands attributed to hydrogen‐bonded carbonyl groups increase in intensity as the amount of MAA in the copolymer increases. In DSC analysis, the crystallization temperature of the PVDF in the blend initially decreases by ca. 12 °C with MAA contents ranging from 0 to 5.5 mol%; however, a PVDF blend with a 15 mol% MAA copolymer has a crystallization temperature that is only ca. 3 °C below that of pure PVDF. Similarly, spherulitic growth rate analysis initially shows a decrease in radial growth rate for PVDF in blends with PMMA‐co‐MAA copolymers containing less than 5.5 mol% MAA. At higher MAA copolymer contents, the spherulitic growth rate approaches that of pure PVDF. It is concluded that the presence of the MAA comono­mer in the PMMA‐co‐MAA copolymer initially (<5.5 mol% MAA) increases the intermolecular interactions between the copoly­mer and the PVDF. However, as the MAA content of the copolymer rises above 5.5 mol%, intramolecular hydrogen bonding interactions within the PMMA‐co‐MAA copolymer cause the copoly­mer to be less compatible with PVDF.

     

High‐pressure free‐radical copolymerization of ethene with methacrylic acid and ethene with acrylic acid, 2. Ethene reactivity ratios

Free‐radical copolymerizations of ethene (E) with methacrylic acid (MAA) and of E with acrylic acid (AA) were carried out in a continuously operated tank reactor at 2000 bar and temperatures up to 280°C. The (M)AA content of the polymer, F_(M)AA, that may be reached by polymerization in homogeneous phase, e. g., at 260°C, is below 10 mol‐% and the associated (M)AA content of the monomer mixture is below 1 mol‐%. Under such conditions, the ethene and the comonomer reactivity ratios, r_E and r_(M)AA, respectively, can not be simultaneously derived by fitting the measured F_(M)AA and f_(M)AA data according to the classical procedure. With r_(M)AA, however, being available from a preceding ¹³C NMR study¹⁾, r_E may be calculated from each pair of experimental F_(M)AA and f_(M)AA values. F_(M)AA values are determined by means of elemental analysis of carbon and oxygen with consistency checks of copolymer composition being performed via FT‐IR spectroscopy on polymeric films. f_(M)AA is deduced from the measured monomer feed fluxes and from the amount and composition of the copolymer produced within given intervals of stationary polymerization. The r_E data for the E/MAA and E/AA systems are presented and discussed. At identical polymerization pressure and temperature, the measured r_E values of both systems agree within about ± 10%. The r_E values, in addition, are very close to the ethene reactivity ratios that were recently measured for several E/(meth)acrylate copolymerizations. Arguments for this family‐type behavior of r_E are discussed.     

Water‐Swollen Hydrogels with Pendant Terthiophenes

A chemically cross‐linked and water‐swollen poly(AA3T‐co‐AA) gel having pendant terthiophenes was synthesized by radical copolymerization of [(2,2′:5′,2″‐terthiophen‐5‐yl‐)methyl acrylate] (AA3T) and acrylic acid (AA), and its swelling, dissociation, and doping behaviors were studied. The gel swells in high pH solution, which is associated with the dissociation and, hence, electrostatic repulsion of the AA units, and the pH value at which the swelling starts increases with increasing AA3T composition. The dissociation of the gels is suppressed, presumably due to the incorporation of the hydrophobic AA3T unit, and, once started, the dissociation could be promoted by AA3T in the low pH region. Poly(AA3T‐co‐AA) copolymers and gels can be easily electrochemically and chemically doped. The volume change of the gels is observed during doping/undoping and the maximum volume change reached was about 50%.

The pH dependence of the degree of swelling, q, for poly(AA3T‐co‐AA) gels with various F at 25 °C. (?) F = 0.11, DCL = 20%; (?) F = 0.05, DCL = 20%; (?) F = 0, DCL = 10%.     

Crystalline Structure and Thermal Behavior of Water‐Soluble Copolymers with Pendant Terthiophenes

The water‐soluble copolymers having pendant terthiophene, poly(AA3T‐co‐AA), were synthesized by radical copolymerization of [(2,2′ : 5′,2′′‐terthiophen‐5‐yl)methyl acrylate] (AA3T) and acrylic acid (AA), and their molecular structures and thermal behaviors were studied. X‐ray diffraction study showed that the copolymers containing a certain amount of AA3T can form the crystals with monolayer structure, while incorporation of too many AA units into the copolymers disrupted this structure. Possible mechanism of self‐doping on heating was discussed in terms of interaction between AA3T unit with AA unit in the copolymers.     

Copolymers from tert‐Butyl Methacrylate with Trimethylsilyl Methacrylate or Methacrylic Acid: Models for Resist Polymers

Free radical copolymerisation of tert‐butyl methacrylate ( 1 ) with trimethylsilyl methacrylate ( 2 ) and methacrylic acid ( 3 ) has been investigated. Reactivity ratios for methacrylic acid and tert‐butyl methacrylate indicate an azeotropic copolymerisation (r ₁ = 0.476 ± 0.103; r ₃ = 0.300 ± 0.032), whereas the two esters show preferential incorporation of 2 (r ₁ = 0.170 ± 0.050; r ₂ = 1.170 ± 0.124). Thermal cis‐elimination of isobutylene from the tert‐butyl ester and subsequent formation of six‐membered cyclic anhydride moieties has been studied. For poly(methacrylic acid‐co‐tert‐butyl methacrylate) thermogravimetry could be used to determine copolymer composition. Solvolytic desilylation of the trimethylsilyl ester groups has been investigated as an alternative route to poly(methacrylic acid‐co‐tert‐butyl methacrylate). The tert‐butyl ester is not affected under the conditions of desilylation. Sequence distribution of both copolymers has been calculated using the method introduced by Bruns and Motoc.

Copolymer composition diagram for tert‐butyl methacrylate/methacrylic acid.     

Etude diélectrique de deux copolymères du méthylcyanure de vinylidène avec le 4‐fluorostyrène et le 4‐chlorostyrène

The dielectric properties of 2 copolymers poly[(methyl vinylidene cyanide)‐co‐(4‐chlorostyrene)] and poly[(methyl vinylidene)‐co‐(4‐fluorostyrene)] have been studied. These products are chiefly alternating and have relatively high glass transition temperatures, respectively at 145°C and 160°C. α relaxation phenomena have been characterised around to these temperatures. The values of dielectrical increment Δε have been calculated and compared to those of similar copolymers synthesized from vinylidene cyanide with various substituted styrenes. The low values are due to the steric effect of the bulky aromatic cycles. The orientation abilities of CN dipoles decrease comparatively to that of the copolymer of vinylidene cyanide with vinylacetate and this could explain the low piezo or pyroelectric properties.     

Synthesis,Characterization and In Vitro Cytotoxicity of Poly[(5‐benzyloxy‐trimethylene carbonate)‐co‐(trimethylene carbonate)]

The ring‐opening copolymerization of 5‐benzyloxy‐trimethylene carbonate (BTMC) with trimethylene carbonate (TMC) was described. The polymerization was carried out in bulk at 150°C using stannous octanoate as initiator. The influence of reaction conditions such as polymerization time and initiator concentration on the yield and molecular weight of the copolymers were investigated. The poly(BTMC‐co‐TMC)s obtained were characterized by FT‐IR, ¹H NMR, ¹³C NMR, GPC and DSC. NMR results of copolymer showed no evidence for decarboxylation occurring during the propagation. The relationship between the copolymer glass transition temperature and composition was in agreement with the Fox equation. The in vitro cytotoxicity studies of the poly(BTMC‐co‐TMC) (50 : 50) using 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assay demonstrated that the copolymer has low cytotoxicity compared to poly[(lactic acid)‐co‐(glycolic acid)] (75 : 25).     

Long‐chain and short‐chain branches in ethene‐methyl acrylate copolymers studied by quantitative 13C NMR spectroscopy

The frequency of long‐chain branches (LCBs) in ethene (E)‐methyl acrylate (MA) copolymers is investigated for material that was synthesized at 150°C and 2 000 bar at different levels of conversion but constant copolymer composition. The copolymers exhibit significantly more LCBs than found in LDPE synthesized under similar conditions. Moreover, it is found that the LCB frequency increases with conversion. At 0.3 mol‐% conversion 0.3 LCBs and at 4.0 mol‐% conversion 1.1 LCBs per 1 000 C atoms are observed. In addition, the frequency of short‐chain branches (SCBs) in the copolymers is investigated. About 9 mol‐% of the acrylate units are alkylated, which corresponds to numbers given in literature. As sensors, both LCB and SCB indices provide valuable information for simulation calculations to determine rate coefficients for inter‐ and intramolecular transfer reactions.     

Temperature and pH dependence of the catalytic activity of colloidal platinum nanoparticles stabilized by poly[(vinylamine)‐co‐(N‐vinylisobutyramide)

Colloidal platinum nanoparticles in the size range of 5–35 Å have been successfully prepared in water at room temperature by NaBH₄ reduction of ionic platinum in the presence of poly[(vinylamine)‐co‐(N‐vinylisobutyramide)] (PVAm‐co‐PNVIBA). To our knowledge, the temperature‐ and pH‐responsive copolymer was used for the first time as the stabilizer of colloidal metal particles. Three PVAm‐co‐PNVIBA copolymers with PVAm contents of 4.1, 8.3, and 19.8 mol‐% were examined. The particle size and morphology of the platinum colloids varied with the copolymer composition, as confirmed by TEM measurements. The polymer‐stabilized Pt nanoparticles precipitated on heating above their critical flocculation temperatures (CFTs), which were strongly dependent on the solution pH and the copolymer composition. The CFTs were 0.2–1.6°C lower than the lower critical solution temperatures (LCSTs) of the copolymers free in water and the differences increased with increasing PVAm content. The catalytic activity of the Pt nanoparticles was investigated in the aqueous hydrogenation of allyl alcohol. It was found that the activity was regulated through temperature‐ and pH‐induced phase separation. The PVAm content also strongly effected the catalytic activity and the morphology of phase separated catalysts. With a PVAm content of 4.1 mol‐%, the colloidal platinum sol reversibly changed its catalytic activity with changes in temperature.     

Effect of the Acrylic acid Content on Miscibility and Mechanical Properties of Mixtures of Poly[ethylene‐co‐(acrylic acid)] and Poly(2‐ethyl‐2‐oxazoline)

The miscibility behavior of blends of poly(2‐ethyl‐2‐oxazoline) (PEOX) and poly[ethylene‐co‐(acrylic acid)] was studied as a function of the acrylic acid content with the help of differential scanning calorimetry (DSC), modulated DSC and dynamic mechanical thermal analysis (DMTA). Miscibility, ascertained by the existence of a single glass transition in the mixtures, is achieved only between the PEOX and the copolymers with a high acrylic acid content (20%). The other two polymer pairs are immiscible at all compositions. FTIR spectroscopy demonstrates that miscibility is enhanced by hydrogen bonding interactions between the amide groups of the PEOX and the carboxylic groups of the acrylic acid units in the copolymer. Tensile stress and compressive creep tests reveal that the 20 and the 40 wt.‐% PEOX blends exhibit synergistic mechanical properties, i. e., better ultimate properties, smaller Young's moduli and higher creep compliances.     

Water Transport Properties of pH‐Responsive Hydrogels Based on Poly(methacrylic acid) with Polyether Side Chains by Magnetic Resonance Imaging

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.

     

Dielectric Study of the Effect of a Sol‐Gel Inorganic Network on Polymeric Relaxation Dynamics in Acrylic/Titania Hybrids

Summary: In this research, poly[(methyl methacrylate)‐co‐(butyl methacrylate)‐co‐(methacrylic acid)]/TiO₂ hybrids were prepared by the sol‐gel process. The copolymer composition was 16 mol‐% methyl methacrylate (MMA), 80 mol‐% butyl methacrylate (BMA) and 4 mol‐% methacrylic acid (MA). The dielectric properties of the hybrids with varying titania content were measured over the frequency range 0.1 Hz to 100 kHz and between 25 and 160 °C. In addition, the hybrids were investigated using differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). In the given frequency range, a single relaxation peak was observed both by dielectric relaxation spectroscopy (DRS) and DMTA. The single relaxation observed by DRS behaves in the manner of an α‐relaxation, with the frequency–temperature locus showing non‐Arrhenius behavior (curved downwards like a VTF law). The change in the DRS and DMTA characteristics in hybrids compared to the pure polymer reflect the presence of antagonistic mechanisms controlling the dynamics of the polymer chains: nanodomains with enhanced and restricted mobilities are suggested to be responsible for the broadening of the isochronal dielectric loss curve toward, respectively, the low and the high temperature sides. Combining the DSC and DRS results, it can be inferred that the domains with enhanced mobility result from internal and external plasticization effects that reduce the intermolecular hydrogen bonds between the polymer chains. Besides, the motion of polymer chains is found to be significantly hindered by the titania network, due to the presence of iono‐covalent bonds between the polymer and titania and geometrical restrictions in high junction‐point density and titania‐rich microphases. From the Arrhenius plot, it is also shown that the addition of sol‐gel titania more severely hinders the segmental motion of the macromolecular chains than the local motion of the lateral groups (β relaxation).

Simplified schematic morphology for the poly(MMA‐co‐BMA‐co‐MA)/TiO₂ hybrids.     

Synthesis and Self‐Assembly of o‐Nitrobenzyl‐Based Amphiphilic Hybrid Polymer with Light and pH Dual Response

In this paper, novel light‐responsive polyhedral oligomeric silsesquioxane (POSS) end‐capped poly(o‐nitrobenzyl methacrylate) (POSS–PNBMA) are synthesized by the combination of atom transfer radical polymerization (ATRP) and click chemistry. After subsequent partial photocleavage of PNBMA yielding poly(methacrylic acid) (PMAA), pH‐ and light‐responsive random copolymer of POSS–P(NBMA‐co‐MAA) is obtained. The o‐nitrobenzyl‐based amphiphilic hybrid polymer can self‐assemble into spherical micelles in aqueous solution. Hydrophobic POSS and PNBMA segments aggregate into the inner core, and the hydrophilic PMAA chains tend to stretch from the core. The micellar morphology can be tuned by pH changes and UV irradiation. Light irradiation leads to the transformation of P(NBMA‐co‐MAA) into PMAA and to the reorganization of the assemblies, causing the release of encapsulated guest molecule Nile Red into water. This dual‐responsive polymer has a broad potential use in targeted drug delivery.

     

Synthesis of Amphiphilic Poly(ethylene oxide‐co‐glycidol)‐graft‐polyacrylonitrile Brush Copolymers and their Self‐assembly in Aqueous Media

An amphiphilic copolymer brush poly(ethylene oxide‐co‐glycidol)‐graft‐polyacrylonitrile [poly(EO‐co‐Gly)‐g‐PAN], is successfully prepared for the first time by a combination of anionic polymerization and redox free radical polymerization. The final products and intermediates are characterized by NMR and GPC. Aggregates made from the brush copolymers, poly(EO‐co‐Gly)‐g‐PAN, with a long hydrophobic graft length in water are studied by TEM and DLS. The effects of hydrophobic graft length and water content on the morphologies are discussed. Some rare morphologies of aggregates are observed, such as lamellae, bicontinuous networks, bowls or nanosheets, and large compound rods with a brittleness that can be ascribed to the orientation of high content semi‐crystalline PAN segments.     

One‐Step Method for Synthesis of PDMS‐Based Macroazoinitiators and Block Copolymers from the Initiators

Summary: This paper presents a facile one‐step method for the synthesis of macroazoinitiator (MAI) by direct polycondensation of hydroxyalkyl‐terminated polydimethylsiloxane (PDMS) with 4,4′‐azobis‐4‐cyanopentanoic acid (ACPA) under mild conditions. The PDMS‐based MAI was characterized by FTIR, ¹H NMR, GPC, and UV spectroscopy, and further used as an initiator for polymerization of methyl methacrylate (MMA) to obtain PMMA‐co‐PDMS block copolymer. TEM observation and DSC analysis demonstrated that the PMMA‐co‐PDMS block copolymer had a microphase‐separated structure.

Schematic representation for syntheses of macroazoinitiators (MAI) by the direct polycondensation and corresponding block copolymers.     

Spontaneous Self‐Assembly and Micellization of Random Copolymers in Organic Solvents

Spontaneous self‐assembly of random and statistical copolymers in solution, especially in organic solvents, is unusual due to the structural irregularity of the copolymer chain and close proximity of short incompatible segments. This study describes the first observation of supramolecular structures such as micelles and vesicles formed by a random copolymer in organic solvents. Upon dissolution in methanol or tetrahydrofuran, the random copolymer poly(trifluoroethyl methacrylate‐random‐methacrylic acid) forms small spherical micelles, worm‐like assemblies, and large vesicles spontaneously. Self‐assembly is driven by the high incompatibility between the fluorinated and acidic repeat units. Micelle size can also be altered by the addition of metal ions, which interact with the carboxylic acid groups of methacrylic acid through complexation or Coulombic forces. These findings demonstrate an easy, single‐step approach to creating nanoscale structures with tunable size and morphologies in organic solvents from easily synthesized random copolymers, with potential applications in coatings, selective membranes, catalysis, and drug delivery.     

Synthesis and characterization of dextran grafted with poly(N‐isopropylacrylamide‐co‐N,N‐dimethyl‐acrylamide)

Graft copolymers consisting of dextran as a main chain and poly(N‐isopropylacrylamide‐co‐N,N‐dimethylacrylamide) (poly(NIPAAm‐co‐DMAAm)) as graft chains were synthesized. For the synthesis of the graft copolymers, a semitelechelic poly(NIPAAm‐co‐DMAAm) with an amino end‐group was obtained by radical copolymerization with ethanethiol as a chain transfer agent, followed by a coupling reaction of its hydroxyl end‐group with ethylenediamine. Graft copolymers with various length of the grafts were obtained from coupling reactions between carboxymethyl dextran and poly‐(NIPAAm‐co‐DMAAm) in the presence of a water‐soluble carbodiimide. The graft copolymers in phosphate buffer exhibit lower critical solution temperatures due to thermosensitivity of their grafts. There is no significant change in the hydration‐dehydration behavior of the poly(NIPAAm‐co‐DMAAm) chain after the grafting reaction. The existence of such grafts in dextran may play an important role for modulated degradation in synchronization with temperature.     

NMR Studies of the Structure and Dynamics of Polymer Gels Based on N‐Isopropylacrylamide (NiPAAm) and Methacrylic Acid (MAA)

A series of copolymer gels and interpenetrating networks (IPN) based on N‐isopropylacrylamide (NiPAAm) and methacrylic acid (MAA) were synthesized and subsequently investigated by magic angle spinning ¹H MAS, cross polarization ¹³C CP‐MAS and pulse‐saturation transfer ¹³C PST‐MAS NMR. The structure of the interpenetrating networks is compared to that of the copolymer gels with the same composition. The study of the proton lines reveals low mobility of the chains in the copolymer gels and IPN with higher concentration of MAA, whereas those which are predominantly N iPAAm show higher mobility and therefore narrower proton lines. ¹³C CP‐MAS revealed an interaction between the components of the IPNs. The PST‐MAS technique was utilized to study the structure of the polymers in the gel phase. Copolymer gels exhibit some additional peaks in the carbonyl region due to the new chemical environment in the stereoregular sequences. In order to assure assignment, uncrosslinked copolymers with similar compositions as the copolymer gels were synthesized for comparative purposes and examined by conventional solution‐state ¹³C NMR. A linear homopolymer of N iPAAm was synthesized inside of a P(MAA) gel. The polymer was extracted after the completion of the reaction and characterized by solution ¹³C NMR. About 24% of this P(N iPAAm) homopolymer could not be extracted presumably because of a strong hydrogen bonding or partial topological constrains. In the ¹³C NMR spectrum a new signal appeared in the carbonyl region due to MAA monomeric units. It may correspond to the methacrylic carbonyls interacting by hydrogen bonds with the amide groups.     

Adhesion of cultured human endothelial cells onto methacrylate polymers with varying surface wettability and charge

The adhesion of human endothelial cells (HEC) onto a series of well-characterized methacrylate polymer surfaces with varying wettabilities and surface charges was studied either in serum-containing (CMS) or in serum-free (CM) culture medium. HEC adhesion in CMS onto (co)polymers of hydroxyethyl methacrylate (HEMA) and methyl methacrylate (MMA) was found to be optimal on the moderately wettable copolymer (mol ratio 25 HEMA/75 MMA). Positively-charged copolymers of HEMA or MMA with trimethylaminoethyl methacrylate-HCl salt (TMAEMA-Cl), both with mol ratios of 85/15 and a negatively-charged copolymer of MMA with methacrylic acid (MAA), mol ratio 85/15, showed high numbers of adhering HEC. In CM, HEC adhered onto the three charged copolymers mentioned above, but neither onto the copolymer of HEMA and MAA (mol ratio 85/15) nor onto the HEMA/MMA co- and homopolymers. Complete cell spreading in CM was only observed on the positively-charged copolymers.