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To prepare mono-dispersed transition metal nanoparticles on activated C supports is a long scientific challenge, due to low graphene surface energy. Few polar functional groups in activated C are only located on the plane edges, which are intrinsically difficult to prevent metal clustering, especially at elevated temperatures. This paper discusses a versatile method in preparing stable and uniform transition metal (Pt, Pd, Ti, etc.) nanoparticles (diameter ∼2 nm), using a newly-developed boron-substituted carbon (BCx) support, containing uniform B atoms distributed in the graphene layer structure, which provides a strong specific interaction; this interaction is formed by d-electrons back-donation from transition metals to the empty p-orbital in substituted B atoms. The BCx support shows good adsorption capacity of metal precursors in solutions, and securing the forming metal nanoparticles during thermal reduction at a high temperature (>500 °C). The resulting Pt/BC12 – with only 0.7 wt.% Pt content – exhibits very high surface activities. At ambient temperature, it offers an impressive hydrogen adsorption capacity at ∼0.5 wt.% per 500 m2/g surface area, which is more than 5 times higher than the corresponding activated C material with the same surface area.

A new family of porous boron-substituted carbon (BC x ) materials with controlled structure is investigated. The chemistry involves a B-precursor polymer, i.e., poly(borachlorophenyldiacetylene), containing inorganic additives (templates). At pyrolysis 85%). Above 600 °C, the amorphous carbon-like BC x materials containing up to 12% B have been prepared, which show an extended fused hexagonal ring structure with B-puckered curvature. This out of planar B moiety maintains its electron deficiency, due to limited π-electron delocalization, and exhibits super-activated properties to enhance H 2 binding energy (20–10 kJ/mol) and adsorption capacity. After removing the inorganic additives by water-washing, the resulting porous BC x shows a surface area 500–800 m 2 /g. Evidently, the pore size distribution is directly related to melting temperature and distribution of the inorganic salts. As the temperature increases to >1400 °C, the distorted ring structure gradually flatten out to form a multi-layer (crystalline) BC x structure. The resulting planar graphitic layer only can accommodate a reduced B content (

This paper discusses a facile route to prepare chain-end functionalized polyolefins containing a terminal functional group (OH, COOH, NH2, etc.), and polyolefin diblock copolymers containing a polyolefin block and a functional polymer block. The chemistry is centered at an in situ chain transfer reaction during metallocene-mediated α-olefin polymerization using two reactive chain transfer (CT) agents, including dialkylborane (R2B-H) and styrenic molecule/H2, to form polyolefin containing a reactive alkylborane and styrenic terminal group, respectively. With the appropriate choice of metallocene catalyst, the polymer formed shows narrow molecular weight distribution (Mw/Mn∼2), and the polymer molecular weight is inversely proportional to the molar ratio of [CT agent]/[α-olefin]. In turn, the terminal borane group is very versatile in interconversion to various polar groups. More importantly, it can be quantitatively transformed to a living radical initiator for chain extension reaction with functional monomers. On the other hand, the terminal styrenic group was then selectively metallated and transformed to a stable polymeric anion for living anionic polymerization. The overall diblock co-polymer process resembles a transformation reaction from metallocene-mediated α-olefin polymerization to a living free radical or a living anionic polymerization of functional monomers.

This chapter discusses a facile and clean method to prepare maleic-anhydride (MA)-modified polyolefins with well-defined molecular structure offered by the reactive copolymer approach. The chemistry is benefited by metallocene technology that results in reactive copolymers with narrow molecular weight and composition distributions, as well as controlling the concentration and location of reactive co-monomer incorporation. The reactive groups in the copolymer provide the selective sites for MA modification reaction. Such a reaction minimizes the undesirable side reaction in the polyolefin backbone and preserves its important properties. The chapter discusses the well-defined MA-terminated polyolefins, especially polypropylene (PP) with controllable PP molecular weight and MA units at the polymer chain end. The new PP-MA block copolymers provide detailed information about the effects of PP-MA structure to the compatibility of the reactive PP/nylon blends. The new MA-modified polymers with various molecular structures also offer an excellent opportunity to prepare other segmental polymers. An example presented is the new long-chain branched polypropylene (LCBPP), which has a relatively well-defined molecular structure.

This chapter discusses the direct copolymerization reactions of α-olefins and functional monomers, such as oxygen, nitrogen, and chlorine. Two general research approaches, including protecting the polar functional groups and using less oxophilic late transition metal catalysts, have been described. The combination of both approaches usually results in the best performance, especially in Ziegler-Natta and metallocene catalysis. In addition to some concerns, such as (1) the cost of protection and deprotection processes and (2) the removal of impurities, it is very important to preserve some important polyolefin properties, such as crystallinity, melting temperature, and processibility during the functionalization reaction. The major applications of functional polyolefins are in the roles of interfacial agents to promote adhesion and compatibility among polyolefin and other polar materials in polyolefin blends and composites. The chapter discusses the advantages and disadvantages of both the protective and less oxophilic late transition metal catalyst approaches. These approaches depend on the selection between two co-existing acid-base interactions between a catalyst and a functional monomer containing two bases. The ideal reaction environment is a facile acid-base interaction between an active site and the Π-electrons of an α-olefin unit, and no acid-base interaction between an active site and a lone pair of electrons in a hetero-atom (O, N, X) of a functional group.

This chapter focuses on the reactive polyolefin containing borane groups, and discusses its advantages. The borane approach provides a very effective method for the functionalization of polyolefin with well-controlled polymer structure. This general method can be applied to all polyolefins and to most functional groups. This process is particularly suitable in the preparation of hydroxylated polymers because of the quantitative conversion under mild reaction conditions. In direct polymerization, the borane containing α-olefins behaves like α-olefins and can be effectively incorporated into polyolefin structures. This facile chemistry is because of a unique combination of the stability of borane moiety to transition metal catalysts, the solubility of borane compounds in the hydrocarbon solvents used in transition metal polymerizations, and advances in metallocene catalysis that allow the effective incorporation of high monomers. In post-polymerization, the hydroboration reactions are very effective because of the excellent reactivity of boron hydride to olefinic units in the unsaturated polyolefin, and the good solubility of borane compounds in the hydrocarbon solvents used in the reactions.

This chapter focuses on the development of a versatile method to prepare functional polyolefin graft copolymers having relatively well-defined molecular structures. The chemistry is based on reactive polyolefin copolymers containing comonomer units, such as borane monomers, p-methylstyrene, and divinylbenzene. The reactive co-monomers can be very effectively incorporated into polyolefins, with narrow molecular weight and composition distributions by using metallocene technology. The pendent reactive groups, located along the polyolefin backbone, are very effective in engaging the subsequent graft polymerizations. The chapter presents an example of divinylbenzene that shows good reactivity in many subsequent polymerization mechanisms. This graft technique benefits greatly from the simplicity of its reaction process. Many functional polyolefin graft copolymers have been prepared and reported. Most of the functional polyolefin graft copolymers show good interfacial activities and improved morphology and adhesion between micro-domain structures. Improved mechanical properties of polyolefin blends and composites have also been presented in the chapter.

This chapter focuses on the polymerization behaviors of both boron and silane functional groups of polyolefins using early transition metal catalysts. The direct polymerization of a functional monomer by early transition metal catalysts is limited to a few monomers containing hetero-atoms having Lewis acid or neutral states and forming covalent carbon hetero-atom bonds. Borane and silane groups exhibit stability to catalyst and solubility in hydrocarbon media. The chapter discusses the applications of these reactive polyolefins, especially the borane-containing polymers. Borane monomers behave like high α-olefins, both in terms of their reactivity and the molecular structure of the resulting polymers. The silane groups in polyolefins can serve as the crosslinking agent. However, they are not polar enough to greatly affect the polymer properties. Borane groups can be transformed to a remarkable variety of functionalities, and also serve as initiators in the preparation of graft and block copolymers.

This chapter discusses the functionalization of polyolefin via unsaturated polyolefin, which offers a chemical route. With a proper choice of the unsaturation moiety and functionalization reaction, it is possible to prepare the desired functional polyolefin with a well-controlled molecular structure. The crucial link is the preparation of an unsaturated polymer with facile unsaturation moieties. The advance of metallocene technology provides the essential solution to empower this chemical approach. With the designed metallocene catalysts, most diene monomers can be effectively incorporated into polyolefin without causing the undesirable branching and crosslinking side reactions. Among them, divinylbenzene (DVB) is well-known to produce crosslinked polymer products in all other polymerization processes. The incorporated DVB units resemble the styrene monomer and are very facile in many reactions. The pendent styrene units can not only be converted to functional groups, but can also engage in other polymerization reactions to form graft copolymers containing a polyolefin backbone and several functional polymer side chains.

This introductory chapter provides an introduction to polyolefins and deals with its development and future prospects. Polyolefins are the most widely used commercial polymers because of their excellent combination of chemical and physical properties along with low cost, superior processibility, and good recyclability. By controlling crystallinity and molecular weight, polyolefins with a wide range of thermal and mechanical properties have been produced for wide range of commercial applications. The chapter provides an overview of the key components and steps in the coordination polymerization. This book captures some of the most important recent advances in the polyolefins, with the emphasis on functionalization approaches and an understanding of their scope and limitations.

This chapter describes five methods of preparing polyolefin diblock copolymers containing polyolefin and functional polymer segments: living Ziegler-Natta polymerization, transformation reaction from Ziegler-Natta to living free radical polymerization, transformation from Ziegler-Natta to living anionic polymerization, transformation reaction from anionic to Ziegler-Natta polymerization, and coupling reaction between two polymers. Diblock copolymer is the most effective interfacial agent in polymer blends and composites. Only a small quantity of a suitable diblock copolymer is needed to change the incompatible binary blends to uniform microphase morphology with strong interfacial adhesion. Most methods of preparing polyolefin diblock copolymers result in products with an intimate mixture of homopolymers and perhaps some diblock copolymer. However, some methods offer simple reaction processes and produce polyolefin diblock copolymers with a broad range of copolymer composition and well-designed molecular structure. The chapter concludes that the living Ziegler-Natta polymerization is mostly useful for the preparation of polyethylene diblock copolymers because of the limitation of applicable catalyst systems and reaction conditions.

This chapter summarizes three general methods used in the preparation of polyolefins with a terminal functional group. They are based on living transition metal coordination polymerization, in situ chain transfer reaction during transition metal coordination polymerization, and chemical modification of the polymer having an unsaturated chain end. The combination of metallocene catalysis and in situ chain transfer reaction is the most effective and convenient route. Chemistry can be easily extended to many polyolefin structures, including copolymers and terpolymers. This drop-in technology only needs minor modifications of current commercial polymerization processes. The chapter reveals that it would be convenient and beneficial to replace the current hydrogen chain transfer agent with borane or p-methylstyrene (p-MS)/H 2 chain transfer agents. Such a process not only allows the control of polymer molecular weight and chain-end saturation, it also provides a reactive functional group at the polymer chain end for further reactions. The chapter further mentions that living polymerization is a very expensive process from the commercial viewpoint. One catalyst site can only produce one polymer chain.

This chapter summarizes the current commercial method of a post-polymerization approach involving chemical modifications of the preformed polyolefin. Chemical modification of the existing commercial polymers presents an alternative to achieving the functionalization of polymers without the development of completely new polymerization processes. The approach circumvents the difficulties of catalyst poisoning by functional groups during the polymerization process. The modification reaction only incorporates the desirable functional groups into the polymer chain without changing the polymer structure and properties, such as molecular weight, melting temperature, and processability. The chapter discusses the basic chemistry of the free radical activation mechanism and associated free radical reactions. Many high-energy processes were applied in the hydrogen abstraction reaction of polyolefin. Radiation and plasma are commonly used in surface modifications of polymer films and membranes, and thermal process with external peroxide is commonly used in polymer bulk modifications. The chapter also summarizes the commercial applications of bulk and surface modifications.

This chapter provides a global view of the functionalization approaches of Polyolefins and discusses their scope and limitations. It illustrates three approaches to the functionalization of polyolefins: (1) direct copolymerization of α-olefin with functional monomer, (2) chemical modification of the preformed polymer, and (3) a reactive copolymer approach, incorporating reactive co-monomers that can be selectively and effectively interconverted to functional groups. The chapter presents some fundamental chemical difficulties in the direct copolymerization. The combination of the inert nature of polyolefin and a very short reaction causes great difficulties in controlling polymer composition and structure. The most frequently used free radical functionalization reactions that are usually accompanied with many undesirable side reactions and byproducts are discussed. The reactive copolymer approach has benefited greatly from metallocene technology. Several new reactive co-monomers have been effectively incorporated into polyolefins with narrow molecular weight and composition distributions. This approach has opened up the opportunity to prepare a broad range of new functional polyolefins with compositions and structures that would be very difficult to prepare by other methods.

This chapter discusses a reactive comonomer, p-methylstyrene (p-MS) that can be effectively incorporated into polyolefins by transition metal catalysts and can be subsequently interconverted to various desirable functional groups, such as -OH, -NH2, -COOH, anhydride, and halides. The reactive groups can be effectively transformed to stable anionic initiators for living anionic graft-from polymerization reactions. The resulting graft copolymers, containing a polyolefin backbone and several well-defined functional polymer side chains, offer not only a high concentration of functional groups, but also preserve the desirable polyolefin properties, such as crystallinity, melting point, and glass transition temperature. The chapter further discusses the major advantages of p-MS, such as its commercial availability, easy incorporation into polyolefins, and versatility in the functionalization chemistry under various reaction mechanisms including free radical, cationic, and anionic processes. The preparation of p-MS-containing polyolefin copolymers has been greatly enhanced by the metallocene technology. The well-defined metallocene catalyst with constrained ligand geometry, having a spatially opened catalytic site, allows the effective incorporation of large co-monomers.

In our earlier work, we have demonstrated that the high- energy electron irradiation modifies (VDF-TrFE) copolymers from a normal ferroelectric to a relaxor ferroelectric with high electromechanical response. Here, we present two approaches we are taking recently. One is to explore the non-irradiation approach to modify the PVDF-based material to achieve high electromechanical response. A ter-monomer (HFP and CTFE are used here) with a relative large size is added to the copolymer to act as modifiers. The electromechanical and dielectric properties in the terpolymers seem to be similar to those in irradiated copolymers. The other approach addresses the fundamental issue of the low dielectric constant in the currently available electroactive polymers. By making use of composite approach and ultra-high dielectric constant in CuPc, a polymeric composite with very high dielectric constant but the elastic modulus similar to polymer has been demonstrated. The preliminary results indicate that the polymer composite has the potential to generate high strain under much lower field. In parallel to the material development, we investigated device performance based on the irradiated copolymers. The performance of irradiated copolymer multilayers with a thickness up to 1 mm was characterized. The design and device performance of a flextensional actuator fabricated from the irradiated copolymer multiplayer are presented. The flextensional actuator, whose resonance frequency is at a frequency of a few kHz to more than 10 kHz, exhibits more than 1 mm displacement and high force output, which are attractive for many applications.

This paper discusses a new ferroelectric polymer with high dielectric constant (>50 at 1K-1M Hz) and large electrostrictive response (~5%) at ambient temperature, which is based on a processable semicrystalline terpolymer comprising vinylidene difluoride (VDF), trifluoroethylene (TrFE), and chlorotrifluoroethylene (CTFE). This VDF/TrFE/CTFE terpolymer was prepared by a combination of a borane/oxygen initiator and bulk polymerization process at ambient temperature. The control of monomer addition afforts the terpolymers with high molecular weight and relatively narrow molecular weight and composition distributions. The incorporated bulky CTFE units homogeneously distributed along the polymer chain seem to reduce the thickness of ferroelectric crystalline domains without destroying the overall crystallinity. This nano-size semicrystalline morphology results in the reduction of ferroelectric-paraelectric (F-P) phase transition to near ambient temperature with a very small energy barrier. Some terpolymers exhibited common ferroelectric relaxor behaviors with a broad dielectric peak that shifted toward higher temperatures as the frequency increased, and a slim polarization hysteresis loop at near the dielectric peak (around ambient temperature) that gradually evolved into a normal ferroelectric polarization hysteresis loop with reduced temperature.

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