Star‐shaped POSS–methacrylate copolymers with phenyl–triazole as terminal groups,synthesis, and the pyrolysis analysis

Star‐shaped polyhedral oligomeric silsesquioxane (POSS)–methacrylate hybrid copolymers with phenyl–triazole as terminal groups had been designed and synthesized via sequential atom transfer radical polymerization (ATRP), azidation, and phenylacetylene‐terminated procedures, and the hybrid copolymers here could be denoted as POSS–(PXMA‐Pytl)₈, where X can be M, B, L, and S, represented four different methacrylate monomers, such as methacrylate (MMA), butyl methacrylate (BMA), lauryl methacrylate (LMA), and stearyl methacrylate (SMA), respectively. Thermal gravimetric analysis (TGA) and in situ Fourier transform infrared spectroscopy (FTIR) were applied for studying the thermal stability and degradation mechanism, and it was found that all of the POSS–(PXMA‐Cl)₈ and POSS–(PXMA‐Pytl)₈ copolymers exhibited excellent thermal stabilities, which had great potential in heat‐resistant material application. Different tendencies of decomposition temperatures at 5% and 10% weight loss (T₅ and T₁₀) dependent on the side‐chain length and terminal group species were investigated respectively. The longer alkyl side chains of the monomers, the lower thermal stabilities, and enhanced T₅ and T₁₀ were also shown with the introduction of phenyl–triazole groups instead of chlorine groups. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40652.     

Synthesis and characterization of PMMA‐b‐PBMA block copolymers by atom transfer radical polymerization

The synthesis of diblock copolymers using atom transfer radical polymerization, ATRP, of n‐butyl methacrylate, BMA, and methyl methacrylate, MMA, is reported. These copolymers were prepared from 2‐bromoisobutyryl‐terminated macroinitiators of poly(MMA) and poly(BMA), using copper chloride, CuCl,/N,N,N′,N″,N″‐pentamethyldiethylenetretramine, PMDETA, as the catalyst system, at 100°C in bulk and in benzonitrile solution. The block copolymers were characterized by means of size‐exclusion chromatography, SEC, and ¹H‐NMR spectroscopy. The SEC analysis of the synthesized diblock copolymers confirmed important differences in the molecular weight control depending on the reaction medium (solvent effect) and the chemical structure of the macroinitiator used. In addition, differential scanning calorimetry, (DSC) measurements were performed, showing for all the copolymers a phase separation. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2683–2691, 2002     

Morphology and rheological behaviors of poly(ethylene terephthalate) nanocomposites containing polyhedral oligomeric silsesquioxanes

Poly(ethylene terephthalate) (PET)/polyhedral oligomeric silsesquioxane (POSS) nanocomposites were prepared by in situ polymerization. Light scattering measurement suggested that there is significant change in molecular weight arising from gel formation by chemical crosslinking during polymerization. The thermal decomposition temperatures of the composites measured at 5 wt % weight loss were 5–10°C higher than that of PET. There is no significant change in other thermal properties. Scanning electron microscopy observations suggest that there is obvious phase separation in PET/POSS composites, composites containing 1 wt % of disilanolisobutyl and trisilanolisobytyl‐POSS show fine dispersions of POSS (30–40 nm in diameter), which arise from strong interfacial interactions between POSS and PET during polymerization. The viscosity of the composites increased with the addition of POSS. The observation of a plateau region of composites containing 1 wt % of POSS in the plot of log G′ vs. log G″ indicates strong interfacial interactions between POSS and PET. Sixty‐three percent and 41% increase in tensile strength and 300 and 380% increase in modulus were achieved in the composites containing 1 wt % of disilanol‐ and trisilanol‐POSS, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Incorporation of metallic POSS,POSS copolymers,and new functionalized POSS compounds into commercial dental resins

An array of polyhedral oligomeric silsesquioxane (POSS) compounds, including metal, methacrylate, and amine functional POSS, and POSS copolymers were incorporated into aromatic and aliphatic dental resins. Heptaphenyl‐propylamine POSS and methacrylate derivatives were synthesized by corner‐capping and Michael addition reactions, respectively. The POSS compounds were tested for solubility in commercial resins at concentrations of 1, 5, 10, and 15 wt %, followed by UV polymerization of all soluble combinations. The POSS compounds generally increased modulus and had an unpredictable effect on T_g. The modulus of the aliphatic resin increased 83% by incorporation of 15 wt % aluminum‐phenyl POSS, while aromatic resins saw a maximum modulus improvement of 18% at 30°C and 72% at 160°C by incorporating 1 wt % of heptaphenyl‐methacrylate POSS. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2856–2862, 2006     

Fabrication of composite films with poly(methyl methacrylate) and incompletely condensed cage‐silsesquioxane fillers

Polyhedral oligomeric silsesquioxane (POSS) is a promising nanofiller for tuning properties of optically transparent polymer materials. On the other hand, traditional completely condensed POSS (CC‐POSS) has a fundamental problem for fabricating optically transparent composite films; CC‐POSS has high crystallinity due to its symmetrical structure, resulting in aggregation in the polymer matrices. In this work, we have demonstrated that incompletely‐condensed POSS (IC‐POSS), which has an open‐cage structure, can be well dispersed in a poly(methyl methacrylate) (PMMA) matrix. IC‐POSS with various substituents were readily synthesized, and their composite films of PMMA were fabricated by solution‐casting method. High transparency was achieved with up to 30 wt % of the IC‐POSS fillers, while the CC‐POSS analogues caused phase separation with 10 wt % loading. Addition of the IC‐POSS fillers can improve thermal stability and control glass transition temperature by the substituent structure. Additionally, refractive index was tuned from 1.485 to 1.513. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46033.     

Rubber-modified epoxies. II. A reaction-induced phase separation observed in-situ and a posteriori with different methods

The reaction-induced phase separation in epoxy systems modified with rubber was firstly observed in situ with small angle X-ray scattering (SAXS), light transmission (LT), light scattering (LS), scanning electronic microscopy and transmission electronic microscopy techniques. The different observation windows of the SAXS, LT and LS methods allow us to follow the phase separation at two size levels. The selected system was bisphenol-A diglycidylether cured with 4,4′-diamino-3,3′-dimethyldicyciohexylmethane, in the presence of 15% wt of epoxy-terminated butadiene acrylonitrile random copolymers of different molecular weights. The phase separation inside the particles formed was followed first. Influences of precure temperature, rubber molecular weight, the postcure, vitrification and gelation on the evolution of the structure inside the particles are discussed. The real beginning of the phase separation is also discussed.     

Polyhedral oligomeric silsesquioxanes nanoreinforced methacrylate/epoxy hybrids

The aim of this study was to design novel binary and ternary copolymers based on methacrylate and/or epoxy monomers reinforced with 10 wt % mono‐/octafunctional polyhedral oligomeric silsesquioxanes (POSS) compounds bearing one or eight epoxy or methacrylate moieties. The experimental parameters such as temperature and time of reaction, comonomer ratio and the incorporation of various types of POSS that strongly influences the curing behavior, polymerization kinetics, glass transition temperature (T_g), thermostability and morphological structure of the obtained copolymers were investigated through DSC, FTIR, DMA, TGA, and SEM techniques. The obtained results evidenced that the complex kinetic mechanisms of curing reactions for the binary and ternary copolymers ± POSS influence the thermomechanical and morphological properties of the materials. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42912.     

Toughening effect of comonomer on acrylic denture base resin prepared via suspension copolymerization

In this article, three copolymers used as denture base resins were prepared via suspension copolymerization using butyl acrylate (BA), butyl methacrylate (BMA), or methyl acrylate (MA) with methyl methacrylate (MMA), respectively. The homopolymers and copolymers were characterized by ¹³C nuclear magnetic resonance (¹³C NMR). The influence of the three comonomers on the mechanical property was investigated in details and the fracture surfaces of copolymer specimens were examined using scanning electron microscopy (SEM). Meanwhile, the T_g values of three copolymers were examined by differential scanning calorimetry (DSC). The results indicate that, poly(methyl methacrylate) (PMMA) copolymers with BA, BMA, or MA have been successfully prepared via suspension copolymerization. The presence of BA, BMA, or MA could improve the mechanical property especially the impact strength, the toughness of the materials was remarkably improved. The toughening effect of BMA monomer is most significant. When the content of BA is 2 wt %, the flexural strength improves by 51% and the impact strength improves by 81.3%. The T_g values of three copolymers all decrease. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Preparation and characterization of copolymers containing (+)‐bornyl methacrylate and their racemate for positive‐tone photoresist

This study investigated the chemical behavior of polymers bearing cycloaliphatic bornyl units along with the steric difference of the chiral (+)‐bornyl methacrylate [(+)‐BMA] and racemic (±)‐BMA, expressed in the physical properties of the copolymers and the resist characteristics. To do this, a series of copolymers containing (+)‐bornyl methacrylate [(+)‐BMA] and (±)‐BMA] units was synthesized. Comonomers of tert‐butyl methacrylate (TBMA), methyl methacrylate (MMA), and maleic anhydride (MA) were used. The thermogravimetric curves, glass‐transition temperature (T_g), and molecular weight (MW) of the copolymers were evaluated. Exposure characteristics of chemical‐amplified positive photoresists comprising various copolymers were investigated. It was found that copolymers bearing (±)‐BMA have higher T_g and better thermostability than those of copolymers containing (+)‐BMA units. The copolymers with (±)‐BMA units, however, revealed an inert photochemical behavior on the positive‐tone photoresist. The patterning properties of the positive photoresist, composed of copolymers bearing (+)‐BMA and (±)‐BMA, and the photoacid generator (PAG) were also investigated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3538–3544, 2001     

Methacrylate-based block ionomers I: Synthesis of block ionomers derived from t-butyl methacrylate and alkyl methacrylates

Diblock and triblock copolymers of t-butyl methacrylate (tBMA) with 2-ethylhexyl methacrylate (EHMA) and n-hexyl methacrylate were prepared via alkyl lithium initiation and sequential addition techniques in THF at ?78°C. The tBMA blocks were quantiatively and selectively hydrolyzed to afford poly(methacrylic acid) (PMAA) blocks which were then neutralized with alkali metal bases to form block ionomers. The unhydrolyzed copolymers had a phase mixed morphology as evidenced by thermal analysis while the hydrolyzed and neutralized polymers were multiphase materials. The carboxylic acid and ioncontaning triblock copolymers formed gels in nonpolar solvents which could be disrupted by the addition of polar additives. Certain carboxylic acid and ioncontaining EHMA/tBMA diblock copolymers also showed this behavior. The triblock ionomers did not show thermoplastic flow prior to degradation, except at the lowest ionic content studied (2%).     

Light scattering of ideal random copolymers in bulk

Copolymerization is a useful way of modifying the physical properties of a material to meet specific needs, but it can result in a significant light scattering loss due to dielectric fluctuations in the material. Ideal random copolymers are known to be more transparent; however, the light-scattering properties of such copolymers in bulk have not been fully studied. In this paper, two representative ideal random copolymers were synthesized: methyl methacrylate (MMA)/benzyl methacrylate (BzMA) and MMA/2,2,2-trifluoroethyl methacrylate (TFEMA). The effects of copolymer composition and polymerization temperature on the light-scattering properties were investigated. Polarized light scattering (V_V) in copolymers was more sensitive to the polymerization temperature. Higher temperatures were necessary to homogenize the dielectric fluctuations and minimize excess light scattering. However, once the heterogeneous structures vanished, the copolymer bulk exhibited low scattering losses, which are comparable with homopolymers, over the entire range of copolymer compositions.     

Morphologies and structures in poly(<Emphasis Type="SmallCaps">l</Emphasis>-lactide-<Emphasis Type="Italic">b</Emphasis>-ethylene oxide) copolymers determined by crystallization,microphase separation,and vitrification

Morphologies and structures determined by crystallization of the blocks, microphase separation of the copolymers, and vitrification of PLLA block in poly(l-lactide-b-ethylene oxide) (PLLA-b-PEO) copolymers were investigated using microscopic techniques and synchrotron small angle X-ray scattering. The PLLA-b-PEO copolymer films were crystallized from two different annealing processes: melt crystallization (process A) or crystallized from glass state of PLLA block after quenching from melt state (process B). The relationship between the crystalline morphology and microstructure of the copolymers were explored using SAXS. The morphology and phase structure are predominated by crystallization of PLLA block, and greatly influenced by microphase separation of the copolymers. In process B, lozenge-shape and truncated lozenge-shaped PLLA crystals of nanometer scale can be observed. The crystalline morphology is markedly affected by the microstructure formed during the annealing process. Star-shaped morphologies stacked with PLLA single crystals were observed.     

Synthesis and characterization of ABA triblock copolymers of 2-hydroxyethyl methacrylate and n-butyl methacrylate by group transfer polymerization

Summary Difference ABA triblock copolymers (1) of 2-trimethylsilyloxyethyl methacrylate (TMS-HEMA) and n-butyl methacrylate (BMA) were prepared by group transfer polymerization (GTP) with a difunctional initiator. The polydispersities of the block copolymers were in 1.16 to 1.43 range. From selective and quantitative hydrolysis of poly (TMS-HEMA) segments of 1, block copolymers (2) of 2-hydroxyethyl methacrylate (HEMA) and BMA could be prepared. 2 showed different solubilities depanding on their compositions. From transmission electron micrographs of films casted from dilute solution of the polymers, it was found that microphase separation of the hydrophilic and hydrophobic domains occurs in different geometries.     

Gradient crystallinity and its influence on the poly(vinylidene fluoride)/poly(methyl methacrylate) membrane-derived by immersion precipitation method

Herein, phase inversion poly(vinylidene fluoride)/poly(methyl methacrylate) (PVDF/PMMA) microporous membranes were prepared at various PMMA concentration by immersion precipitation method. Increment in the PMMA concentration has a significant influence in the PVDF membrane crystallinity, which is studied by differential scanning calorimeter, X-ray diffractometer, and small-angle X-ray scattering analyses. Properties such as membrane bulk structure, porosity, hydrophilicity, mechanical stability, and water flux vary in terms of PMMA concentration. Porosity is increased, and tensile strength decreased when PMMA concentration is beyond 30 wt %. Thermodynamic instability during the liquid to solid phase separation and variation in the crystallinity has an intense effect on these membrane properties. Then, 70/30 blend membrane selected as optimum composition owing to the high porosity and pure water flux compared to other compositions. This membrane is modified with a composite filler derived from the graphene oxide and titanate crosslinked by chitosan. The antibacterial, antifouling, and bovine serum albumin separation studies reveal that the developed nanocomposite membrane is a potential candidate for the separation application. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48677.     

A comparative study on the thermally enhanced reorientation between random and diblock methacrylate copolymers with photo-cross-linkable mesogenic side groups by irradiating with linearly polarized ultraviolet light

The thermally enhanced photoinduced reorientation behavior of random and diblock copolymer films of methyl methacrylate and methacrylate with a photo-cross-linkable 4-(4-methoxycinnamoyloxy)biphenyl (MCB) side groups was investigated by irradiating with linearly polarized ultraviolet light and subsequently annealing. Random copolymers were synthesized by free radical copolymerization, while diblock ones were obtained by an atom transfer radical polymerization method with a PMMA macroinitiator. The photoinduced optical anisotropy was thermally amplified when the copolymer exhibited a liquid crystalline phase. The random copolymers with a high composition of MCB side groups reverted the orientation direction and inhibited molecular aggregation. For the diblock copolymers, the reorientation behavior was analogous to the methacrylate homopolymer with MCB side groups and transmission electron microscopy revealed a phase separation structure with molecular orientation of the MCB groups.     

Characterization and CO2 sorption properties of poly[methacryloxypropylheptacyclopentyl‐T8‐silsesquioxane‐ co‐3‐methacryloxypropyltris(trimethylsiloxy)silane]

Poly[methacryloxypropylheptacyclopentyl‐T8‐silsesquioxane (MAPOSS)‐co‐3‐methacryloxypropyltris(trimethylsiloxy)silane (SiMA)] was synthesized through free radical polymerization. The physical and carbon dioxide (CO₂) sorption properties of the copolymer membranes were investigated in terms of the MAPOSS content. As the MAPOSS content increases, the membrane density increased, suggesting a decrease in the fractional free volume. In addition, the thermal stability was improved with increasing the MAPOSS content. These are because of the polyhedraloligomericilsesquioxane (POSS) units that restrict the high mobility of poly(SiMA) segments. The glass transition temperature, T_g of the copolymers was single T_g based on the differential scanning calorimetry, suggesting that the copolymers were random and not phase separation. Based on the CO₂ sorption measurement, the POSS units play a role in reducing Henry's dissolution by suppressing the mobility of the poly(SiMA) component, while POSS units increase the nonequilibrium excess free volume, which contributes to the Langmuir dissolution. Based on these results, the introduction of MAPOSS unit is one of the effective ways to improved the thermal stability and CO₂ sorption property due to the enhancement of the polymer rigidity. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Preparation and properties of methyl methacrylate and fluoroacrylate copolymers for plastic optical fiber cladding

Copolymers of methyl methacrylate (MMA) and fluoroacrylate (FA), with different FA content (0–100 wt %), were prepared by bulk polymerization. The chemical structure was identified by ¹H‐NMR and other physical properties were measured by DSC, Abbé refractometer, X‐ray diffractometry, polarized optical microscopy, and DMA. The copolymers were confirmed as random copolymers by Fineman–Ross analysis and first‐order Markov statistics. Increasing the FA content from 0 to 100 wt % decreased the refractive index from 1.492 to 1.368. Copolymers with FA content higher than 70 wt % crystallized and led to low transparency and poor thermal properties. On the other hand, copolymers with FA content lower than 70 wt % was thermally stable (T_g was as high as 60°C) and transparent. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2082–2089, 2004     

Poly(methyl methacrylate) hybrid syntactic foams with hollow glass microspheres and polyhedral oligomeric silsesquioxanes

The study aims to produce poly(methyl methacrylate) (PMMA)-based lower density syntactic foams with hollow glass microspheres (HGMs) and to improve their mechanical properties by the addition of polyhedral oligomeric silsesquioxanes (POSSs) while maintaining the thermal properties of the neat polymer. First to understand the effect of POSS addition, PMMA–POSS composites with octaisobutyl and octaphenyl POSS were produced through extrusion. Higher relative flexural and impact strengths were obtained with POSS addition to PMMA. Obtaining more enhanced properties with octaphenyl POSS, PMMA-HGM-POSS hybrid syntactic foams were prepared with this additive. In general, the specific flexural strength and modulus of the PMMA syntactic foams were improved with the POSS loading, while the lower density and thermal properties of the PMMA syntactic foams were maintained. PMMA hybrid syntactic foams with 15 wt % HGMs and 0.25 wt % POSS exhibited 37.6% improvement in the specific flexural modulus with respect to the neat PMMA. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48368.     

ABA triblock copolymers containing polyhedral oligomeric silsesquioxane pendant groups: synthesis and unique properties

The synthesis and characterization of POSS containing ABA triblock copolymers is reported. The use of atom transfer radical polymerization (ATRP) enabled the preparation of well-defined model copolymers possessing a rubbery poly(n-butyl acrylate)(pBA) middle segment and glassy poly(3-(3,5,7,9,11,13,15-heptaisobutyl-pentacyclo[9.5.1.1^3,9.1^5,15.1^7,13]-octasiloxane-1-yl)propyl methacrylate(p(MA-POSS)) outer segments. By tuning the relative composition and degree of polymerization (DP) of the two segments, phase separated microstructures were formed in thin films of the copolymer. Specifically, dynamic mechanical analysis and transmission electron microscopy (TEM) observations reveal that for a small molar ratio of p(MA-POSS)/pBA (DP=6/481/6) no evidence of microphase separation is evident while a large ratio (10/201/10) reveals strong microphase separation. Surprisingly, the microphase-separated material exhibits a tensile modulus larger than expected (ca. 2×10⁸ Pa) for a continuous rubber phase for temperatures between a pBA-related T_g and a softening point for the p(MA-POSS)-rich phase. Transmission electron microscopy (TEM) images with selective staining for POSS revealed the formation of a morphology consisting of pBA cylinders in a continuous p(MA-POSS) phase. Thermal studies have revealed the existence of two clear glass transitions in the microphase-separated system with strong physical aging evident for annealing temperatures near the T_g of the higher T_g phase (p(MA-POSS). The observed aging is reflected in wide-angle X-ray scattering as the strengthening of a low-angle POSS-dominated scattering peak, suggesting some level of ordering during physical aging. The T_g of the POSS-rich phase observed in the microphase separated triblock copolymer was nearly 25 °C higher than that of a POSS-homopolymer of the same molecular weight, suggesting a strong confinement-based enhancement of T_g in this system.     

Thermal decomposition of copolymers of methyl methacrylate and alkyl methacrylates obtained from a CSTR

Thermal decomposition of the copolymers of methyl methacrylate (MMA) with ethyl methacrylate (EMA) or n-butyl methacrylate (BMA) were investigated. The copolymers were obtained in a continuous stirred tank reactor (CSTR) using toluene and benzoyl peroxide, as solvent and initiator, respectively, at 80C. The volume was 1.2 litters and residence time was 3 hours. The thermal decomposition followed the second order kinetics for both MMA/EMA and MMA/BMA copolymers, which were almost in accordance with the order of copolymerization in a CSTR. The activation energies of thermal decomposition were in the ranges of 32-37 kcal/mol and 27-37 kcal/mole for MMA/EMA and MMA/BMA copolymers, respectively and a good additivity rule was observed against each composition for both copolymers. The thermogravimetric trace curve agreed well with the theoretical calculation.