Poly styrene-block-methyl methacrylate

Poly(acrylates) and (alkyl acrylates). - Structured nanopore films of poly(styrene-block-methyl methacrylate) copolymers have been made with controlled spectral sensitivity, such that each block is sensitive to a specific degradation wavelength. In copolymers of 2,2,2-trifluoroethyl methacrylate with vinyl ethers, the photosensitivity is controlled by the vinyl ether units. Photodegradation occurs at the tertiary positions of the ether units followed by lactone formation and chain scission processes. Furthermore, the fluorinated side chains have been found to inhibit cyclization reactions. 

Brown and White employed this approach to prepare block copolymers of styrene and mcthacrylic acid (6). They were able to hydrolyze poly(styrene-b-methyl methacrylate) (S-b-MM) with p-toluenesulfonic acid (TsOH). Allen, et al., have recently reported acidic hydrolysis of poly(styrene-b-t-butyl methacrylate) (S-b-tBM) (7-10). These same workers have also prepared potassium methacrylate blocks directly by treating blocks of alkyl methacrylates with potassium superoxide (7-10). 

Preparation of Block Copolymers. Poly(styrene-b-methyl methacrylate) and poly(styrene-b-t-butyl methacrylate) were prepared by procedures similar to those reported for poly(styrene-b-methyl methacrylate (12,13). Poly(methyl methacrylate-b-t-butyl methacrylate) was synthesized by adaptation of the method published (14) for syndiotactic poly(methyl methacrylate) polymerization of methyl methacrylate was initiated with fluorenyllithium, and prior to termination, t-butyl methacrylate was added to give the block copolymer. Pertinent analytical data are as follows. 

Tureau MS, Epps TH (2009) Nanoscale networks in poly[isoprene-block-styrene-block-(methyl methacrylate)] triblock copolymers. Macromol Rapid Commun 30 1751-1755... 

Optical densities at 269.5 nm for polystyrene solutions at concentrations of 0-1 X 10"2 mole/liter and for poly(styrene-co-methyl methacrylate) solutions at a total concentration of 1 X 10 2 mole/liter are presented in Figure 1 as functions of styrene content. The solvents were (from the top) dioxane, chloroform, tetrahydrofuran (THF), tetrachloroethane (TCE), and dichloro-ethane (DCE). It is evident that the linear relationship between optical density and styrene concentration that is valid for a polystyrene at all concentrations (open circles) does not hold for the statistical copolymers (solid circles). For example, copolymer (25-80 mole % styrene) solutions in chloroform deviate markedly from linearity the maximum per cent decrease in extinction coefficient (hypochromism) corresponds to a copolymer containing 50 mole % styrene. We define hypochromism as the decrease in absorption intensity at 269.5 nm per chromophore of the statistical copolymer relative to that of the atactic polystyrene. It is also evident from Figure 1 that the alternating copolymer also gives a sharp hypochromism whereas block copolymers and mechanical mixtures of polystyrene and poly (methyl methacrylate) do not deviate from the straight line. Similar results were obtained with the other solvents, but the composition range where hypochromism appears depends on the solvent used. 

Effects of addition of a compatibilizing block copolymer, poly(styrene-b-methyl methacrylate), P(S-b-MMA) on the rheological behavior of an immiscible blend of PS with SAN were studied by dynamic mechanical spectroscopy [Gleisner et al., 1994]. Upon addition of the compatibilizer, the average diameter of PS particles decreased from d = 400 to 120 nm. The data were analyzed using weighted relaxation-time spectra. A modified emulsion model, originally proposed by Choi and Schowalter [1975], made it possible to correlate the particle size and the interfacial tension coefficient with the compatibilizer concentration. It was reported that the particle size reduction and the reduction of occur at different block-copolymer concentrations. 

The experimental results that will be examined consist of studies that look at the ability of a random copolymer to improve the properties of mixtures of the two homopolymers relative to the ability of a block copolymer. The three different systems that are examined include copolymers of poly(styrene-co-methyl methacrylate) (S/MMA), poly(styrene-co-2-vinyl pyridine) (S/2VP), and poly(styrene-co-ethylene) (S/E) in mixtures of the two homopolymers. The experiments that have been utilized to examine the ability of the copolymer to strengthen a polymer blend include the examination of the tensile properties of the compatibilized blend and the determination of the interfacial strength between the two homopolymers using asymmetric double cantilever beam (ADCB) experiments. 

After these initial considerations, the complete analysis of a number of diblock copolymers of styrene and methyl methacrylate shall be discussed in detail. The poly(styrene-ftlodc-methyl methacrylate)s under investigation were prepared via anionic polymerization of styrene and subsequent polymerization of methyl methacrylate, varying molar mass and composition (B1-B3). The polystyrene precursors (P1-P3) were isolated and characterized separately. As the PMMA block is the more polar block in the block copolymer, a polar (silica gel) column was chosen for establishing the critical point of PMMA. According to case (1) in Fig. 14, the PS block is then eluted in the SEC mode. The behavior of PMMA of different molar masses on silica gel Si-100 in eluents comprising methylethylketone and cyclohexane is shown in Fig. 15A [37]. 

O Driscoll reports that several polymer-monomer combinations were used in the controlled preparation of homo- and block polymers by ultrasonic radiation(108). Similarly, Fujiwara reports the preparation of poly(styrene-b-methyl methacrylate) by ultrasonic degradation of polystyrene(109). The utility of ultrasonic irradiation is limited since yields are usually low, and the block copolymer is often contaminated with relatively large amounts of the homopolymers. 

Winnik et al. [53] used time-resolved fluorescence spectroscopy (direct non-radi-ative energy transfer experiments) to determine the interface thickness in films of symmetric poly(styrene-fc-methyl methacrylate) (PS-PMMA) block copolymers labeled at their junctions with either a 9-phenanthryl or a 2-anthryl group. The corrected donor fluorescence decay profiles were fitted to simulated fluorescence decay curves in which the interface thickness 8 was the only adjustable parameter. The optimum value of the interface thickness obtained was 6 = 4.8 run. In similar studies [54—57], the same authors determined the interface thickness value 6 = 1.6 nm in mixtures of two symmetrical poly(isoprene-b-methyl methacrylate) (PI-PMMA) block copolymers of similar molar mass and composition [54] the interface thickness value 8 = 1.1 nm for the lamellar structures formed in films of symmetric PI-PMMA diblock copolymers bearing dyes at the junctions [55] a cylindrical interface thickness value of d slightly smaller than 1.0 nm in films consisting of mixtures of donor- and acceptor-labeled PI-PMMA (29vol% PI) that form a hexagonal phase in the bulk state [56] and the interface thickness 8 = 5 run on the diblock copolymer poly(styrene-l>-butyl methacrylate)(PS-h-PBMA) [57]. 

C. Auschra, R. Stadler, and LG. Voigt-Martin, Poly (styrene-b-methyl methacrylate) block copolymers as compatibilizing agents in blends of poly (styrene-co-acrylonitrile) and poly (2, 9-dimethyl-l, 4-phen-ylene ether) 2. Influence of concentration and molecular weight of symmetric block copolymers. Polymer, 34 2094r-2110,1993. 

Block copolymers are also cast or spin coated for evaluation by a range of techniques, and these are discussed later in this chapter (see Section 5.3.4.6). Chen and Thomas [113] used force modulation microscopy (FMM), a SPM technique that measures relative elasticity across a surface, to study the block copolymer morphology of roll cast and spin coated films. Three model samples were investigated unannealed poly(styrene-butadiene-styrene) triblock copolymer, fabricated from solution using roll casting, cut perpendicular to the oriented cylinders with a razor blade annealed and unannealed poly(styrene-h-methyl methacrylate diblock copolymer spin coated from solution and an ultrathin film of a rod-coil diblock copolymer cast from a dilute solution onto a carbon coated mica sheet. Triblock copolymers were strained in tension using a copper grid as support and... 

Figure 9.17 Plot of log [i ]M versus retention volume for various polymers, showing how different systems are represented by a single calibration curve when data are represented in this manner. The polymers used include linear and branched polystyrene, poly(methyl methacrylate), poly(vinyl chloride), poly(phenyl siloxane), polybutadiene, and branched, block, and graft copolymers of styrene and methyl methacrylate. [From Z. Grubisec, P. Rempp, and H. Benoit, Polym. Lett. 5 753 (1967), used with permission of Wiley.]...

The reaction of ACPC with linear aliphatic amines has been investigated in a number of Ueda s papers [17,35,36]. Thus, ACPC was used for a interfacia] polycondensation with hexamethylene diamine at room temperature [17] yielding poly(amide)s. The polymeric material formed carried one azo group per repeating unit and exhibited a high thermal reactivity. By addition of styrene and methyl methacrylate to the MAI and heating, the respective block copolymers were formed. 

Yagci and Deniziigil [44] applied the method of partial decomposition of MAIs introducing styrene and methyl methacrylate blocks into poly(amide)s. The poly-(amide)-based MAI had been prepared by a reaction of AIBN with formaldehyde (see Scheme 10). Evidently, since each unit of the preformed MAI carries one azo group, there are enough azo sites in every MAI molecule for a controlled and adjustable partial decomposition. 

There are some indications that the situation described above has been realized, at least partially, in the system styrene-methyl methacrylate polymerized by metallic lithium.29 29b It is known51 that in a 50-50 mixture of styrene and methyl methacrylate radical polymerization yields a product of approximately the same composition as the feed. On the other hand, a product containing only a few per cent of styrene is formed in a polymerization proceeding by an anionic mechanism. Since the polymer obtained in the 50-50 mixture of styrene and methyl methacrylate polymerized with metallic lithium had apparently an intermediate composition, it has been suggested that this is a block polymer obtained in a reaction discussed above. Further evidence favoring this mechanism is provided by the fact that under identical conditions only pure poly-methyl methacrylate is formed if the polymerization is initiated by butyl lithium and not by lithium dispersion. This proves that incorporation of styrene is due to a different initiation and not propagation. 

In summary, we have examined several new methods for cleaving ester groups in poly(styrene-b-alkyl methacrylates). Short blocks of methyl methacrylate are very difficult to hydrolyze, but can be cleaved with reagents such as lithium iodide and potassium trimethylsilanolate. These latter reagents, however, result in side-reactions which appear to crosslink the polymer. 

The idea of the preparation of porous polymers from high internal phase emulsions had been reported prior to the publication of the PolyHIPE patent [128]. About twenty years previously, Bartl and von Bonin [148,149] described the polymerisation of water-insoluble vinyl monomers, such as styrene and methyl methacrylate, in w/o HIPEs, stabilised by styrene-ethyleneoxide graft copolymers. In this way, HIPEs of approximately 85% internal phase volume could be prepared. On polymerisation, solid, closed-cell monolithic polymers were obtained. Similarly, Riess and coworkers [150] had described the preparation of closed-cell porous polystyrene from HIPEs of water in styrene, stabilised by poly(styrene-ethyleneoxide) block copolymer surfactants, with internal phase volumes of up to 80%. 

In another recent example, dtrate-capped Au NPs are modified with 1-dodeca-nethiol in a first step. These premade nanoparticles were encapsulated with block copolymers such as poly(styrene-block-acrylic acid) (PS-b-PAA) and poly(methyl-methacrylate-block-acrylic acid) (PMMA-b-PAA) leading to core-shell hybrid materials. The Au NP diameters are 12 and 31 nm with average shell thickness of about 15 nm [121] (Scheme 3.18). 

Poly(isobutylene-Woc/c- -caprolactone) copolymer Poly(isobutylene-Woc/c-styrene) copolymer Poly(isobutylene-Woc/c-isobutyl vinyl ether) copolymer Poly(isobutylene-Woc/c-a-methylstyrene) copolymer Poly(isobutylene-block-methyl vinyl ether) copolymer Poly(isobutylene-b/oc/c-methyl methacrylate) copolymer... 

The order of monomer addition is important. For example, to prepare an AB type block copolymer of styrene and methyl methacrylate, st ene must be polymerized first using a monofunctional initiator and when styrene is completely reacted, the other monomer MMA must be added. The copolymer would not form if MMA were polymerized first, because living poly(methyl methacrylate) is not basic enough to add to styrene. The length of each block is determined by the amount of corresponding monomer which was provided. To produce ABA type copolymer by monofunctional initiation, B can be added when A is consumed, and A added again when B is consumed. This procedure is possible if the anion of each monomer sequence can initiate polymerization of the other monomer. Multiblock copolymers can also be made in this way. 

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