Chain-end Functional Groups Research Articles

Facile and efficient in-situ end-functionalization of neodymium-based polybutadiene by isocyanate via a coordinative chain transfer polymerization strategy

Tapping facile and efficient strategies for in-situ end-functionalization of polydiene elastomers has been pursued for scientists for decades. This has been especially prominent for Ziegler-Natta type catalytic systems, because they hold great potential for future large-scale industrializations. In this report, through using a newly emerged method of coordinative chain transfer polymerization (CCTP), we introduce a simple and convenient method to efficiently end-functionalize neodymium-based polybutadienes by in-situ addition of isocyanate or isothiocyanate compounds. These two types of substrates performed high reactivities with η1-allyl-Al capped polybutadienyl chain-ends, that were generated from fast and reversible chain transfer reactions, giving high functionalization efficiencies (up to 97.1 %). The high functionalization efficiencies were also applicable to isocyanate or isothiocyanate substrates bearing different functionalities, showing a broad scope capability. Moreover, such a functionalization process was not influenced by the viscosities of the reaction system, as revealed from the kinetic studies that linear relationship was obtained between Mns and various [BD]/[Nd] ratios, implying again the high reactivities of the isocyanate or isothiocyanate compounds. Due to the incorporation of amide or thioamide functional group into the chain-ends, the corresponding polybutadienes showed much improved surface properties and performed higher mechanical properties than unfunctionalized counterparts for raw rubber matrix. Regarding the vulcanizate, chain-end functional groups could also result in much improved filler dispersion and stronger interaction between rubber and filler particles, which eventually gave rise to better mechanical properties, inducing higher tensile strength, more toughness, and greater tear strength.

Oligoimide-Mediated Graphene Oxide-Epoxy Nanocomposites with Enhanced Thermal Conductivity and Mechanical Properties.

The current study reports the preparation of thermally conductive polymeric nanocomposites. For this purpose, two epoxy-based nanocomposites were prepared by dispersing a different type of functionalized graphene oxide (GO) nanofiller in each series. Both these GO nanofillers were functionalized by covalently bonding oligoimide chains on their surfaces. In one series, these oligoimide chains were prepared by reaction of 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) with a diamine 4,4′-methylenedianiline (MDA). While in the other case, BTDA was reacted with N,N′-[((propane-2,2-diylbis(4,1-phenylene))bis(oxy))bis(4,1-phenylene)]bis(4-aminobenzamide) (BDM) to mount oligoimide chains on the surface of GO. Both types of oligoimide chains have amino groups as chain-end functional groups. These modified GO nanofillers were added to the epoxy matrices separately to prepare their respective nanocomposites (MDA-B-GO-epoxy nanocomposites and BDM-B-GO-epoxy nanocomposites). The chain-end amino groups of oligoimide chains reacted with the epoxy ring developing a covalent bonding between oligoimide chains of GO and the epoxy matrix. Moreover, these oligoimide chains prevented the agglomeration of GO by acting as spacer groups leading to the uniform dispersion of GO in the epoxy matrix. Various analytical techniques were used to examine the attachment of oligoimide chains to the GO surface, and to examine the morphology, curing potential, mechanical strength, thermal stability, and thermal conductivity of the prepared nanocomposites. We demonstrated that the thermal conductivity of MDA-B-GO-epoxy nanocomposites increased by 52% and an increase of 56% was observed in BDM-B-GO-epoxy nanocomposites. Similarly, a significant improvement was observed in the mechanical strength and thermal stability of both types of nanocomposites.

Thermoresponsive Polypeptoids.

Stimuli-responsive polymers have been widely studied in many applications such as biomedicine, nanotechnology, and catalysis. Temperature is one of the most commonly used external triggers, which can be highly controlled with excellent reversibility. Thermoresponsive polymers exhibiting a reversible phase transition in a controlled manner to temperature are a promising class of smart polymers that have been widely studied. The phase transition behavior can be tuned by polymer architectures, chain-end, and various functional groups. Particularly, thermoresponsive polypeptoid is a type of promising material that has drawn growing interest because of its excellent biocompatibility, biodegradability, and bioactivity. This paper summarizes the recent advances of thermoresponsive polypeptoids, including the synthetic methods and functional groups as well as their applications.

Orthogonally "Clickable" Biodegradable Nanofibers: Tailoring Biomaterials for Specific Protein Immobilization.

Multifunctionalizable polymeric nanofibers can be tailored for various biomedical applications by selective conjugation of small molecules and bioactive ligands. This study reports the design, synthesis, and application of novel biodegradable polyester-based nanofibers bearing metal-free “clickable” handles. Polylactide-based polymers were synthesized using organo-catalyzed ring-opening polymerization to contain “clickable” chain-end functional groups that specifically react through radical or nucleophilic thiol–ene reactions. A furan-protected maleimide-containing hydroxyl-bearing initiator yielded polymers containing strained oxanorbornene unit at their chain end. In addition, postpolymerization thermal treatment provides maleimide end group-containing polymers. Solution electrospinning method was utilized to obtain bead-free nanofibers. Efficient conjugation on these nanofibers was demonstrated using metal-free conjugation reactions. It was observed that polylactide nanofibers undergo extensive biofouling, which limits their possible utilization for specific biomolecular immobilization. To alleviate this problem, polymers were modified to contain two orthogonally reactive functional groups, namely, the oxanorbornene unit and an azide group at their chain ends. The former reactive handle was used for conjugation of poly(ethylene glycol) chains to impart hydrophilicity and thus an antibiofouling ability, whereas the azide group undergoes strain-promoted azide–alkyne cycloaddition to install a protein-binding ligand such as biotin. These nanofibers were able to specifically immobilize the protein streptavidin with minimal nonspecific adsorption.

Developing a nontoxic and biocompatible polymeric self-assembly by using RAFT methodology for biomedical application

The amphiphilic block copolymer poly(N-vinylpyrrolidone)-b-poly(N-vinylcarbazole) (PVP-b-PVK) was synthesized by reversible-deactivation radical polymerization (RDRP)using reversible addition-fragmentation chain transfer (RAFT) methodology by new chain transfer agent (CTA) i.e. benzyl piperidine dithiocarbamate (BPDC). The pseudo-first-order kinetics and linear evolution of the molar mass with N-vinylpyrrolidone (NVP) conversion were obtained with the molar mass dispersity (Ð) 1.30–1.41 in toluene. 1H NMR spectrum indicates the presence of chain-end functional groups on homopolymer and block copolymer. The above block copolymer get self-assembled and form micelles in the aqueous medium, the size of micelles is characterized by 1H NMR, transmission electron micrographs (TEM) and dynamic laser light scattering (DLS) analyses, and critical micelles concentration (CMC) was determined by UV–vis spectroscopy. Trypan blue exclusion and MTT assay were done to ensure the cytotoxic effect of PVP-b-PVK on different types of normal cells (thymocytes, splenocytes and macrophage), and no cytotoxic effect was shown by block copolymer on cells, while observed biocompatibility with cells was 200 mg/mL. Further, the beads of block copolymer releases (65%) highly water-soluble levofloxacin drug up to 8 h in a controlled manner at pH 7.4 (37 ± 0.2 °C), while loading of levofloxacin drug was 62% (w/w).

Chain-length dependent interfacial immunoreaction kinetics on self-assembled monolayers revealed by surface-enhanced infrared absorption spectroscopy

Self-assembled monolayer (SAM) has been extensively applied as ideal interface layer for construction of biosensors. Its chain length and end functional groups determine the physical and chemical properties of the modified surfaces, which will affect the performance of constructed biosensors. Herein, we studied the influence of chain length of n-alkanethiols SAMs on the immunoreaction kinetics employing attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS). Antibody (rabbit immunoglobulin) is assembled on carboxyl terminated SAMs of n-alkanethiols with different chain lengths (n = 3, 6, 11, 16). The whole fabrication steps of the immunoassay can be monitored in situ by the ATR-SEIRAS. From the time-dependent SEIRA spectra, the interfacial immunoreaction kinetics between the immobilized antibody and antigen (goat anti-rabbit immunoglobulin) can be evaluated. We found that the immunoreaction became faster with increasing the chain length of SAMs. This chain length dependent kinetics might be attributed to different orientations of the assembled antibody caused by different packing densities of SAMs. The present research offers a sensing platform to evaluate immunoassay kinetics and provides fundamentals for construction of immunoassay with high performance.

Facile synthesis of low-polydispersity block copolymer vesicles by azide-zwitterion cycloaddition

ABSTRACTPolycaprolactone with azide (PCL-N3) and polyethylene glycol with α,β-unsaturated ester (maPEG) as chain-end functional group were synthesized, respectively. Then, facile synthesis of polycaprolactone-block-polyethylene glycol (PCL-b-PEG) amphiphilic copolymer by azide-zwitterion cycloaddition of PCL-N3 and maPEG, as the first example, was reported. The self-assembly of this amphiphilic copolymer was carried out in deionized water, and then the formation of vesicles was proven by the result of transmission electron microscope (TEM). Grainsize analyzer suggested that the diameter of the vesicles is 305 nm in average and the polydispersity of the vesicles is 0.128. The azide-zwitterion cycloaddition provides a powerful method for the post-functionalization of α,β-unsaturated ester or azide end-functionalized polymers.

Dithiobenzoic copper(II): A novel, facile, and stable mediating agent combining ATRP and RAFT features for reversible deactivation radical polymerization of methacrylates

Novel, facile, and stable mediating agent (dithiobenzoic copper(II)) combining atom transfer radical polymerization (ATRP) and reversible addition fragmentation transfer (RAFT) characteristics was firstly designed by replacing the halogen of ATRP metal catalyst with thiocarbonyl carboxylic group of RAFT agent. As two kinds of mediating agents (ATRP activator and RAFT agent) may be formed in situ during the polymerization process, the polymerization of various methacrylates can be controlled in presence of a high molar ratio of radical initiator to catalyst. Furthermore, the resultant polymer possessed dithiobenzoate chain-end functional group, which was confirmed by IH NMR analyses and chain-extension reaction.

Nitroxide-Mediated Polymerization of Vinyl Chloride at Low Temperature: Kinetic and Computational Studies

The synthesis of poly(vinyl chloride) (PVC) by nitroxide-mediated polymerization (NMP) using the SG1-based BlocBuilder alkoxyamine at low temperature (30 and 42 °C) is reported. The reaction system was studied regarding the nature of the solvent, the monomer-to-solvent ratio, the polymerization temperature, and the target molecular weight. First-order kinetics and linear evolutions of the molecular weight with vinyl chloride (VC) conversion were obtained in dichloromethane (DCM) and dimethyl sulfoxide (DMSO) together with decreasing dispersities (Đ) down to 1.59–1.47. The resulting PVC was fully characterized by 1H nuclear magnetic resonance spectroscopy (1H NMR), 31P NMR, and size exclusion chromatography (SEC). The 1H NMR and 31P NMR revealed the existence of very small content of structural defects and the presence of chain-end functional groups (∼91% SG1 chain-end functionality). Chain extension experiments were performed with VC, methyl methacrylate (MMA), and a mixture of monomers (90% of MMA and 10% of styrene (S)) and confirmed the “livingness” of the PVC-SG1 macroinitiators, giving access to different PVC-based block copolymers. High level ab initio molecular orbital calculations suggested that the C–O bond in the PVC-SG1 alkoxyamine is too strong to mediate the NMP of VC by simple “classic” activation–deactivation equilibrium and is possibly being mediated by a SG1-mediated dehydrochlorination mechanism. The results presented in this study established a new route to afford a wide range of new complex macrostructures based on PVC segments.

Normal-phase (temperature gradient) interaction chromatography – A powerful tool for the characterisation of high molecular weight chain-end functionalised polymers

We report here, for the first time, quantitative analysis of end-group functionalisation and the extent of end-group modification of polymers with molar mass up to 200,000gmol−1, using a combination of isothermal and temperature gradient interaction chromatography. At such high molecular weights, other common analytical techniques such as MALDI-ToF-MS and NMR spectroscopy are simply unable to offer any quantitative insight into the end-group functionality of polymers. Thus, normal phase isothermal interaction chromatography (NP-IIC) has been used to characterise a series of polystyrene samples, with identical molar mass (c. 90,000gmol−1), each carrying a single chain-end functionality of varying polarity, introduced via a series of end-group transformation reactions – from silyl-protected alcohol→primary alcohol→alkyl bromide. It is shown that the polarity of the functional group dictates the elution volume of the polymers and that NP-IIC could be used to monitor the quantitative end-group transformation. Thus, rather than estimating the success of the transformation reaction from the very small peaks observed in 1H NMR spectra, NP-IIC gives clear chromatographic peaks, whose retention volumes change dramatically only as a consequence of each new chain-end functional group. We also describe the analysis, by a combination of normal phase isothermal and temperature gradient interaction chromatography, of a series of linear polybutadiene samples of varying molar mass (28,000–200,000gmol−1) each carrying a single primary alcohol functionality at the chain-end. The primary alcohol functionality enabled the separation of functionalised and non-functionalised polymers, which eluted at different retention volumes despite identical molecular weights. It is all the more remarkable that complete (baseline) resolution can be achieved for two polymers with an identical molar mass (<200,000gmol−1), which differ only in that one sample is functionalised with a single primary alcohol group.

Occurrence, fluxes and sources of perfluoroalkyl substances with isomer analysis in the snow of northern China

In this study, perfluoroalkyl substances (PFASs) and the isomers of perfluorooctanoate (PFOA) and perfluorooctanesulfonate (PFOS) were analyzed in fresh snow samples collected from 19 cities in northern China, 2013. The levels of total PFASs in the snow samples were 33.5–229ng/L, suggesting heavy atmospheric pollution of PFASs in northern China. PFOA (9.08–107ng/L), PFOS (3.52–54.3ng/L), perfluoroheptanoate (PFHpA) (3.66–44.8ng/L), and perfluorohexanoate (PFHxA) (3.21–23.6ng/L) were predominant with a summed contribution of 82% to the total PFASs. The particulate matters (PMs) associated PFASs contributed 21.5–56.2% to the total PFASs in the snow, suggesting PMs are vital for the transport and deposition of airborne PFASs. Partitioning of PFASs between PM and dissolved phases was dependent on the carbon chain length and end functional groups. Isomer profiles of PFOA and PFOS in the snow were in agreement with the signature of the historical 3M electrochemical fluorination (ECF) products, suggesting that the ECF products were still produced and used in China. Further source analysis showed that the airborne PFASs in urban area were mainly due to direct release rather than degradation of their precursors.

Effect of styrene-butadiene rubber with different macrostructures and functional groups on the dispersion of silica in the compounds

In this study, the effects of high vinyl solution styrene-butadiene rubber (SSBR) containing different macrostructures and chain-end functional groups were investigated with respect to the dispersion of silica in the compounds. The microstructures and functional groups of three polymers were analyzed by using 1H nuclear magnetic resonance (NMR). According to the 1H NMR analysis, the star-shaped SSBR-E has a relatively higher numbers of ethoxy group in the polymer chain. All compounds showed good silica dispersion based on transmission electron microscopy (TEM) observation. According to analysis of the Payne effect, longer mixing times showed better dispersion of silica in the rubber compounds, and functional group differences in the SSBR also had an effect on the degree of silica dispersion that led to a decrease in storage modulus. In particular, the compound with star-shaped polymer containing ethoxy silyl groups showed the lowest storage modulus due to a higher number of functional groups compared to the other polymers. The abrasion resistance was closely related to the silica dispersion as well as the filler-rubber interaction. The abrasion loss decreased slightly when the mixing time was extended; however, this significantly decreased when the number of functional groups in the polymer chain was increased. Accordingly, the star-shaped polymer containing higher numbers of the functional group contributed to a better dispersion of silica in the compound. Mixing time was also considered as an important parameter to improve dispersion of silica and for reduction of silica flocculation in the rubber compounds.

Squaric Acid Mediated Synthesis and Biological Activity of a Library of Linear and Hyperbranched Poly(Glycerol)–Protein Conjugates

Polymer-protein conjugates generated from side chain functional synthetic polymers are attractive because they can be easily further modified with, for example, labeling groups or targeting ligands. The residue specific modification of proteins with side chain functional synthetic polymers using the traditional coupling strategies may be compromised due to the nonorthogonality of the side-chain and chain-end functional groups of the synthetic polymer, which may lead to side reactions. This study explores the feasibility of the squaric acid diethyl ester mediated coupling as an amine selective, hydroxyl tolerant, and hydrolysis insensitive route for the preparation of side-chain functional, hydroxyl-containing, polymer-protein conjugates. The hydroxyl side chain functional polymers selected for this study are a library of amine end-functional, linear, midfunctional, hyperbranched, and linear-block-hyperbranched polyglycerol (PG) copolymers. These synthetic polymers have been used to prepare a diverse library of BSA and lysozyme polymer conjugates. In addition to exploring the scope and limitations of the squaric acid diethylester-mediated coupling strategy, the use of the library of polyglycerol copolymers also allows to systematically study the influence of molecular weight and architecture of the synthetic polymer on the biological activity of the protein. Comparison of the activity of PG-lysozyme conjugates generated from relatively low molecular weight PG copolymers did not reveal any obvious structure-activity relationships. Evaluation of the activity of conjugates composed of PG copolymers with molecular weights of 10000 or 20000 g/mol, however, indicated significantly higher activities of conjugates prepared from midfunctional synthetic polymers as compared to linear polymers of similar molecular weight.

Reversible Addition–Fragmentation Chain Transfer Polymerization of Vinyl Chloride

Controlled/“living” radical polymerization (CLRP) of vinyl chloride (VC) via the reversible addition–fragmentation chain transfer (RAFT) process is reported for the first time. The cyanomethyl methyl(phenyl)carbamodithioate (CMPCD) was found to be an efficient RAFT agent enabling the CLRP polymerization of VC monomer under certain experimental conditions. Two different radical initiators, having very distinct half-life times at room temperature, were employed in this study. The kinetic studies of RAFT polymerization of VC show a linear increase of the molecular weight with the monomer conversion and the lowest polydispersity (PDI) ever reported for poly(vinyl chloride) (PVC) synthesized with CLRP method (PDI ∼ 1.4). The resulting PVC was fully characterized using the matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS), 1H nuclear magnetic resonance spectroscopy (1H NMR), and gel permeation chromatography (GPC) techniques. The 1H NMR and MALDI-TOF-MS analysis of PVC prepared via RAFT polymerization method have shown the absence of structural defects and the presence of chain-end functional groups. The “livingness” of the PVC was also confirmed by a successful reinitiation experiment. The suitability of the RAFT agent was also confirmed via high-level ab initio molecular orbital calculations.

Molecular dynamics simulation of the interface between self-assembled monolayers on Au(1 1 1) surface and epoxy resin

Two kinds of functionalized self-assembled alkanethiol monolayers (HS(CH 2) n OH and HS(CH 2) n NH 2, n = 1–17) were prepared on the Au(1 1 1) surface. The interface structures and interaction energies between S(CH 2) n X/Au(1 1 1) (X = OH, NH 2) and epoxy resin were studied by molecular dynamics methods. Moreover, the influence of chain lengths and end functional groups of thiols on the interfacial properties was also investigated. The results indicate that for the system of S(CH 2) n OH/Au(1 1 1) and epoxy, the interface energy increases firstly and then decreases gradually with the increase of chain length, and the energy reaches its minimum value when n = 11. Meanwhile, the interface of the S(CH 2) n NH 2/Au(1 1 1) and epoxy system is the most stable when n = 10. These results were compared with experiments, which prove that the simulation methods in this paper are advisable. The changes of structural parameters of the self-assembled monolayers (SAMs) after interacting with the epoxy indicate that there are strong interactions between the SAMs and epoxy resin. And the interface structures of the S(CH 2) n NH 2 and epoxy systems are more stable than those of the S(CH 2) n OH and epoxy ones.

Stability analysis and molecular simulation of nanoscale lubricant films with chain-end functional groups

In this article, the thermodynamic stability of ultrathin perfluoropolyether (PFPE) films were examined via experimentation and molecular simulation. Using measured surface energies of PFPE films and a virgin carbon overcoat, a mesoscopic model using the Gibbs free energy change of spreading PFPE films was developed, yielding a film stability diagram as a function of film thickness, surface polarity of the carbon overcoat, and molecular weight of the PFPEs. We predict that a lower PFPE molecular weight and a lower surface polarity of the carbon overcoat produce a less stable film. This stability analysis was enhanced with off-lattice Monte Carlo simulations, which were applied for the first time to examine PFPE film nanostructures. The simulation results produced oblate conformations for the PFPE molecules near the surface, layered polar endgroup orientations, and a rougher surface morphology for films with less stable conditions, as predicted by the Gibbs free energy model.

Stability Analysis of Ultra-Thin Lubricant Films with Chain-End Functional Groups

The thermodynamic stability of ultra-thin perfluoropolyether (PFPE) films is examined. The model used in this paper incorporates a layered structure due to polar interaction at the endgroups and provides the stability criteria as a function of film thickness, the surface/interfacial energies of PFPEs and substrates, and molecular weight. The surface energies of PFPEs were obtained from measured contact angles and separated into non-polar and polar components using Fowkes' method. The stability of PFPE films is examined via a diagram constructed from the measured surface energies of PFPEs and hydrogenated carbon substrate.

Synthesis of Propylene Diblock Copolymers via Metallocene and Borane Chemistry

A homogeneous metallocene Et(Ind)2ZrCl2 with MAO were used in the polymerization of polypropylene. This catalyst system produced a isotactic, and chain end unsaturated polypropylene. Borane was employed added to polypropylene to prepare a borane-containing polypropylene which can be transformed to hydroxyl-terminated polypropylene. Telechelic hydroxyl-terminated polypropylene, PPOH, can react with toluene diisocyanatc (TDI) to form a prepolymer-containing chain-end NCO functional group, PP-NCO. By using the resulting materials as macroactivators for anionic-ring-opening polymerization of caprolactam, a polypropylene-nylon 6 diblock copolymer was obtained. On the other hand, borane-containing polypropylene can react with oxygen to produce the free radicals located at the chain end on polypropylene. The free radical is effective initiator for the polymerization of methylmethacrylate to produce diblock copolymer of PP-b-PMMA. A diblock copolymer of PP-b-PU was also prepared. The block copolymers have been characterized by IR, NMR, and DSC. The diblock copolymer is a compatibilizer for various polypropylene blends with other polymers.

Hyperbranched Poly(ether ketones): Manipulation of Structure and Physical Properties

Hyperbranched poly(ether ketones), with a variety of chain end functional groups and controllable degrees of branching, are prepared by the polymerization of AB2, AB3, and AB4 monomers. It is found that the choice of A and B, or the incorporation of dendritic and linear units into the ABx monomer structure, dramatically affects the degree of branching. Depending on the structure of the monomer unit, degrees of branching ranging from 15 to 71% can be obtained. For determining the degree of branching for fluoro-terminated hyperbranched poly(ether ketones), a new technique based on 19F NMR has been developed. Evaluation of the physical properties of the hyperbranched poly(ether ketones) with different degrees of branching has shown that thermal properties are independent of macromolecular architecture but depend heavily on the nature of the chain end functional groups, with glass transition temperatures ranging from 97 to 290 °C. The solubility of the hyperbranched poly(ether ketones) is also shown to depend heavily on the nature of the chain ends, and by varying the chain ends, poly(ether ketones) soluble in either hexane or aqueous solutions could be obtained. The water-soluble derivatives were shown to act as unimolecular micelles.

Recent Advances in Anionic Synthesis of Functionalized Polymers

Abstract There has been growing interest and research on new synthetic methods for the preparation of well-defined polymers with in-chain and chain-end functional groups. These functional groups in polymers can participate in (a) reversible ionic association; (b) chain extension, branching or crosslinking reactions with polyfunctional reagents; (c) coupling and linking with reactive groups on other oligomer or polymer chains; and (d) initiation of polymerization of other monomers. It is noteworthy that the use of end-functionalized polybutadienes formed by reaction of poly(butadienyl)lithium with 4,4′-bis(diethylamino)-benzophenone has been reported to provide marked improvements in the wear and traction properties of tires. In order to exploit the unique potential of functionalized polymers, it is important to consider the scope and limitations of current functionalization methodology using anionic polymerization. Anionic polymerization approaches the goal of synthesizing polymers with predictable, well-defined structures in certain systems such as diene, styrene, methacrylate, and heterocyclic monomers, which proceed in the absence of chain termination and chain transfer reactions. These living polymerizations generate stable, anionic polymer chain ends when all of the monomer has been consumed. In principle, these anionic chain ends can react with a variety of electrophilic species to generate a diverse array of functional groups. Unfortunately, many of the reported functionalization reactions have not been well characterized. Another limitation of the use of specific electrophilic functionalization reactions is the necessity of developing, optimizing, and characterizing new procedures for each different functional group. Variables such as chain-end structure, solvent, temperature, concentration, stoichiometry, mode of addition of reagents, and polar additives can have dramatic effects on yield and product distributions. This review will first provide a critical overview of some recent developments in the use of specific functionalization reactions to prepare polymers labeled with carboxyl, hydroxyl, amino, and sulfonate end groups via alkyllithium-initiated polymerization methods. In addition, a recently developed methodology will be described which utilizes the addition reactions of organolithium compounds to substituted 1,1-diphenylethylenes as a general, quantitative functionalization reaction, independent of the specific functional group.