Post-polymerization Modification Research Articles

Kinetics of TiCl4 Vapor Phase Infiltration (VPI) into PMMA and the Resulting Thermophysical and Optical Properties of the TiOx -PMMA Hybrids

Vapor phase infiltration (VPI) is a post-polymerization modification technique that imbues inorganic materials into polymers to create organic-inorganic hybrid materials with new properties distinct from the parent polymer. While several VPI precursor-polymer chemistries have been explored, a lack of chemical intuition remains for fully understanding the thermodynamics and kinetics that govern the VPI process. This study seeks to continue to build this knowledge by examining the VPI process kinetics for TiO2 infiltration into PMMA via the use of TiCl4 and H2O precursors. In this research, polymethylmethacrylate / TiO2 hybrid materials are prepared using VPI. The depth of infiltration of the TiO2species into ~200 nm PMMA thin films is studied using x-ray photoelectron spectroscopy (XPS), Fourier-transform infrared (FTIR) spectroscopy and spectroscopic ellipsometry. The kinetics for TiCl4 infiltration increases with both VPI process temperature and TiCl4 exposure time. However, the rates of infiltration are considerably slower than those observed in the more commonly studied trimethylaluminum (TMA) / PMMA system. Even at 150 °C, process times of at least 12 hours are required to fully infiltrate a 200 nm PMMA film whereas using TMA similar films are fully infiltrated within 1 hour at the same process temperature. Films that we believe to be fully infiltrated at 150 °C and 24 hours of TiCl4 exposure have a 6 at% Ti in the innermost bulk, as determined by XPS. Interestingly, unlike AlOx-PMMA hybrids, these TiOx – PMMA hybrids exhibit significant changes in their optical properties. Increased titanium loading leads to a 4% increase in refractive index and increased UV absorbance in the UV range of 270-350nm. Furthermore, films infiltrated at 150 °C and 24 hours of TiCl4 exposure had a 50 % and 70 % reduction in coefficients of thermal expansion (CTE) below and above Tg respectively. Reduced CTE trends with increased titanium loading. We will discuss possible opportunities to use these new properties for various applications.This project is supported by the Laboratory Directed Research and Development program at Sandia National Laboratories, a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International Inc. for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.

Poly(2-oxazoline)s as Stimuli-Responsive Materials for Biomedical Applications: Recent Developments of Polish Scientists.

Poly(2-oxazoline)s are the synthetic polymers that are the products of the cationic ring-opening polymerization (CROP) of 2-oxazoline monomers. Due to their beneficial properties, from which biocompatibility, stealth behavior, high functionalization possibilities, low dispersity, stability, nonionic character, and solubility in water and organic solvents should be noted, they have found many applications and gained enormous interest from scientists. Additionally, with high versatility attainable through copolymerization or through post-polymerization modifications, this class of polymeric systems has been widely used as a polymeric platform for novel biomedical applications. The chemistry of polymers significant expanded into biomedical applications, in which polymeric networks can be successfully used in pharmaceutical development for tissue engineering, gene therapies, and also drug delivery systems. On the other hand, there is also a need to create ‘smart’ polymer biomaterials, responsive to the specified factor, that will be sensitive to various environmental stimuli. The commonly used stimuli-responsive biomedical materials are based mostly on temperature-, light-, magnetic-, electric-, and pH-responsive systems. Thus, creating selective and responsive materials that allow personalized treatment is in the interest of the scientific world. This review article focuses on recent discoveries by Polish scientists working in the field of stimuli-responsive poly(2-oxazoline)s, and their work is compared and contrasted with results reported by other world-renowned specialists.

Alternating Methyl Methacrylate/n-Butyl Acrylate Copolymer Prepared by Atom Transfer Radical Polymerization.

Poly(methyl methacrylate/n-butyl acrylate) [P(MMA/BA)] copolymer with an alternating structure was synthesized via an activator regenerated by electron transfer (ARGET) atom transfer radical (co)polymerization (ATRP) of 2-ethylfenchyl methacrylate (EFMA) and n-butyl acrylate (BA) with subsequent postpolymerization modifications (PPM). Due to the steric hindrance of the bulky pendant group of EFMA, as well as the low reactivity ratio of BA in copolymerization with methacrylates, copolymerization of EFMA and BA generated a copolymer with a high content of alternating dyads. A subsequent PPM procedure of the alternating EFMA/BA copolymer was comprised of the hydrolysis of a tertiary ester by trifluoroacetic acid and methylation by (trimethylsilyl)diazomethane. After the modifications, the architecture of the obtained alternating MMA/BA copolymers was compared with gradient and statistical copolymers with overall similar compositions, molecular weights, and dispersities. 13C NMR indicated the absence of either MMA/MMA/MMA or BA/BA/BA sequences, in contrast to an abundance of homotriads in either the statistical or especially in the gradient copolymer. All three copolymers had similar glass transition temperatures, as measured by differential scanning calorimetry (DSC), but the alternating copolymer had the narrowest range of glass transition.

Chemically Recyclable CO2‐Based Solid Polyesters with Facile Property Tunability

Back Cover: In article 2200341, Bo-Lin Lin and co-workers discover a completely chemically recyclable polyester with high molecular weight, which originates from inexpensive CO2 and 1,3-butadiene. Furthermore, the material properties can be tailored via photo-initiated post-polymerization modification, which causes light blue fluorescence.

Activated polyallene as versatile substrate for efficient preparation of fluorinated composite

Introduction of fluorine into composites has been a subject of intense research because it brings about significant improvements in the performance of the composites. In particular, fluorine-containing composites exhibit excellent thermal stability, good chemical stability and low surface energy. However, the design of fluorine-containing composites is limited by the current polymerization and modification techniques. Herein, a series of double-bond-containing poly(phenoxyallene) (PPOA) polymers with tunable structure were facilely prepared through reversible addition-fragmentation chain transfer (RAFT) polymerization. To identify the RAFT polymerization conditions, RAFT homopolymerization of phenoxyallene (POA) was firstly conducted as a typical reaction. The effects of chain transfer agent (CTA), substituent of POA, temperature, and solvent were systematically investigated. Notably, highly efficient thiol-ene click reaction can be used for the direct modification of PPOA without further polymeric functionality transformation. When fluorinated thiol was used as reactant, a functional fluorine-containing polymer could be simply achieved, demonstrating the highly efficient efficiency of the postpolymerization modification. Considering the simple RAFT polymerization condition and excellent reactivity of double bonds in polymer structure, this thiol-ene postpolymerization modification might be a versatile platform for the precise fabrication of a broad variety of functional composites, especially for fluorine-containing composites.

Diazoacetates as Terminating Agents in Living Ring-Opening Metathesis Polymerization: Synthesis of Chain-End-Functionalized Polymers

We report herein a simple, efficient strategy to access diverse end-functionalized polymers from a living ring-opening metathesis polymerization process using diazoacetates as a new terminating agent. Such a terminating process occurs via a C═C bond-forming reaction between the chain-end ruthenium carbenes and the diazoacetates, resulting in the rapid construction of a unique, α,β-unsaturated carbonyl motif at more than 95% of the chain end within 5 min. A variety of easily accessible and diversely substituted diazoacetates could be used, allowing for the facile introduction of an additional panel of useful functionalities at the polymer chain end. Diverse postpolymerization modifications, including Michael addition, “click” reaction, and chain extension, have been further demonstrated.

A Bifunctional Polymeric Coating for the Co-Immobilization of Proteins and Peptides on Microarray Substrates.

The analytical performance of the microarray technique in screening the affinity and reactivity of molecules toward a specific target is highly affected by the coupling chemistry adopted to bind probes to the surface. However, the surface functionality limits the biomolecules that can be attached to the surface to a single type of molecule, thus forcing the execution of separate analyses to compare the performance of different species in recognizing their targets. Here, we introduce a new N,N-dimethylacrylamide-based polymeric coating, bearing simultaneously different functionalities (N-acryloyloxysuccinimide and azide groups) to allow an easy and straightforward method to co-immobilize proteins and oriented peptides on the same substrate. The bifunctional copolymer has been obtained by partial post-polymerization modification of the functional groups of a common precursor. This strategy represents a convenient method to reduce the number of analyses,therefore possible systematic or random errors, besides offering a drastic shortage in time, reagents, and costs.

Postpolymerization modification of a sulfonyl fluoride‐decorated polynorbornene using the sulfur‐fluoride exchange click reaction

AbstractThis contribution describes the ring opening metathesis polymerization of a sulfonyl fluoride decorated polynorbornene and its postsynthetic modification using the sulfur‐fluoride exchange “click” reaction.

Metal-free and ecofriendly photoluminescent nanoparticles for visualization of latent fingerprints, anticounterfeiting, and information encryption

Visualization of latent fingerprints (LFPs) on different substrates is a significant challenge for security forces in crime scene, which the highly fluorescent materials with maximum brightness and contrast for rapid detection by simple instruments are essential for this propose. In this study, the multi-color photoluminescent functional polymer nanoparticles based on oxazolidine (as fluorescent dye with concentration of 1 wt%) and a copolymer of methyl methacrylate (MMA)/2-(dimethylamino)ethyl methacrylate (DMAEMA) as matrix were synthesized by emulsion copolymerization and physical post-polymerization modification methods. After investigation of physicochemical and optical properties, the multi-color photoluminescent polymer powders were used for printing of security tags and visualization of LFPs by means of powder dusting strategy. The printed encoded security tags as quick responsive (QR) codes are highly fluorescent with maximum brightness and resolution in different colors. The photoluminescent polymer powders were used for fast and facile visualization of LFPs by powder dusting and fluorescence imaging using of smart phone camera under UV irradiation (365 nm). Results of fluorescence imaging indicated that the unique and personal details of fingerprints patterns are detectable by naked eye. Therefore, developed highly photoluminescent polymer powders for powder dusting and fluorescence imaging can provide reliable evidence to recognition of individual identity in a short time and by the least facilities.

Zwitterionic nano-objects having functionalizable hydrophobic core: Formation via polymerization-induced self-assembly and their morphology

Functionalizable poly(pentafluorophenyl methacrylate) (PPFPMA) and zwitterionic poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) are two polymers with an extremely different solubility. It is, therefore, almost impossible to synthesize their block copolymers in a controlled manner using a conventional approach. Herein, it is demonstrated, for the first time, that the synthesis and in situ formation of nanoassemblies of their diblock copolymers (PMPC-b-PPFPMA) can be achieved via polymerization-induced self-assembly using reversible addition-fragmentation chain-transfer dispersion polymerization in ethanol as a selective solvent. The PMPC was synthesized as the first block and further employed as a macro chain transfer agent (PMPC Macro-CTA) for the synthesis of the PPFPMA second block. In situ self-assembled nanostructures of the diblock copolymers were found to be mostly spherical with a varied degree of inter-micellar aggregation depending on the solid concentration and the relative length of the two blocks. Apparently, the limited chain mobility of the core-forming PPFPMA block, due to π-π stacking and hydrophobic interactions, hampered the formation of nanostructures of high-order morphologies. It is possible to perform core functionalization via post-polymerization modification with 1-pyrenemethylamine to yield fluorescently labeled nanostructures that may be applicable as biocompatible and non-fouling nanocarriers and nanosensors in the future.

Photochemistry of Azide‐Functional Polymers: Soluble Sulfoximine Polymers through Selective Nitrene–Sulfoxide Addition

AbstractOrganic azides are a common functional group in polymer chemistry. Upon irradiation, they form nitrenes which are usually exploited for crosslinking based on their “universal” reactivity allowing insertion into nearby C–H bonds. Herein, it is demonstrated that polymer‐bound perfluorophenyl azide groups selectively form sulfoximines when irradiated in the presence of an excess of sulfoxide, without observable crosslinking. Poly(4‐azido‐2,3,5,6‐tetrafluorobenzyl methacrylate) (carrying an azide group in every repeat unit) is prepared through azide–para‐fluoro postpolymerization modification of a 2,3,4,5,6‐pentafluorobenzyl‐functional precursor. Samples of the azide‐functional polymer are irradiated (λmax = 254 nm) in dichloromethane in the presence of varying amounts of five different sulfoxides. Products are characterized by 1H and 19F NMR spectroscopy, Fourier transform infrared spectroscopy, size exclusion chromatography, and differential scanning calorimetry. Irradiations for 7 h with a 40–70‐fold molar excess of sulfoxides gave soluble products with azide‐to‐sulfoximine conversions of 89–96%. This first example of a selective nitrene‐based reaction in the polymer arena shows that sulfoxide solvents must be avoided if crosslinking is desired and provides access to novel sulfoximine‐functional materials.

Polymer segmental dynamics near the interface of silica particles in the particle/polymer composites

We demonstrate an approach to examine the local segmental dynamics of a polymer near the interface of an inorganic filler by observing the rotational dynamics of the fluorescent probe at the chain ends of polymer brushes grafted onto the surface of the filler particles. Localization of the fluorescent probe was realized by designing and synthesizing fluorophore-tethered polystyrene (PS) brushes anchored on the surface of silica particles of controlled sizes. Fluorophore-functionalized telechelic PS with an azide functionality at the other chain end was achieved via a combination of atom transfer radical polymerization and post-polymerization modification. The azide-bearing PS chains were tethered to alkyne-functionalized particles via copper-catalyzed cycloaddition reaction. The molecular weight of the grafted polymer chains was controlled to be less than the critical entanglement molecular weight, and the chain density was controlled to be low enough so that the observed dynamics was not perturbed by the polymer brush conformation and brush-matrix polymer entanglement. The polymer dynamics near the surface of the particles at low concentrations was closely examined in the bulk film geometry by employing imaging rotational fluorescence correlation microscopy (irFCM). The observed polymer dynamics near the interface were not altered in the inorganic/polymer composite geometry when the surface did not have favorable interaction with the matrix polymer. The presented rational design of the chemical route and examination of local dynamics highlight a feasible approach to construct material systems with high complexities towards a deeper understanding of composite materials.

Pineapple Fiber Hybrids Prepared by the Fusion of radiation-induced Graft Polymerization and Kabachnik-Fields three-component Reaction (RIGP-KF3CR)

ABSTRACT The fusion of multicomponent reactions and polymer chemistry allows the synthesis of polymeric materials that contain special classes of molecules that are otherwise difficult to produce. In this study, a locally available nonwoven fabric composed of pineapple fibers and polylactic acid (piñatex) was modified by radiation-induced graft polymerization (RIGP) of vanillin methacrylate, a lignin-derived monomer. RIGP yielded organic hybrids made from a natural, renewable, and biodegradable substrate, and surface aldehyde groups from vanillin. The grafted fabric was prepared by gamma pre-irradiation at 50 kGy, exhibiting an increasing degree of grafting with increasing reaction time and monomer concentration. Post-polymerization modification carried out using Kabachnik-Fields three-component reaction (KF3CR) enabled the immobilization of amine and phosphite moieties on the fabric. FTIR, SEM-EDS and XPS analysis of 8 amine and phosphite combinations showed the presence of the corresponding elements and functional groups, indicating successful surface functionalization through RIGP-KF3CR. All modified natural fibers-based fabrics displayed enhanced thermal stability without obvious radiation degradation effects. Synthesized natural fibers contain α-aminophosphonate pendants which may be useful in the selective adsorption and recovery of industry valuable metals.

Vapor-Phase Infiltration of Polymer of Intrinsic Microporosity 1 (PIM-1) with Trimethylaluminum (TMA) and Water: A Combined Computational and Experimental Study.

Vapor-phase infiltration, a postpolymerization modification process, has demonstrated the ability to create organic-inorganic hybrid membranes with excellent stability in organic solvents while maintaining critical membrane properties of high permeability and selectivity. However, the chemical reaction pathways that occur during VPI and their implications on the hybrid membrane stability are poorly understood. This paper combines in situ quartz crystal microbalance gravimetry (QCM) and ex situ chemical characterization with first-principles simulations at the atomic scale to study each processing step in the infiltration of polymer of intrinsic microporosity 1 (PIM-1) with trimethylaluminum (TMA) and its co-reaction with water vapor. Building upon results from in situ QCM experiments and SEM/EDX, which find TMA remains within PIM-1 even under long desorption times, density functional theory (DFT) simulations identify that an energetically stable coordination forms between the metal-organic precursor and PIM-1's nitrile functional group during the precursor exposure step of VPI. In the subsequent water vapor exposure step, the system undergoes a series of exothermic reactions to form the final hybrid membrane. DFT simulations indicate that these reaction pathways result in aluminum oxyhydroxide species consistent with ex situ XPS and FTIR characterization. Both NMR and DFT simulations suggest that the final aluminum structure is primarily 6-fold coordinated and that the aluminum is at least dimerized, if not further "polymerized". According to the simulations, coordination of the aluminum with at least one nitrile group from the PIM-1 appears to weaken significantly as the final inorganic structure emerges but remains present to enable the formation of the 6-fold coordination species. Water molecules are proposed to complete the coordination complex without further increasing the aluminum's oxidation state. This study provides new insights into the infiltration process and the chemical structure of the final hybrid membrane including support for the possible mechanism of solvent stability.

Enzymatic synthesis, post-polymerization modification and cross-linking of functionalized poly(β-thioether ester) with pendant vinyl group

Vinyl-functionalized poly(β-thioether ester) (PVTE) was synthesized by enzyme-catalyzed polymerization using immobilized lipase B from Candida antarctica (CALB) for the first time. Four different functionalized monomers were prepared and three polymerization strategies including polycondensation (PC), ring-opening polymerization (ROP), and ring-opening and condensation copolymerization (ROCCP) were investigated. The influences of reaction conditions such as polymerization temperature, time, and monomer ratio on the molecular weight of functionalized poly(β-thioether ester)s were also studied. Both the homopolymer and copolymers were characterized by NMR, SEC, TGA and DSC. Moreover, these poly(β-thioether ester)s containing pendant double bonds toward postfunctionalization were demonstrated by photoinitiated thiol-ene click chemistry and Michael addition reaction, providing a way to cross-linked polyester gels.

Effects of trimethylaluminum vapor pressure and exposure time on inorganic loading in vapor phase infiltrated PIM-1 polymer membranes

Vapor phase infiltration (VPI) is a post-polymerization modification method for infusing inorganic clusters into a polymer to create organic-inorganic hybrid materials with properties that are unique from the parent polymer. The properties of these hybrid materials can vary with the amount of VPI generated inorganic loading. However, the relationship between VPI processing conditions and inorganic loading is still not fully understood. In this paper, the effects of VPI dose pressure and exposure time on inorganic loading are explored using the technologically relevant membrane material known as “polymer of intrinsic microporosity 1” (PIM-1). At sufficiently low dose pressures and infiltration times (i.e., before saturation), inorganic loading can be controlled with both vapor pressure and exposure time. However, inorganic loading appears to saturate for this system when the polymer's functional groups become fully populated with bound VPI precursors. These experimental results can be understood with the use of a recently developed reaction-diffusion model for VPI. Critical to applying this model to these post-deposition measurements is re-normalizing the mass loading to the total number of functional groups in the polymer.

The Divergent Reactivity of Lactones Derived from Butadiene and Carbon Dioxide in Macromolecular Synthesis.

The catalytic conversion of carbon dioxide and 1,3-butadiene into unsaturated lactone monomers provides an efficient route for converting sustainable carbon feedstocks into novel macromolecules. The chemical reactivity of this monomer is reviewed in order to highlight the many viable mechanistic pathways. Polymerization strategies, monomer alterations, and post-polymerization modifications are covered. The polymerization methods include radical, coordination, conjugate addition, ring-opening, olefin metathesis, and thiol-ene chemistries. Materials derived from these processes possess a wide range of function including responsiveness, degradability, adhesion, recyclability, and self-assembly. These aspects along with the advances in polymer chemistry that make them possible are discussed, along with a perspective on the future directions of the field.

Synthesis of PPC-graft-poly(PEOMA) Brush and PPC Gels via Post-polymerization Modification of Hydroxyl-Functionalized Poly(propylene carbonate)

Post-polymerization modification offers a facile and effective tool for adapting polymer properties. However, it has not been applied to poly(propylene carbonate) (PPC) as traditional PPC lacks sufficient functional groups along the polymer chain. In the present work, for the first time, hydroxyl-functionalized PPC has been prepared and used to construct PPC-brush and cross-linked polymer gels through post-polymerization modification approach. PPC-brushes in the form of PPC-graft-poly(PEOMA) were obtained with controllable brush length and brush density via “grafting from” a PPC-macroinitiator which was synthesized from esterification reaction of PPC-OH with 2-bromoisobutyryl bromide. PPC permanent networks in the form of dioxane gels were prepared by cross-linking PPC-OH with 4,4′-diphenylmethane diisocyanate (MDI). Rheological measurement of the gels showed that the cross-linking density scales linearly with the hydroxyl group density in PPC-OH. This work not only offers a facile strategy to realize the post-modification of PPC but also spurs the devising of innovative biodegradable materials with tailored molecular architectures.

Postpolymerization Modification and Topological Structure Design of Poly(vinyl ether)s Based on the Selective Addition Reaction of Electrophilic Selenium Reagent and Divinyl Monomers

Postpolymerization Modification and Topological Structure Design of Poly(vinyl ether)s Based on the Selective Addition Reaction of Electrophilic Selenium Reagent and Divinyl Monomers

Efficient Post-Polymerization modification of pendant aldehyde functional polymer via reductive etherification reaction

The aldehydes have always been a privilege in polymer science since the aldehyde carbonyl readily undergoes several reactions efficiently under mild conditions, ranging from non-aldol reactions to multicomponent reactions, mostly without any additive. In the current study, the versatility of the aldehyde group has been further exploited using the reductive etherification reaction (RER), which has proven to be a useful synthetic strategy to convert aldehyde or ketone carbonyls to ethers in the presence of organosilane compounds. For this purpose, a polymer platform containing pendant aldehyde units was synthesized via free radical polymerization (FRP) and modified with a variety of alcohols using chlorodimethylsilane (CDMS) as the reducing agent. The spectroscopic analyses indicated that pendant aldehydes successfully turned to corresponding ethers with quantitative or near quantitative RER efficiencies. The proposed strategy was also extended to thiols and the resultant polymers were found to be in thioacetal and/or thioether pendant forms. Given the growing demand for the development of new synthetic methodologies that can be adapted to the macromolecular level, a new insight into the modification of aldehyde-functionalized polymers has been introduced in this study.