Jun-ichi Ikeda

Preparation and properties of highly phosphorylated poly(vinyl alcohol) hydrogels chemically crosslinked by glutaraldehyde

Abstract New anionic polyelectrolyte gels were prepared by the chemical crosslinking reaction of highly phosphorylated poly(vinyl alcohol) (P-PVA) with glutaraldehyde. The structures of the gels were determined by both i.r. and solid-state 13 C n.m.r. spectroscopy. The various types of polyanionic gels having high- or low-swelling characteristics and different degrees of hardness could be prepared by using the crosslinking reaction under different reaction conditions. The gels with low crosslinking densities showed in the order of 500 g g −1 of the maximum absorbency value. The thermal properties of the chemically crosslinked P-PVA were also investigated.

Free-radical crosslinking polymerization of neopentyl glycol dimethacrylate in the presence of lauryl mercaptan

Neopentyl glycol dimethacrylate was polymerized in bulk in the presence of lauryl mercaptan as a chain transfer agent, the primary chain length being reduced to a comparable order in allyl polymerization, and the gelation behavior was compared with diallyl terephthalate (DAT) polymerization as a typical example of multiallyl polymerizations. No Trommsdorff effect was observed, even beyond the gel point conversion, in spite of the polymerization of divinyl monomer, as were the cases of the bulk polymerization of multiallyl compounds. The variation of molecular weight distribution curves with conversion was quite similar to DAT polymerization. The deviation of actual gel point from the theoretical one was also similar. Moreover, the swelling ratio of the gel obtained just beyond the gel point was very high. Thus, no substantial difference was observed between allyl and vinyl polymerizations in the case where the primary chain lengths were adjusted to be comparable. In addition, no microgelation occurred up to the gel point.

Emulsion polymerization of lauryl methacrylate and its copolymerization with trimethylolpropane trimethacrylate

The emulsion polymerization of lauryl methacrylate and its copolymerization with trimethylolpropane trimethacrylate (TMPTMA) were investigated. The induction period (IP) for LMA polymerization was observed to be very long as compared to substantially no IP for methyl methacrylate polymerization. The addition of TMPTMA as a crosslinker clearly prolonged IP, owing to the reduced radical entry of oligomeric growing radical having rather hydrophilic and crosslinkable TMPTMA units into the polymer particle surface. Besides, no gelation was observed even above 90% conversion for LMA/TMPTMA(80/20) copolymerization. The initial abrupt increase in the conversion dependencies of weight-average molecular weight results from the compartmentalization of reaction loci and the gel effect.

Effect of hydrogen bonds on intermolecular crosslinking reaction by introduction of carboxyl groups in free-radical crosslinking monomethacrylate/dimethacrylate copolymerizations

The effect of physical interaction through hydrogen bonds on the intermolecular crosslinking reaction leading to the promoted gelation in free-radical crosslinking monovinyl/divinyl copolymerizations was discussed from the standpoint of the control of network formation. The solution copolymerizations of benzyl methacrylate (BzMA) with 2 mol% of 1,6-hexanediol dimethacrylate in t-butylbenzene were conducted in the absence and presence of different amounts of mono(2-methacryloyloxyethyl) succinate (MMOES). Gelation was promoted by the addition of MMOES and the ratio of the actual gel point to the theoretical one became smaller; this would be related to the formation of hydrogen bonds between carboxyl groups introduced into prepolymer and growing polymer radical. As an extension of the above discussion, we treated the effect of hydrogen bonds on the gelation in the crosslinking BzMA/triicosaethylene glycol dimethacrylate copolymerization. The addition of MMOES obviously promoted the gelation. The ratio of the actual gel point to the theoretical one calculated according to Stockmayers equation [J. Chem. Phys. 12 (1944) 125] was obtained as 1.9, very close to unity.

Steric control of gelation in monovinyl-multivinyl polymerization leading to preparation of self-crosslinkable polymer having pendant vinyl groups

Abstract Steric effects of long-chain alkyl groups on a radical vinyl polymerization including a multivinyl monomer is discussed in connection with control of gelation. Three kinds of alkyl methacrylate (RMA) were added to the system of methyl methacrylate with ethylene dimethacrylate (EDMA) in order to examine the steric effect of the long-chain alkyl group of RMA on the gelation. Study of the significance of steric effects on gelation was extended to the copolymerization of lauryl methacrylate (LMA) with several polyethylene glycol dimethacrylates (PEGDMA); gelation depended on the number of oxyethylene units ( n ) of PEGDMA as a crosslinker and no gelation was observed up to n = 4. Finally, LMA-EDMA copolymerization behaviour was examined in detail by changing monomer concentration and the amount of EDMA; the occurrence of intermolecular crosslinking leading to gelation is obviously suppressed by the steric effect of the long-chain alkyl group, providing a new way for the preparation of novel self-crosslinkable polymers having pendant vinyl groups.

Effect of hydrogen bonds on gelation by introduction of carboxyl groups in the free-radical crosslinking copolymerization of butyl methacrylate with 1,6-hexanediol dimethacrylate

The preliminary study of the effect of physical crosslinking on the gelation in monovinyl/divinyl copolymerizations is described. Thus, mono(2-methacryl-oyloxyethyl) succinate was added to the crosslinking copolymerization of butyl methacrylate with 1,6-hexane-diol dimethacrylate and the gelation was explored in terms of the effect of hydrogen bonds formed between carboxyl groups introduced into the primary polymer chain.

Amphiphilic polymethacrylates as crosslinked polymer precursors obtained by free‐radical monomethacrylate/dimethacrylate copolymerizations

As an extension of our work on the elucidation of the mechanism and control of 3-dimensional network formation in the free-radical crosslinking polymerization and copolymerization of multivinyl compounds with the aim to molecularly design vinyl-type network polymers, novel amphiphilic polymers were prepared as crosslinked polymer precursors. Thus, benzyl methacrylate, a nonpolar monomer, was copolymerized radically with 5 mol % of triicosaethylene glycol dimethacrylate [CH2C(CH3)CO(OCH2CH2)23OCOC(CH3)CH2], a polar monomer, in the presence of lauryl mercaptan as a chain transfer agent. The resulting prepolymers (i.e., vinyl-type network-polymer precursors or amphiphilic polymers) were characterized mainly by viscometry using t-butylbenzene (t-BB) and a t-BB/MeOH (80/20) mixture as solvents. The viscosities in the t-BB/MeOH (80/20) mixture were quite high compared with those in t-BB, and completely reversed concentration dependencies were observed in the solvents. These are discussed by considering the difference in conformation and the shrinkage of polar, flexible polyoxyethylene units or the entanglement of nonpolar, rigid primary chains.

ESR spectroscopic pursuit of radical accumulation processes in the proliferous benzyl methacrylate/neopentyl glycol dimethacrylate copolymerizations in the presence of lauryl mercaptan as chain transfer agent

The anomalous popcorn formation in the presence of a large amount of lauryl mercaptan as a chain transfer agent was explored in the free-radical crosslinking copolymerization of benzyl methacrylate with neopentyl glycol dimethacrylate. Thus, the radical accumulation during proliferous polymerization was pursued ESR-spectroscopically and a brief mechanistic discussion is described.

High density collinear holographic data storage system(Conference Presentation)

Collinear holography has been good candidate for a volumetric recording technology of holographic data storage system (HDSS), because of there are not only large storage capacities, high transfer rates, but also the unique configuration, in which the information and reference beams are modulated co-axially by the same spatial light modulator, as a new read/write method for HDSS are very promising. The optical pickup can be designed as small as DVDs, and can be placed on one side of the recording media (disc). In the disc structure, the preformatted reflective layer is used for the focus/tracking servo and reading address information, and a dichroic mirror layer is used for detecting holographic recording information without interfering with the preformatted information. A 2-dimensional digital page data format is used and the shift-multiplexing method is employed to increase recording density. As servo technologies are being introduced to control the objective lens to be maintained precisely to the disc in the recording and reconstructing process, a vibration isolator is no longer necessary. In this paper, we introduced the principle of the collinear holography and its media structure of disc. Some results of experimental and theoretical studies suggest that it is a very effective method. We also discussed some methods to increase the recording density and data transfer rates of collinear holography using phase modulated page data format.

Big Data Storage Solution: Collinear Holographic Data Storage System

In the big data era, the necessity for large capacity, high transfer rates and long-term data storage systems has been increased. But, the main storage media we rely on currently are magnetic technology, like hard disk drives (HDD) and tape, which life times are several years only. They cannot satisfy the demand of prolonged preservation. Optical discs based on the bit-by-bit method, such as CD, DVD and Blu-ray Disc, for storing sound, movies, photos and other digital contents are widely used in our daily life. The long-term life time is one of the properties. The optical disc should be a good candidate of data storage system for big data preservation. However, the recording density limitation of the bit recording method are looming on the horizon.