Laurolactam (LL) is polymerized in the bulk using strongly basic N-heterocyclic carbenes (NHCs) as initiators at temperatures of 180−200 °C to prepare the corresponding polyamide (PA 12). In-situ rheology of the polymerization progress reveals that an anionic mechanism is active, which is supported by the strong dependence of initiator activity on the basicity of the NHCs. GPC data and kinetic investigations show the process to be moderately controlled and fast, allowing high or quantitative yields in short polymerization times. Fifteen different NHC−CO 2 −adducts and NHC−metal complexes were used as thermally labile but room temperature stable NHC-precursors. Depending on the ring size and N-substituent, some of these protected NHCs allow forming a mixture of monomer and NHC-precursor that is suitable for long-term storage and readily polymerizable by simple heating. All polymerizations are executed without activator or other additives and thus represent a true one-component system for the production of PA 12. Finally, LL is copolymerized with εcaprolactam (ε-CLA). It is found that a copolymer with a considerable gradient is formed, with ε-CLA being incorporated preferentially at the onset of the polymerization.
Bisphenol A diglycidyl ether (BADGE)
is cured thermally using phthalic
acid anhydride (PhA) or hexahydrophthalic anhydride (HHPA) as hardener
in the presence of different protected N-heterocyclic
carbenes (NHCs), from which the catalytically active NHCs are generated
in situ upon heating. It is found that the curing reactions proceed
in a well-defined manner, delivering highly cross-linked, high-T
g-thermosets using low catalyst loadings (0.1–1
mol % of NHC precursor). The polymerizations can be conducted under
air without loss of activity, employing mild curing temperatures (120–160
°C) and short reaction times. By contrast, at room temperature,
polymerizations proceed only very slowly and the mixtures remain processable
for weeks, enabling formation of a true single-component composition
suitable for applications where large processing windows or storage
are required. The curing process was followed in situ by DSC as well
as by rheological measurements. On the basis of these observations,
the structure of the NHC precursor is correlated with its polymerization
activity with regard to latency, temperature profile and polymerization
kinetics. The robust and fully homogeneous system consisting of the
protected NHC, BADGE, and HHPA was successfully tuned both in terms
of activity and pot life by choosing the appropriate protected NHC
out of 12 different precatalysts. The most rapid polymerization was
effected by N,N′-bis(2,4-dimethoxyphenyl-)tetrahydropyrimidinium-2-carboxylate
(6-OMe-CO
2
), while a dimeric
zinc-based NHC-complex (6-Mes-ZnCl
2
) displayed the longest pot times.
Functional polyolefi ns are prepared from poly-CPE via ROMP by the action of a designed Rualkylidene initiator followed by quantitative hydroboration with 9-borabicyclo[3.3.1]nonane. The borylated polymers prepared in this way are then converted into hydroxy-, amino-, and silyloxy-functionalized polyolefi ns. With increasing polarity of the substituents, the glasstransition temperatures of the modifi ed polymers increase signifi cantly. Perhydrobrominated poly-CPE is prepared from poly-CPE and HBr and subjected to Cu(I)-mediated ATRP-based grafting to yield poly( tert -butyl acrylate)-grafted polyethylene (PE). The synthetic routes reported here present a straightforward access to functional and polar olefi ns.
A series of ZrIV and TiIV complexes containing the 6‐(2‐(diethylboryl)phenyl)pyridyl‐2‐yl motif are used in the methylalumoxane‐triggered copolymerization of ethylene (E) with norborn‐2‐ene (NBE). 13C NMR analyses reveal that vinyl insertion polymerization (VIP)‐derived poly(E)‐co‐poly(NBE) is obtained with pre‐catalysts 1–4 and 6, while pre‐catalyst 5 allows for the synthesis of a copolymer that contains both VIP‐ and ring‐opening metathesis polymerization (ROMP)‐derived structures. All the VIP‐derived poly(E)‐co‐poly(NBE) sequences show predominantly isolated NBE/alternating‐syndiotactic E‐NBE, as well as alternating‐isotactic E‐NBE sequences. The microstructure of the copolymers is correlated with the propensity of the pre‐catalysts to allow tandem ROMP‐VIP.
Microphase-separated lamellar block copolymers can be oriented perpendicular to a substrate. The application of this attractive configuration as a template for nanostructure fabrication requires additionally long-range in-plane alignment of the lamella, for which no simple procedures are available.Here we present a convenient solution to this problem by exploiting the combination of supramolecular liquid-crystalline ordering of the block copolymer in combination with PTFE rubbing technology. The mesogenic ligands incorporated in one of the blocks interact with the substrate and control the selfassembly, rendering a vertical orientation of the microdomains. In addition the vertical lamellae orient parallel to the friction-deposited PTFE layer leading to long-range lateral ordering, providing unique new possibilities for block copolymer nanotechnology.
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