Photocrosslinking of poly(2,3-epithiopropyl methacrylate) film with 254 nm irradiation

Poly(2,3-epithiopropyl methacrylate) (PETMA) has an absorption maximum at 258 nm (ε_max = 50) in dioxane which is due to episulfide groups. When irradiated at 254 nm under atmospheric pressure its film became insoluble. When kept at 70°C for several minutes a PETMA film became partially insoluble; however, the contribution of this thermal reaction to the photocrosslinking at room temperature was negligible. For photoreaction at 254 nm under nitrogen a low probability of main-chain scission was ascertained by the use of the Charlesby-Pinner equation. The IR spectrum of irradiated PETMA showed a decrease in episulfide groups and the formation of mercapto groups, which suggested that the photocrosslinking of PETMA results from free radicals formed by the cleavage of C? S bonds. Free radicals in the irradiated PETMA were detected by ESR spectroscopy and the assignment is discussed. In this photocrosslinking process oxygen was a retarder at the early stage but an accelerator at the later stage.     

Photocrosslinking of poly(2,3-epithiopropyl methacrylate) by the oxidation of pendant episulfide groups

In the photocrosslinking of poly(2,3-epithiopropyl methacrylate) (PETMA) films the effect of the pendant episulfide group's oxidation on the crosslinking of PETMA was investigated. Thermal crosslinking of PETMA is promoted by peroxides such as benzoyl peroxide and hydrogen peroxide. IR spectrum of the crosslinked PETMA showed that the reaction proceeded through the oxidation of episulfide groups by the peroxides. The anthracene (An) sensitized photocrosslinking of PETMA films also proceeded via the oxidation of episulfide groups by singlet oxygen. It was found that residual tetrahydrofuran (THF) in the films remarkably increased the rate of the photocrosslinking and/or reduced the induction period. From the further investigation concerning casting solvents it was found that residual CS₂, CCl₄, and CHCl₃ in films increased the rate of the photocrosslinking and/or reduced the induction period of the photocrosslinking. The disappearance rate of An in the films was also increased by the presence of residual CS₂, CCl₄, and CHCl₃, differring from the result of THF. These results were explained by a difference in lifetime of singlet oxygen in the films. From the results were explained by a difference in lifetime of singlet oxygen in the films. From the results concerning the effects of hydroperoxides such as THF hydroperoxide and t-butyl hydroperoxide on the photocrosslinking of PETMA films the acceleration effect of the residual THF was deduced to be due to the promotion of singlet oxygen-oxidation of sulfide groups by protic compounds such as THF hydroperoxide and H₂O in the THF.     

Photocationic crosslinking of poly(2,3-epithiopropyl methacrylate) and photo-initiated cationic polymerization of its model compounds

Photocationic crosslinking of a poly(2,3-epithiopropyl methacrylate) (PETMA) film containing 4-N,N-diethylaminobenzene diazonium tetrafluoroborate (DAC) was investigated. Very rapid photocrosslinking of PETMA was observed and the rate was greater than that of poly(glycidyl methacrylate) with DAC. Post-heating of the irradiated PETMA film resulted in a decrease of the insoluble fraction. This decrease was explained by scission of crosslinking points by the BF₃. In the present conditions, more than 0.3 wt % of DAC was required to insolubilize the PETMA film. Photopolymerizations of propylene sulfide (PS) and 2,3-epithiopropyl pivalate (ETPP) in the presence of DAC were investigated. The polymerization of PS proceeded smoothly but addition of ethyl acetate to PS depressed the rate and the degree of polymerization. ETPP could not be polymerized but copolymerized with PS by this method. Addition of ETPP to PS depressed both the rate of the polymerization and the degree of polymerization. From these results, it is deduced that the photocrosslinking of a PETMA film is caused by a cationic polymerization of episulfide groups but the chain length is not large.     

Electrospinning of the hydrophilic poly (2-hydroxyethyl methacrylate) and its copolymers with 2-ethoxyethyl methacrylate

The goal was to electrospin 2-hydroxyethyl methacrylate — based biocompatible polymers and prepare submicron fibres (nanofibers) for biomedicinal applications. Syntheses of poly(2-hydroxyethyl methacrylate) (HEMA) and its copolymer with 2-ethoxyethyl methacrylate (EOEMA), and their characterization by viscometry and molecular weight are described. Their relation to electrospinning is discussed. Electrospinning of HEMA homopolymer from water-ethanol is successful for molecular weights 6.31 × 10⁵ and 1.80 × 10⁶ g/mol. Electrospinning of HEMA/EOEMA copolymers is feasible from ethanol.      

A novel route to poly(2-hydroxyethyl methacrylate) and its amphiphilic block copolymers

The vinyl of the ester group of 2-vinyloxyethyl methacrylate was first selectively reacted with acetic acid to obtain 2-[1-(acetoxy)ethoxy]ethyl methacrylate ( 2 ). This protected monomer was subjected to anionic polymerization in tetrahydrofuran at −60°C in the presence of LiCl, using 1,1-diphenylhexyllithium as initiator. The molecular weight of the polymer could thus be controlled and a narrow molecular weight distribution obtained. The protecting group, 1-(acetoxy)ethyl, could be easily eliminated (by quenching the polymerization reaction with methanol and water) to generate poly(2-hydroxyethyl methacrylate) (poly(HEMA)). Block copolymers were also prepared by the sequential anionic polymerization of MMA and 2 or styrene and 2 . They possess narrow molecular weight distributions, and controlled molecular weights and compositions. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1865–1872, 1998     

Blends of glycidyl methacrylate/methyl methacrylate copolymers with poly(vinylidene fluoride)

Blends of glycidyl methacrylate (GMA)/methyl methacrylate (MMA) copolymers with poly (vinylidene fluoride) (PVDF) were found to be miscible when the GMA content of the copolymer is 35.7 wt % or less. The miscible blends did not phase separate upon heating prior to thermal decomposition. The melting point depression method, based on both the Flory-Huggins theory and the equation of state theory of Sanchez-Lacombe, was used to evaluate interaction parameters for each pair. The magnitude of these parameters appears to be much larger than interaction energies evaluated by other methods. Possible reasons for this are discussed. © 1995 John Wiley & Sons, Inc.     

Synthesis of block copolymers containing poly(ferrocenylmethyl methacrylate) units

Ferrocenylmethyl methacrylate (FMMA) has been polymerized by using LiAlH₄–tetramethyl-ethylenediamine initiation to form living polymers in high vacuum systems. The addition of methyl methacrylate or acrylonitrile to these living systems gave the block copolymers FMMA-block MMA and FMMA-block AN. The anions were not nucleophilic enough to initiate styrene polymerization. Therefore, living polystyrene was prepared (sodium naphthalide initiation in THF at ?78°C) and upon FMMA addition, styrene-block FMMA copolymers were formed. Extraction, precipitation, and gel-permeation chromatography studies were performed to examine the purity of the block copolymers.     

Block copolymers of thiophene-capped poly(methyl methacrylate) with pyrrole

Poly(methyl methacrylate) with a thiophene end group having narrow polydispersity was prepared by the Atom Transfer Radical Polymerization (ATRP) technique. Subsequently, electrically conducting block copolymers of thiophene-capped poly(methyl methacrylate) with pyrrole were synthesized by using p-toluene sulfonic acid and sodium dodecyl sulfate as the supporting electrolytes via constant potential electrolysis. Characterization of the block copolymers were performed by CV, FTIR, SEM, TGA, and DSC analyses. Electrical conductivities were evaluated by the four-probe technique. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4218–4225, 1999     

Thermal degradation of poly(vinyl bromide), vinyl bromide-methyl methacrylate copolymers,and poly(vinyl bromide)-poly(methyl methacrylate) blends

Degradation behavior has been compared for PVB, five VB-MMA copolymers which span the composition range, PMMA, and PVC by using thermogravimetry in dynamic nitrogen and thermal volatilization analysis (TVA) under vacuum for programmed heating at 10°C/min. Volatile products have been separated by subambient TVA and identified. PVB is substantially less stable than PVC but shows inmost respects analogous degradation behavior. The introduction of VB into the PMMA chain leads to intramolecular lactonization with release of methyl bromide at temperatures a little above 100°C; after this reaction is complete, however, the polymer is more stable toward volatilization than PMMA. Copolymers with moderate and high VB contents also lose hydrogen bromide. Carbon dioxide is a significant product at intermediate compositions. The variation of product distribution with copolymer composition is discussed in relation to the several reactions involved and comparisons are made with VC-MMA copolymers. PVB-PMMA blends snow some features of degradation behavior in common with the PVC-PMMA system but also very important differences. The effect of PVB is only to stabilize the PMMA; the mechanism is discussed. The role of PVB as an additive and VB as a comonomer for fire-retardant PMMA compositions is briefly considered in relation to earlier studies.     

Methyl methacrylate oligomerically-modified clay and its poly(methyl methacrylate) nanocomposites

A methyl methacrylate oligomerically-modified clay was used to prepare poly(methyl methacrylate) clay nanocomposites by melt blending and the effect of the clay loading level on the modified clay and corresponding nanocomposite was studied. These nanocomposites were characterized by X-ray diffraction, transmission electron microscopy, thermogravimetric analysis and cone calorimetry. The results show a mixed intercalated/delaminated morphology with good nanodispersion. The compatibility between the methylacrylate-subsituted clay and poly(methyl methacrylate) (PMMA) are greatly improved compared to other oligomerically-modified clays.     

Monolayer properties of mixtures of poly(n-stearyl methacrylate), poly(n-lauryl methacrylate), and their corresponding copolymers

The monolayer properties of poly(n-stearyl methacrylate), poly(n-lauryl methacrylate), and their mixtures at various ratios of the two polymers have been studied from the measurements of their surface pressure–area isotherms at air–water interface. The monolayer properties of their mixtures have been compared with those of their corresponding copolymers. The results show that the isotherms of the mixed monolayers have two break points at higher pressures than that of poly(n-lauryl methacrylate). This suggests that the mixtures may form more stable films that consist of separate phases of the two homopolymers, although each phase may contain a small amount of the other. The isotherms of the copolymer monolayers indicate a phase transition from liquid condensed to solid film between 50 segment mole % and 70% poly(n-stearyl methacrylate). The monclayer of these copolymers has properties that differ from those of the corresponding mixtures of two pure homopolymers and is more compatible than the mixtures of pure homopolymers.     

Preparation of poly(hydroxyethyl methacrylate) and poly(hydroxypropyl methacrylate) latices

Hydroxyethyl methacrylate and hydroxypropyl methacrylate (both having extremely high solubilities in water) were polymerized in aqueous medium to obtain the respective polymer latices with a solid content as high as 10 wt.-%. The initial state of the polymerization is in solution rather than in dispersion, and the polymer product is sparingly soluble in the aqueous phase. The polymerization was carefully controlled to avoid forming hydrogel by using an oil soluble initiator and a mixture of sodium dodecyl sulfate and poly(vinyl alcohol). Solubilities of both monomers and polymers in water were also investigated.     

Synthesis and characterization of novel poly(cycloalkyl methacrylate) bearing fused‐ring structure and its copolymers

A new family of cycloaliphatic fused‐ring acrylic polymers based on 8‐hydroxymethyltricyclo[5.2.1.0^2,6]decane (TCD) has been synthesized by free‐radical polymerization. TCD‐methacrylate (TCD‐MA) was synthesized by reacting TCD with methacrylic acid in toluene via transesterification with p‐toluenesulfonic acid as a catalyst. TCDMA was polymerized in toluene with benzoyl peroxide as a free‐radical initiator at 80 °C. Copolymers were synthesized by polymerizing TCDMA with styrene and methyl methacrylate. The composition of the comonomers was varied from 0 to 100%. Homo‐ and copolymers were characterized by Fourier transform infrared (FTIR) and ¹³C NMR spectroscopy. Molecular weight determination by gel permeation chromatography showed that the polymers were obtained in very high molecular weights in the range of M_n > 50,000 and M_w > 80,000 with relatively low polydispersity. The composition analysis of both the copolymer series were determined by ¹H NMR. The thermal properties of the homo‐ and copolymers were studied with differential scanning calorimetry and all the polymers were found to be amorphous. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5617–5626, 2004     

Thermoresponsive copolymers of methacrylic acid and poly(ethylene glycol) methyl ether methacrylate

Copolymers of methacrylic acid (MAA) and poly(ethylene glycol) methyl ether methacrylate (PEGMA) were prepared and their cloud points in aqueous solution were studied as a function of comonomer ratio, solution pH, and presence of hydrophobic comonomers. Under acidic conditions, the cloud point falls below 0 °C for copolymers with between 25% to 60% ether content, because of the formation of hydrophobic H‐bonded ether–acid complexes. The cloud point also decreases with solution pH. For equivalent ether to acid ratios, the cloud point decreases with decreasing PEG chain length, because of the presence of a larger number of hydrophobic methyl and methacrylate groups. Similarly, the cloud point decreases upon incorporation of hydrophobic comonomers such as butyl, lauryl, or glycidyl methacrylates. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6095–6104, 2005     

Surface structures and properties of polystyrene/poly(methyl methacrylate) blends and copolymers

Sum frequency generation (SFG) vibrational spectroscopy has been applied to study the molecular surface structures of polystyrene (PS)/poly(methyl methacrylate) (PMMA) blends and the copolymer between PS and PMMA (PS-co-PMMA) in air, supplemented by atomic force microscopy (AFM) and contact angle goniometer. Both the blend and the copolymer have equal weight amounts of the two components. SFG results show that both components, PS and PMMA, can segregate to the surface of the blend and the copolymer before annealing, although PMMA has a slightly higher surface tension. Upon annealing both SFG results and contact angle measurements indicate that the PS segregates to the surface of the PS/PMMA blend more but no change occurs on the PS-co-PMMA surface. AFM images show that the copolymer surface is flat but the 1:1 PS/PMMA blend has a rougher surface with island like domains present. The annealing effect on the blend surface morphology has also been investigated. We collected amide SFG signals from interfacial fibrinogen molecules at the copolymer or blend/protein solution interfaces as a function of time. Different time-dependent SFG signal changes have been observed, showing that different surfaces of the blend and the copolymer mediate fibrinogen adsorption behavior differently.     

Synthesis and characterization of random copolymers of (2,2-dimethyl-1,3-dioxolan-4-yl)methyl methacrylate and 2,3-dihydroxypropyl methacrylate

Poly[(2,2-dimethyl-1,3-dioxolan-4-yl)methyl methacrylate)] [poly(solketal methacrylate) (PSMA)] was synthesized by free radical polymerization. By partial hydrolysis of the acetal group, random copolymers of SMA with 2,3-dihydroxypropyl methacrylate (DHPMA) were synthesized whereas complete cleavage lead to poly(2,3-dihydroxypropyl methacrylate) (PDHPMA). The copolymer composition was determined by ¹H NMR spectroscopy. FTIR spectroscopy indicates the synthesis of random copolymers with different degrees of hydrogen bonding as measured by a shift of the OH vibration bands. The glass transition temperature of the random copolymers increases linearly with increasing DHPMA content, resulting in a positive deviation from the Fox equation. The thermal degradation of both homopolymers and their random copolymers has been studied. Finally, the solution behaviour of the copolymers and PDHPMA in water studied by dynamic light scattering showed a strong tendency of the polymer chains to form clusters in the size range of 15-62 nm. The size and the kind of associating interactions within the clusters strongly depend on the copolymer composition.