Syndiotactic Poly Methyl Methacrylate Research Articles

Preparation of polyhedral oligomeric silsesquioxane‐containing block copolymer with well‐controlled stereoregularity

ABSTRACTPreparation of functional domains with a spacing of 10 nm is a benchmark set to fabricate next‐generation electronic devices. Organic–inorganic block copolymers form well‐ordered microphase separations with very small domain sizes. The design and preparation of a novel block copolymer consisting of syndiotactic polymethyl methacrylate (st‐PMMA) and polyhedral oligomeric silsesquioxane (POSS)‐functionalized polymethacrylate, designated as st‐PMMA‐b‐PMAPOSS, which can recognize functional molecules, are reported. The st‐PMMA segments form a helical structure and encapsulate C60 in the helical nanocavity, leading to the formation of an inclusion complex. Although the ordering of the domains is not high, C60 domains that are in a quasi‐equilibrium state, with about 10‐nm domain spacings, are generated using st‐PMMA‐b‐PMAPOSS that can recognize functional molecules. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2181–2189

Preparation of High-Density Polymer Brushes with a Multihelical Structure.

It is well-known that a mixture of isotactic and syndiotactic polymethyl methacrylate (PMMA) forms a stereocomplex consisting of a multihelical structure in which an isotactic chain is surrounded by a syndiotactic chain. Here, we report the basic structure of the stereocomplex formed when the syndiotactic PMMA chains are tethered to a silicon substrate and form a high-density polymer brush. The influence of geometric confinement was investigated by preparing the high-density polymer brushes on a flat and spherical substrate. In both cases, mixing the untethered isotactic PMMA with the grafted syndiotactic PMMA led to the formation of a stereocomplex with a multihelical structure. Static contact angle measurements showed a hindered surface mobility at the outermost surface of the polymer brush, indicating that the stereocomplex forms a crystalline structure. A syndiotactic polymer brush with substituted fluoroalkyl groups was prepared to increase the contrast for grazing incidence wide-angle X-ray diffraction (GIWAXD) measurements. The GIWAXD results verified that the stereocomplex forms a crystalline structure oriented perpendicular to the substrate with a relatively low degree of orientation.

Polymerizations of methyl methacrylate and rac-lactide by zinc(II) precatalyst containing N-substituted 2-iminomethylpyridine and 2-iminomethylquinoline

The reaction of [ZnCl2] with N-cyclopentyl-1-(quinolin-2-yl)methanimine (LA), N-cyclohexyl-1-(quinolin-2-yl)methanimine (LB), N-cyclohexyl-1-(pyridin-2-yl)methanimine (LC), 2,6-diethyl-N-(pyridin-2-ylmethylene)aniline (LD), N-cyclopentyl-1-(pyridin-2-yl)methanimine (LE), and N-phenyl-(pyridin-2-yl)methanimine (LF) in ethanol produced the bidentate [(NN′)ZnCl2] complexes, [LAZnCl2], [LBZnCl2], [LCZnCl2], [LDZnCl2], [LEZnCl2] and [LFZnCl2], respectively. The molecular structures revealed that the zinc in [LnZnCl2] (Ln = LA − LD) showed a distorted tetrahedral geometry involving two nitrogens of N,N’-bidentate ligands and two chloride ligands. Most of these initiators were effective for polymerization of methyl methacrylate (MMA) and polymerization of rac-lactide (rac-LA). [LCZnCl2] (with N-cyclohexyl substituted at imine-pyridine moiety) exhibited the highest catalytic activity for MMA polymerization in the presence of modified methylaluminoxane (MMAO) with an activity of 3.33 × 104 g PMMA/mol·Zn·h at 60 °C, giving moderate syndiotactic poly methyl methacrylate (PMMA) with high molecular weight (9.62 × 105 g/mol). The dimethyl derivatives [LnZnMe2] (Ln = LA − LF), generated in situ, polymerized rac-LA with moderate activity and yielded a polylactide (PLA) with good number-average molecular weights and narrower polydispersity indices (PDIs). [LAZnMe2] effectively initiates the ring-opening polymerization (ROP) of rac-LA to attain heterotactic PLA (Pr = 0.91).

Synthesis of tellurium containing syndiotactic polymethyl methacrylate using diphenyl ditelluride as a novel initiator

The synthesis of syndiotactic polymethyl methacrylate containing tellurium by using diphenyl ditelluride in the dioxan at (60 ± 0.1)°C for 2 h has been carried out. The presence of tellurium in the polymer has been confirmed qualitatively as well as by induced coupled plasma mass spectroscopy (ICP-MS). The electron spin resonance spectrum shows the presence of TėPh, and value of gyromagnetic constant g has been calculated as 2.2203. The Tg of the polymer, measured by DSC, is 105°C. The syndiotactic nature has been confirmed by FTIR and NMR spectroscopy and DSC. The system follows ideal kinetics with activation energy 66 kJ mol−1. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1017–1022, 2006

Molecular dynamics simulation study of the effect of PMMA tacticity on free volume morphology in membranes

The effect of the tacticity of poly methyl methacrylate (PMMA) on the morphology of free volume in PMMA membranes was studied by using a molecular dynamics simulation technique. The chain flexibility, chain interaction, end-to-end distance of a chain and the time course of the free volume variation in the various stereo-regular PMMA, were obtained by an MD simulation technique. Simulation results depict that the construction of distinct tacticity has a significant influence on the flexibility of a molecular chain and the morphology of free volume in the syndiotactic (s-) and isotactic (i-) PMMA oligomers. MD calculation of the dynamic microstructure of a PMMA matrix shows that the s-PMMA membrane gives less flexibility in the backbone and a longer end-to-end distance than in the i-PMMA membrane. The less flexibility and longer end-to-end distance in the s-PMMA matrix causes the shapes and sizes of s-PMMA free volume to be longer and larger than those in an i-PMMA membrane. Furthermore, by adopting conformation energy minimization and molecular dynamics simulation techniques, various tacticity models of PMMA were constructed and their effect on the size of accessible free volume and free volume morphology was analyzed. Finally, the adsorbed gas on the surface free volume in s-PMMA was also compared with i-PMMA membrane.

Synthesis of arsenic containing polymethylmethacrylate using p-acetyl benzylidene triphenyl arsonium ylide as photoinitiator

Arsenic containing syndiotactic polymethylmethacrylate (PMMA) using p-ABTAY (p-acetyl benzylidene triphenyl arsonium ylide)in benzene as the photoinitiator at 30 ± 0.2°C has been synthesized. The system follows non-ideal kinetics ( R p ∝ [ I] 0.25 [M]) due to both primary radical termination and degradative chain transfer reaction. The glass transition temperature of PMMA is 145°C. Analysis of the polymer by SEM technique shows the presence of arsenic in it. The polymer has been characterized by Infra-red spectroscopy.

Synthesis and characterization of hydrogenated poly[alkylmethacrylate(-b-styrene)-b-butadiene-b-(styrene-b-) alkylmethacrylate] triblock and pentablock copolymers

Triblock and pentablock copolymers of the X(Y)B(Y)X type have been synthesized by the sequential living anionic polymerization of butadiene (B), styrene (Y) and alkylmethacrylate (X), respectively. The diadduct of t-BuLi onto m-diisopropenylbenzene ( m-DIB) has been used as a difunctional initiator. Methylmethacrylate (MMA), t-butylmethacrylate (tBMA) and isobornylmethacrylate (IBMA) have been used as precursors of the outerblocks X. The polybutadiene (PBD) midblock that contains ca 42–45% 1,2-units has been selectively hydrogenated into a saturated poly(ethylene-co-1-butene) (PEB) block. The homogeneous hydrogenation catalysis has no deleterious effect on the copolymer integrity. These completely soluble thermoplastic elastomers have been characterized by FTi.r., n.m.r., d.s.c. and d.m.a. The PEB midblock has a low T g (−50°C) and a small propensity to crystallize. The effect of hydrogenation on the morphology and mechanical properties depends on the outer block. Upon hydrogenation of the PBD midblock in polymethylmethacrylate (PMMA) and polyisobornylmethacrylate (PIBMA) containing triblock copolymers, the ultimate tensile strength is increased (except for a hard block content > 50%) due to a sharper phase separation, whereas the elongation at break is decreased. The extent of phase separation is reduced in polyt-butylmethacrylate(PtBMA) containing triblock copolymers upon hydrogenation and the ultimate tensile strength is slightly decreased. Stereocomplexation of the syndiotactic PMMA outerblocks is observed to occur upon blending with isotactic PMMA.

Analysis of band intensities in the IR spectra of macromolecular assemblies

Band intensities in the IR spectra of oscillator chain assemblies are calculated. It is shown that the dependences of the band intensity on temperature and on the concentration of the second conformation are nonlinear and are determined by the orientation of the vector of the oscillator dipole moment derivative with respect to the extension coordinate along the rotation axis. In the case of vibrations of the main chain, for bands with perpendicular dichroism, the contributions to the band intensity from the change in the orientation of the vector of the oscillator dipole moment derivative with respect to the extension coordinate and from the change in the vibration shape are compensated by each other. Bands with parallel dichroism, for which this compensation is absent, are more sensitive to changes in the chain conformation. This approach is illustrated by analysis of the vibrational spectra of isotactic and syndiotactic polymethyl methacrylate and polyethylene terephthalate.

Dynamic aspects of phase decomposition in reactive blends of polycarbonate and syndiotactic polymethyl methacrylate

AbstractDynamics of phase separation in bisphenol‐A polycarbonate (PC)/syndiotactic polymethyl methacrylate (sPMMA) blends has been investigated by means of time‐resolved light scattering. Solvent‐cast films of the PC/sPMMA blends were transparent, suggestive of miscible character. Several temperature jumps were carried out at a 50/50 PC/sPMMA composition from a homogeneous state (room temperature) into a two‐phase regime. The process of phase separation first occurred for some considerable period, then it was followed by phase dissolution driven by chemical reaction. The thermodegradative reaction of sPMMA triggered the dissolution process by probably forming PC/sPMMA graft or random copolymers at the interface, which eventually resulted in a single phase. However, annealing at elevated temperatures for an extended period could lead to cross‐linking, and thus a two‐phase structure could be fixed permanently. The early stage of spinodal decomposition was interpreted in terms of the linearized Cahn‐Hilliard theory. In the late stages of spinodal decomposition, the relationship between scattering peak wavenumber and time was found to obey a power law, but the exponents showed a strong dependence on temperature jumps. The temporal universal scaling failed due to the influence of the chemical reaction. © 1995 John Wiley & Sons, Inc.

Excited-state probing of associative and covalent macromolecules

Abstract

Miscibility studies on blends of polycarbonate with syndiotactic polymethyl methacrylate

AbstractMiscibility of bisphenol‐A polycarbonate (PC) and syndiotactic polymethyle methacrylate (sPMMA) blends was investigated by differential scanning calorimetry (DSC) and small‐angle light scattering. Cloud‐point measurements indicated the existence of both a lower critical solution temperature and an upper critical solution temperature, forming an immiscibility loop. This immiscibility gap was observed for PC blends with sPMMA of various molecular weights ranging from 8,300 to 55,000. The DSC study on solvent‐cast and coprecipitated PC/sPMMA blends from tetrahydrofuran solutions showed a single glass transition, shifting regularly with composition. The annealing of the 50/50 composition within the immiscibility loop exhibited dual glass transitions, but the system reverted to a single phase upon annealing above the loop. Phase dissolution took place during annealing above the loop, followed by thermoxidative branching (cross‐linking) reaction. Dry pellets of PC and sPMMA were melt mixed above the loop in a Mini‐Max mixer/molder; these molded blends exhibited a single phase. © 1993 John Wiley & Sons, Inc.

Association phenomena of PMMA in solutions and gels

AbstractStereocomplex formation of isotactic and syndiotactic polymethylmethacrylate (PMMA) could be demonstrated using X‐ray, NMR, and viscosity techniques. In this paper it is shown by measurements of viscosity and investigation of swelling properties that the association of isotactic and syndiotactic sequences of the polymer occurs as well in the solutions and gels of atactic PMMA. From the temperature dependence of the reduced specific viscosity and the swelling it can be deduced that association causes network formation due to microcrystalline regions which have a melting point range. In solutions of toluene with mixtures of isotactic and syndiotactic PMMA an intermolecular association, with atactic PMMA an intramolecular association is discussed. In chloroform no association could be observed.

Dipole moments of syndiotactic polymethylmethacrylate

Dipole moments of syndiotactic polymethylmethacrylate

Nuclear Relaxation in the Benzene–PMMA System

The nuclear relaxation of benzene protons in the benzene–polymethylmethacrylate (PMMA) system has been examined at concentrations up to 35 wt% PMMA. Systems prepared from isotactic and syndiotactic PMMA were studied. The polymer samples ranged in molecular weight between 4 × 104 and 2thinsp;× 106. The concentration dependence of the benzene spin–lattice relaxation time is independent of the mw and tacticity of PMMA and decreases with increasing polymer concentration. The benzene spin–lattice relaxation of samples containing 4 × 104 mw PMMA was resolved into dipolar contributions from: (1) intermolecular pairs of protons; (2) intermolecular pairs of benzene protons; (3) intermolecular benzene–polymer proton pairs. Selective deuterium substitution was used to separate these effects. T2, the benzene spin–spin relaxation time, showed sensitivity to the molecular weight and stereoregularity of the polymer. In contrast to the behavior found in nonpolymeric solutions, (T2 / T1) ratios much greater than unity were observed (greater than 40 in extreme cases). These results cannot be explained on the basis of solution viscosity. Rather, they reflect the microscopic inhomogeneity of concentrated polymer solutions, and the migration of solvent molecules between local environments of different polymer concentrations. A qualitative mathematical description of the migration process and its effects on T2 is presented.

Thermal degradation of polymethylmethacrylate. Energies of activation

AbstractRate constants of the thermal degradation of polymethylmethacrylate fractions have been measured over a range of temperatures, and the ARRHENIUS equations have been derived. There are two degradation reactions for this polymer; one “fast” reaction, which is chain‐end initiated, due to double‐bonded chain‐end polymer molecules and one “slow” reaction, which is initiated at random. The energy of activation for the fast reaction is much smaller than that of the slow reaction. Both show two levels of energies of activation proceeding from long to short chains. These energies of activation increase with decreasing chain length of the polymer as expected from theory. Whereas the differences in energies for the fast reaction are in agreement with a mechanism consisting of chain‐end initiation, depropagation, and second‐order termination, a reasonable value for the overall energy for the slow reaction is only obtained for a first‐order termination process. Such a reaction is not unlikely, as the polymer film contains appreciable amounts of monomer at this stage of degradation. The energies of activation for the slow reaction increase with percentage conversion as long as some double‐bonded chain ends are still in the system. It has to be concluded that the degradation of isotactic and syndiotactic polymethylmethacrylate, which degrade by random initiation, also have a first‐order termination reaction. On the basis of the results reported here, the confusion in the literature concerning energies of activation for the thermal degradation of polymethylmethacrylate can be understood. These energies do not only depend on chain length but also on the mechanism of the degradation process, range of conversion, and percentage of double‐bonded chain ends in the system.

Complex Formations between Iso and Syndiotactic Polymethylmethacrylate in Solutions

LIQUORI1,2 showed the occurrence of a possible “stereocomplex” in dissolved mixtures of iso and syndiotactic polymethylmethacrylate (PMMA) in a ratio of 1/2 i/s PMMA and, on the basis of X-ray diffraction on the solid mixtures, suggested its possible structure1. After Liquori's first publication in 1965, we supposed that such a stereocomplex could also be shown by viscosity, light-scattering and refractive index measurements of solutions of isomer mixtures and by infrared spectral analysis of solid mixtures. The syntheses of the iso and syndiotactic3,4 isomers (I and S) are described in ref. 5. The molecular weights and nuclear magnetic resonance tacticities are given in Table 1. The preparation of the solutions is described in ref. 5. Chloroform is used as solvent.

A Comparison between the far ultraviolet absorption spectra of isotactic and syndiotactic polymethyl methacrylate in solution

Journal of Polymer Science Part B: Polymer LettersVolume 2, Issue 10 p. 925-931 Article A Comparison between the far ultraviolet absorption spectra of isotactic and syndiotactic polymethyl methacrylate in solution M. D'Alagni, M. D'Alagni Istituto Chimico, Centro Nazionale di Chimica delle Macromolecole (CNR) Sez. III, Universita' di Napoli, Napoli, ItalySearch for more papers by this authorP. De Santis, P. De Santis Istituto Chimico, Centro Nazionale di Chimica delle Macromolecole (CNR) Sez. III, Universita' di Napoli, Napoli, ItalySearch for more papers by this authorA. M. Liquori, A. M. Liquori Istituto Chimico, Centro Nazionale di Chimica delle Macromolecole (CNR) Sez. III, Universita' di Napoli, Napoli, ItalySearch for more papers by this authorM. Savino, M. Savino Istituto Chimico, Centro Nazionale di Chimica delle Macromolecole (CNR) Sez. III, Universita' di Napoli, Napoli, ItalySearch for more papers by this author M. D'Alagni, M. D'Alagni Istituto Chimico, Centro Nazionale di Chimica delle Macromolecole (CNR) Sez. III, Universita' di Napoli, Napoli, ItalySearch for more papers by this authorP. De Santis, P. De Santis Istituto Chimico, Centro Nazionale di Chimica delle Macromolecole (CNR) Sez. III, Universita' di Napoli, Napoli, ItalySearch for more papers by this authorA. M. Liquori, A. M. Liquori Istituto Chimico, Centro Nazionale di Chimica delle Macromolecole (CNR) Sez. III, Universita' di Napoli, Napoli, ItalySearch for more papers by this authorM. Savino, M. Savino Istituto Chimico, Centro Nazionale di Chimica delle Macromolecole (CNR) Sez. III, Universita' di Napoli, Napoli, ItalySearch for more papers by this author First published: October 1964 https://doi.org/10.1002/pol.1964.110021002Citations: 32AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume2, Issue10October 1964Pages 925-931 RelatedInformation

Internal friction in stereoregular polymethyl methacrylate

AbstractNew stereospecific polymerization systems for methyl methacrylate are reported. The temperature dependence of the internal friction of the stereoregular forms of polymethyl methacrylate (PMMA) has been determined at frequencies of ca. 1 cycle/sec. Isotactic PMMA does not exhibit a side chain relaxation and its main chain relaxation is 66°C. lower than that of conventional PMMA. Syndiotactic PMMA exhibits exactly the same relaxations as conventional PMMA. Since the density and infrared absorption spectra of syndiotactic and conventional PMMA are also comparable and differ from the isotactic form, it is concluded that conventional radical‐initiated polymer is not truly atactic but has considerable syndiotactic character.

High resolution NMR spectra of isotactic and syndiotactic polymethyl methacrylate in chloroform solution

High resolution NMR spectra of isotactic and syndiotactic polymethyl methacrylate in chloroform solution