FAQ

GENERAL INFORMATION

  • 1. What methylene malonates do you offer for sampling?

    Chemilian® products are monofunctional methylene malonates (monomers). These esters have the general formula below, where R groups are ethyl (Chemilian® M1000 XP), hexyl (Chemilian® L3000 XP) and cyclohexyl (Chemilian® H4000 XP). The homopolymer glass transition temperature (Tg) is -40°C for Chemilian® L3000 XP and 140°C  for Chemilian® H4000 XP. These monomers can be polymerized by anionic and free radical initiation. For further information, please refer to Chemilian® technical data sheets (TDS).

    Forza® B5200 XP is a multifunctional methylene malonate oligomer: it has more than one polymerizable vinyl group within the same molecule. We often refer to such compounds as “macromers.” Forza® B5200 XP macromer is obtained from 1,4-butanediol. Its generalized structure is shown below. This oligomer also polymerizes anionically and free radically and results in highly crosslinked polymer networks suitable for various applications including coatings, inks, adhesives, composites, microencapsulation, etc. For additional information, please refer to Forza® B5200 XP TDS.

    where n=3-4

  • 2. Do methylene malonates react with water?

    Unlike cyanoacrylates, methylene malonates do not polymerize on contact with water. Our monomers have reasonable pot life when handled in deionized water. (Note: These monomers will polymerize when mixed with municipal tap water!) Methylene malonates will stay stable for a few hours: enough time to conduct a polymerization or a crosslinking reaction, after which a decrease in the alkene functionality due to Michael addition may take place. Even though stability of up to 12 hours has been observed, long-term storage in water is not recommended. Methylene malonates can be anionically polymerized in water within minutes. Please refer to US 9,249,265 and US 9,637,564 for examples of emulsion polymerization.

  • 3. What are the storage, safety and handling guidelines for methylene malonates?

    Please review the safety data sheets (SDS) for each product prior to use. Always provide proper ventilation and PPE when using methylene malonates. Store methylene malonates away from alkaline substances in a cool, dark place. We ship all samples with a stabilizer package intended to maintain room temperature stability for at least six months. However, it is generally recommended to store methylene malonates at temperatures from 0 to 5°C. Allow them to return to room temperature before each use to minimize condensation inside the storage container. Store the samples in unpigmented HDPE containers. Passivate all glassware with a weak acid solution (1% MSA in THF, followed by rinsing with dry acetone) before conducting desired reactions in glass. Long-term storage in glass is not recommended. Plastic pipettes are recommended for aliquots, and double dipping of the pipette is not advisable as it may have contacted basic initiating species. Should you have further questions, please consult your Sirrus representative.

  • 4. What inhibitors are used with methylene malonates?

    Methylene malonates are stabilized with methanesulfonic acid (MSA) and butylated hydroxytoluene (BHT). Information on the levels of inhibitors used in each product can be found in the TDS and certificates of analysis.

  • 5. What types of methylene malonates have been synthesized?

    Both symmetric and asymmetric diesters have been successfully synthesized and characterized. We have also demonstrated the synthesis of ketoesters and difunctional and multifunctional methylene malonate polyesters.

  • 6. Can PEGs be used to functionalize Sirrus materials?

    We have prepared several “PEGylated” monofunctional and multifunctional monomers via transesterification. These compounds have been shown to have hydrophilic when cured as a coating on a substrate.

  • 7. Is passivation necessary when using methylene malonates?

    Acid pre-treatment or passivation is recommended for all equipment used to process, store and transport methylene malonates to prevent bulk anionic polymerization. We passivate all glassware and equipment used to handle methylene malonates with 1% solution of methanesulfonic acid in THF followed by three rinses with dry acetone.

  • 8. Which solvents can be used for dilution of methylene malonates?

    Our methylene malonate monomers have low viscosity, so dilution is not required for most applications. However, for higher viscosity formulations, a solvent can be included in formulations for application purposes. Methylene malonates are compatible with esters and ketones. Butyl acetate and glycol ether PM acetate can be used. Alcohols should be avoided as they can readily Michael add across the double bond.

  • 9. What are the Hansen Solubility Parameters for methylene malonates?
    δD, MPa½ δP, MPa½ δH, MPa½
    Chemilian® M1000 XP 16.24 5.31 6.56
    Chemilian® L3000 XP 16.28 3.31 4.37
    Chemilian® H4000 XP 17.4 3.28 4.63
    Forza® B5200 XP 16.28 4.15 5.67
  • 10. What is the functionality of Forza® B5200 XP?

    The functionality of Forza® B5200 XP can be calculated based on the assumption of the molecular weight of the repeating unit as 170 g/mol. This unit includes the residue of 1,4-butanediol and of one methylene malonate functional group. A correction for Michael adducts is done via the use of Alkene Number (AN), which is obtained by quantitative NMR for every lot of this product. The functionality (f) can then be obtained from the following equation:

    $$ \large{\mathsf{ƒ=\mathit{M_n}*\frac{\mathit{AN}}{17,000} }} $$

    For example, for a lot of product with Mn=900 g/mol and AN=75, the functionality: 

    $$ \large{\mathsf{ƒ=900*\frac{75}{17,000} }=3.97} $$

ANIONIC POLYMERIZATION

  • 11. Which initiators can be used for anionic polymerization of methylene malonates?

    Weak and strong bases and nucleophiles initiate anionic polymerization of methylene malonates. Sodium benzoate and other sodium salts of carboxylic acids work well. Potassium or calcium benzoates, carbonates and pyruvates have also been demonstrated to be initiators. Secondary and tertiary amines will initiate anionic polymerization. N,N,N’,N’-Tetramethylguanidine (TMG) and 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) have been demonstrated as some of the fastest anionic initiators in bulk and solution polymerization. Many organometallic compounds can initiate methylene malonates including commonly used catalysts such as dibutyltin dilaurate (DBTDL).

  • 12. What molecular weight can be obtained in anionic polymerization of methylene malonate monomers?

    For polymerization in solutions, molecular weights can be controlled by varying the initiator concentration as well as initiator choice and type of the solvent. Block copolymers and random copolymers can be built with controlled architecture under low temperatures. In our laboratories, weight average molecular weights of more than 106 Da were shown to be possible. Please refer to US 9,279,022 for examples of anionic polymerization of various methylene malonate monomers.

  • 13. Has Sirrus demonstrated the ability to create block copolymers? For example, AAABBB?

    Yes. Typically, sequential addition allowed us to control the sequence of monomer units in the polymer. At low temperature, chain-transfer side reactions are significantly reduced. We have synthesized diblock and triblock copolymers. Initiators used have been TMG, sodium benzoate and alkyl lithium initiators. The best results were demonstrated at temperatures less than 0°C.

  • 14. What polydispersity (PDI) has been obtained under lab conditions with methylene malonate monomers?

    We were able to obtain PDI as low as 1.05 when polymerization was initiated at low temperatures. Higher PDI was observed at room temperature and above, which was likely due to chain-transfer reactions.

  • 15. Is surface initiation possible with methylene malonates?

    Anionic polymerization can be initiated on a surface in the presence of an initiator. A polymer front is propagated that may be several microns thick. Testing by our partners has demonstrated best-in-class adhesion for methylene malonates polymerized using surface initiation on responsive (initiating) substrates. One proposed mechanism is that covalent bonds are forming between the surface and the polymer layer, thus drastically improving the adhesion.

    Glass may be an ideal surface to observe this behavior. Base coats formulated with amines or anionic surfactants also demonstrate strong surface initiation.

    Low-energy and difficult-to-adhere-to substrates like polypropylene are not inherently good initiators for anionic polymerization.

  • 16. Is it possible to chain terminate anionic polymerization?

    Yes. Anionic polymerization of methylene malonate monomers will end when all functionality has been consumed or a vitrification point has been reached. However, if the anionic polymer is left in solution without termination, lower molecular weight polymer may result until an equilibrium state has been achieved. For anionic polymerization, chain termination can be achieved with acids. We have used trifluoroacetic acid and methanesulfonic acid, as well as pyruvic acid, for chain termination in solution polymerization.

  • 17. What can be done to enhance the reactivity of substrate surfaces towards anionic polymerization of methylene malonates?

    We recommend nucleophilic primers (such as silanes or amines), as well as corona or plasma treatment that would either expose or produce hydroxyl or carboxylate functionality, and sanding in instances where initiators may lie below the substrate surface (e.g., glass-filled polypropylene).

MICHAEL ADDITION

  • 18. What can catalyze Michael addition for methylene malonates?

    Strong acids (e.g., methane sulfonic acid) that also suppress the anionic polymerization can catalyze Michael addition of methylene malonates. Zinc triflate can also initiate Michael addition. Michael addition can also slowly happen at room temperature without catalysis. Bases can also catalyze Michael addition, but they also initiate competing anionic polymerization.

  • 19. What is the mechanism of acid-catalyzed Michael addition for methylene malonates?

    Scroll right to see the full image →

  • 20. How do amines perform as Michael donors for methylene malonates?

    Primary and secondary amines will Michael add, although subsequent anionic polymerization is possible from the resultant secondary and tertiary amine adducts, respectively. Tertiary amines only catalyze anionic or zwitterionic polymerization. Amines like DBU and TMG have been demonstrated to be very strong anionic initiators. We believe that this is related to both nucleophilicity and pKb values. The behavior of initiators when mixed in bulk is often different from initiators used on a surface. These relationships are complex, so please contact your Sirrus representative for help with specific polymerization and application strategies. 

  • 21. What methylene malonate is recommended for cure with acrylic polyols?

    We recommend Forza® B5200 XP methylene malonate polyester to make copolymers with acrylic polyols. Clear coats have been prepared using Michael addition in combination with anionic cure. For efficient crosslinking using a hydroxyl group, multifunctional materials are recommended.

  • 22. Other than amine and hydroxyl functional groups, what may be used in a Michael addition with methylene malonates?

    Thiols can also be used for Michael addition to methylene malonates. Carboxylic acid salts including polymers with neutralized carboxylic acid groups can form Michael adducts as well as initiate anionic polymerization.

  • 23. What types of polymeric polyols have been shown to Michael add to methylene malonates?

    Polyester, acrylic and polyether polyols have been shown to react in Michael addition with methylene malonates.

  • 24. What stoichiometry is recommended for Michael addition cure with polyols?

    Michael addition of polyols to methylene malonates is often accompanied by anionic polymerization. Because of this it is best to determine the optimum ratio experimentally for each system.

RADICAL POLYMERIZATION

  • 25. What radical initiators can be used to polymerize methylene malonates?

    Commonly used peroxide and azo radical initiators will initiate radical polymerization for methylene malonates analogously to other activated alkenes. UV and visible light photoinitiators can also be used to initiate radical polymerization.

  • 26. Is the addition of free radical stabilizers necessary when formulating with methylene malonates?

    Bulk free radical polymerization is possible with methylene malonates. All of our products contain free radical stabilizers. It is a good practice to use additional free radical stabilizers to assure stability against free radical polymerization during formulation and handling of the formulations containing methylene malonates. Care must be taken when considering other stabilizers such as hindered amine light stabilizers (HALS), as some amines may initiate methylene malonates anionically.

  • 27. Are methylene malonates compatible with (meth)acrylates used in UV cure?

    A. Methylene malonates are much more reactive towards weak bases than (meth)acrylates. Therefore, care must be taken as residual catalysts from the synthesis of (meth)acrylates (i.e. DBTDL used in the synthesis of polyurethane acrylates) and the basic functional groups of some (meth)acrylates (i.e. tertiary amine and OH groups) and their levels may impact stability of the blends with methylene malonates. Due to the great number of (meth)acrylates being available from multiple suppliers it is easier to test for compatibility with methylene malonates rather than trying to rely on predictions based on structure reactivity relationships. For example, a bisphenol A methacrylate CN 154 showed viscosity increase upon storage as a blend with 80% Chemilian® H4000 XP (dicyclohexyl methylene malonate or DCHMM). The blend was stabilized by the addition of 100ppm of methanesulfonic acid (MSA) and had no noticeable viscosity increase after 2 weeks at 50C. Analogously, a blend of Chemilian® H4000 XP with 20% of aliphatic urethane acrylate CN991 was also stabilized with 100ppm MSA. Passivation of the mixing equipment coupled with the addition of small quantities of MSA to the blends are the simplest approaches to improve stability.