The statistical anionic copolymerization of styrene (S) with 1,3-dienes with lithium counterion in apolar solvents is commonly used to synthesize “tapered” block copolymers, enabling the con-trol of the phase behavior by adjusting the order-disorder transition temperature. Lewis-base modifiers (ethers, amines) have been used to “randomize” the copolymerization, also affecting the regio- and stereostructure of the polydiene comonomer segments.
Recently, biobased terpene derivates like β-myrcene or β-farnesene have come into the focus of interest. These building units can be obtained directly from natural feedstocks, by enzymatic conversion of biomass or indirectly by chemical transformation processes.
The effect ethers and alkoxides on the copolymerization kinetics of styrene with isoprene, myrcene and farnesene, respectively, and the gradient of the resulting copolymers were systemat-ically investigated by increasing the [modifier]/[Li] ratio. In situ near-infrared (NIR) kinetics ren-dered reactivity ratios. Corresponding changes in the copolymer composition profile up to a complete inversion are evident in thermal properties and morphologies. Although all copolymers possess the same comonomer composition (57%vol PS-units) SAXS and TEM give evidence of a wide variation in bulk morphologies depending on the gradient profile.
Nopadiene (Nopa) is a new terpene-based diene monomer. PNopa obtained by anionic polymerization in cyclohexane or methyl t-butyl ether (MTBE) has a surprisingly high Tg of 160 °C, potentially replacing styrene. Thus, ABA block copolymers with other dienes are thermo-plastic elastomers (TPEs). Based on favorable reactivity ratios the statistical copolymerization of Nopa and farnesene using a difunctional initiator in MTBE renders TPEs within just one single step.

Molybdenum alkylidyne N-heterocyclic carbene (NHC) complexes of the type [Mo(C-p-C6H4Y)(OC(R)(CF3)2)2 (L)(NHC)][B(ArF)4] (Y = OMe, NO2; R = CH3, CF3; L = none, pivalonitrile, tetrahydrofuran; NHC = 1,3-dimesitylimidazol-2-ylidene, 1,3-dimesityl-3,4-dihydroimidazol-2-ylidene, 1,3-dimesityl-3,4-dichloroimidazol-2-ylidene (IMesCl2), 1,3-diisopropylimidazol-2-ylidene; B(ArF)4- = tetrakis(3,5-bis(trifluoromethyl)phen-1-yl)borate) were used in the ring expansion metathesis polymerization (REMP) of cyclic olefins. With cis-cyclooctene (cCOE) cyclic, low molecular weight oligomers were obtained at low monomer concentration and the exclusive cyclic nature of the polymer was confirmed by matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry. High-molecular weight cyclic poly(cCOE) became available at high monomer concentration. Also, post-REMP allowed for converting low-molecular weight cyclic poly(cCOE) into high molecular weight cyclic poly(cCOE). Tailored catalysts together with suitable additives offered access to the stereoselective REMP of functional norbornenes providing functional cis-isotactic (cis-it), cis-syndiotactic (cis-st) and trans-it poly(norbornene)s with up to 99 % stereoselectivity. Mechanistic details supported by density functional theory calculations are outlined.
A cationic molybdenum alkylidyne NHC complex selectively immobilized inside the pores of ordered mesoporous silica (OMS) with pore diameters of 66Å and 28Å, respectively, also allows the REMP of cyclic olefins to yield cyclic polymers. Application of a strong confinement effect offers access to low molecular weight cyclic polymers even at high monomer concentration in the REMP of cCOE, 1,5-cyclooctadiene (COD), (+)-2,3-endo,exo-dicarbomethoxynorborn-5-ene ((+)-DCMNBE), and 2 methyl-2-phenylcycloprop-1-ene (MPCP). The exclusive formation of cyclic polymers was again demonstrated by MALDI-TOF mass spectrometry. Confinement also influences stereoselectivity resulting in a pronounced increase in Z-selectivity and in an increased cis-syndiospecificity.

Sustainable polymers continue to generate interest.¹ In particular, aliphatic polyesters can be degradable under mild conditions and biocompatible, which makes them relevant for medical applications. Copolymerization of one or more monomers broadens the window or accessible polymer properties (e.g. thermal, mechanical). A significant challenge in the field of polymer synthesis is the synthesis of sequence-controlled block copolymers. The development of self-switchable polymerizations, whereby a catalyst can select between different polymerization cycles depending on whether a monomer is present or absent in the reaction mixture or the identity of the polymer chain end, has been used to prepare a range of copolymers incorporating polycarbonates.² Switchable polymerization is very challenging when all monomers incorporate the same functional group.
We have developed a selective and self-switchable ring-opening polymerization ROP system to prepare block copolymers of the form (AB)x(BC)y from three different cyclic ester monomers (lactide (LA), β-butyrolactone (β-BL) and ε-caprolactone (ε-CL)) using an yttrium complex.³ The catalyst has previously been shown to copolymerize lactide (LA) and β-butyrolactone (β-BL) in a selective manner.⁴ Each polymer block is composed of units of two monomers but completely excludes the other monomer. The switch from formation of the AB block to the BC block is determined by whether LA is present, and not by relative monomer concentrations. It is possible to prepare a range of copolymers with different block lengths and compositions, and therefore different properties, by manipulating the initial monomer feed.

We have developed synthetic approaches for the preparation of amphiphilic miktoarm star block copolymers to investigate how the architecture of the block copolymers influences their self-assembly. We prepared AB₂-type amphiphilic miktoarm stars consisting of one hydrophilic arm (A) and two hydrophobic arms (B) to mimic the structure of lipids. We used a heterofunctional core as a multifunctional initiator to prepare the miktoarm stars. The hydroxyl group of the initiator was used to initiate the ring-opening polymerization (ROP) of trimethylene carbonate (TMC) or propylene oxide (PO) to form the hydrophobic arms B, while the hydrophilic block A was prepared by ROP of sarcosine N-carboxyanhydride using the amine group for ROP initiation. To selectively initiate ROP, the amine group of the heterofunctional core was protected with a suitable protecting group. While carbamate-based protecting groups such as Boc and Cbz are compatible with the catalytic systems used for TMC polymerization, the incorporation of primary amine functionality into polyethers is more challenging due to the harsher conditions usually employed for ROP of epoxides. To overcome this challenge, we used a Lewis acid-excess two-component organocatalytic system that triggers efficient anionic ROP of epoxides while preserving the integrity of the carbamate protection.¹ Despite the higher intrinsic acidity of the carbamate group compared to the hydroxyl group, it is not competitive in both deprotonation and ring-opening steps. This is due to the acidity-reversing effect of the catalyst, which allows site-specific ethoxylation to proceed exclusively from the hydroxyl group.

Polyolefins share over 60 % of total worldwide production as they exhibit good chemical resistance, mechanical properties, and low cost of the production at the same time. However, their further utilization is rather limited due to their low surface energy that reflects in incompatibility with other polymers, lack of adhesion to other materials as well as limited paint- and printability. [1] The application range can be easily extended by their functionalization. [2–4] While post-polymerization functionalization is the only commercialized approach for polypropylene-based functionalized polyolefins, in-reactor functionalization polymerization receives increasing interest of both academia and industry as it allows to precisely tune products’ properties. [4] However, despite extensive research the question whether such randomly functionalized polyolefins can be produced in a commercially viable process remains unanswered.
Herein, we describe the challenges that must be overcome to produce randomly hydroxyl-functionalized polypropylene copolymers in an efficient and scalable manner using aluminum alkyl-passivated alkenols as functional comonomers. [5] The impact of the type of (i) the functional comonomer and (ii) the passivating agent on the catalytic activity and incorporation efficiency is elucidated. Moreover, deep insight into the catalytic process and catalyst poisoning revealed phenomenon that were never described before. The high nuclearity of the aluminum alkyl-passivated functional comonomers proved to be a major roadblock for a commercially viable process, but with a simple elegant trick this challenge could be overcome.

Butadiene and isoprene are highly significant conjugated diene monomers, widely used in the rubber and tire industry.[1] Recently, controlled radical polymerization of dienes has received growing academic and industrial interest. Reversible addition-fragmentation chain transfer (RAFT) polymerization offers significant advantages over conventional diene polymerization, particularly in achieving precise control over molecular weight, enabling the incorporation variety of monomers, and facilitating the functionalization of end groups. These capabilities enable the attainment of desired physical and mechanical properties of polymeric materials, ultimately enhancing the performance and quality of rubber.[2, 3]
A major challenge in the RAFT polymerization of dienes is achieving high molecular weights comparable to those obtained through conventional free-radical or ionic polymerization methods. Current solution-phase RAFT polymerization of dienes typically yields molecular weights of about 30,000 g mol⁻¹.[1, 2] Such low molecular weight polymers can find use as liquid polymers. However, as high molecular weight has marked impact on material properties, it is advantageous for broad industrial applications.
In this work, a novel approach is explored to achieve higher molecular weights by utilizing bifunctional RAFT agents. The strategy involves leveraging the functionality of end groups to multiply the molecular weight of the resulting polymers. This can be accomplished by increasing the initiator concentration during polymerization, thereby promoting recombination termination mechanisms to couple diene polymer chains. Another method involves a post-polymerization reaction of the RAFT functionalized polymer.